Functions and Operators

From: Andrew Dunstan Date: Mon, 4 Aug 2025 12:56:48 +0000 (-0400) Subject: Split func.sgml into more manageable pieces X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4e23c9ef65accde7eb3e56aa28d50ae5cf79b64b;p=thirdparty%2Fpostgresql.git Split func.sgml into more manageable pieces func.sgml has grown over the years to the point where it is very difficult to manage. This commit splits out each sect1 piece into its own file, which is then included in the main file, so that the built documentation should be identical to the pre-split documentation. All these new files are placed in a new "func" subdirectory, and the previous func.sgml is removed. Done using scripts developed by: Author: jian he Discussion: https://postgr.es/m/CACJufxFgAh1--EMwOjMuANe=VTmjkNaZjH+AzSe04-8ZCGiESA@mail.gmail.com --- diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml index bcde3cfd037..ac66fcbdb57 100644 --- a/doc/src/sgml/filelist.sgml +++ b/doc/src/sgml/filelist.sgml @@ -17,7 +17,10 @@ - + + +%allfiles_func; + diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml deleted file mode 100644 index 74a16af04ad..00000000000 --- a/doc/src/sgml/func.sgml +++ /dev/null @@ -1,32075 +0,0 @@ - - - - Functions and Operators - - - function - - - - operator - - - - PostgreSQL provides a large number of - functions and operators for the built-in data types. This chapter - describes most of them, although additional special-purpose functions - appear in relevant sections of the manual. Users can also - define their own functions and operators, as described in - . The - psql commands \df and - \do can be used to list all - available functions and operators, respectively. - - - - The notation used throughout this chapter to describe the argument and - result data types of a function or operator is like this: - -repeat ( text, integer ) text - - which says that the function repeat takes one text and - one integer argument and returns a result of type text. The right arrow - is also used to indicate the result of an example, thus: - -repeat('Pg', 4) PgPgPgPg - - - - - If you are concerned about portability then note that most of - the functions and operators described in this chapter, with the - exception of the most trivial arithmetic and comparison operators - and some explicitly marked functions, are not specified by the - SQL standard. Some of this extended functionality - is present in other SQL database management - systems, and in many cases this functionality is compatible and - consistent between the various implementations. - - - - - Logical Operators - - - operator - logical - - - - Boolean - operators - operators, logical - - - - The usual logical operators are available: - - - AND (operator) - - - - OR (operator) - - - - NOT (operator) - - - - conjunction - - - - disjunction - - - - negation - - - -boolean AND boolean boolean -boolean OR boolean boolean -NOT boolean boolean - - - SQL uses a three-valued logic system with true, - false, and null, which represents unknown. - Observe the following truth tables: - - - - - - a - b - a AND b - a OR b - - - - - - TRUE - TRUE - TRUE - TRUE - - - - TRUE - FALSE - FALSE - TRUE - - - - TRUE - NULL - NULL - TRUE - - - - FALSE - FALSE - FALSE - FALSE - - - - FALSE - NULL - FALSE - NULL - - - - NULL - NULL - NULL - NULL - - - - - - - - - - a - NOT a - - - - - - TRUE - FALSE - - - - FALSE - TRUE - - - - NULL - NULL - - - - - - - - The operators AND and OR are - commutative, that is, you can switch the left and right operands - without affecting the result. (However, it is not guaranteed that - the left operand is evaluated before the right operand. See for more information about the - order of evaluation of subexpressions.) - - - - - Comparison Functions and Operators - - - comparison - operators - - - - The usual comparison operators are available, as shown in . - - - - Comparison Operators - - - - Operator - Description - - - - - - - datatype < datatype - boolean - - Less than - - - - - datatype > datatype - boolean - - Greater than - - - - - datatype <= datatype - boolean - - Less than or equal to - - - - - datatype >= datatype - boolean - - Greater than or equal to - - - - - datatype = datatype - boolean - - Equal - - - - - datatype <> datatype - boolean - - Not equal - - - - - datatype != datatype - boolean - - Not equal - - - -

- - - - <> is the standard SQL notation for not - equal. != is an alias, which is converted - to <> at a very early stage of parsing. - Hence, it is not possible to implement != - and <> operators that do different things. - - - - - These comparison operators are available for all built-in data types - that have a natural ordering, including numeric, string, and date/time - types. In addition, arrays, composite types, and ranges can be compared - if their component data types are comparable. - - - - It is usually possible to compare values of related data - types as well; for example integer > - bigint will work. Some cases of this sort are implemented - directly by cross-type comparison operators, but if no - such operator is available, the parser will coerce the less-general type - to the more-general type and apply the latter's comparison operator. - - - - As shown above, all comparison operators are binary operators that - return values of type boolean. Thus, expressions like - 1 < 2 < 3 are not valid (because there is - no < operator to compare a Boolean value with - 3). Use the BETWEEN predicates - shown below to perform range tests. - - - - There are also some comparison predicates, as shown in . These behave much like - operators, but have special syntax mandated by the SQL standard. - - - - Comparison Predicates - - - - - Predicate - - - Description - - - Example(s) - - - - - - - - datatype BETWEEN datatype AND datatype - boolean - - - Between (inclusive of the range endpoints). - - - 2 BETWEEN 1 AND 3 - t - - - 2 BETWEEN 3 AND 1 - f - - - - - - datatype NOT BETWEEN datatype AND datatype - boolean - - - Not between (the negation of BETWEEN). - - - 2 NOT BETWEEN 1 AND 3 - f - - - - - - datatype BETWEEN SYMMETRIC datatype AND datatype - boolean - - - Between, after sorting the two endpoint values. - - - 2 BETWEEN SYMMETRIC 3 AND 1 - t - - - - - - datatype NOT BETWEEN SYMMETRIC datatype AND datatype - boolean - - - Not between, after sorting the two endpoint values. - - - 2 NOT BETWEEN SYMMETRIC 3 AND 1 - f - - - - - - datatype IS DISTINCT FROM datatype - boolean - - - Not equal, treating null as a comparable value. - - - 1 IS DISTINCT FROM NULL - t (rather than NULL) - - - NULL IS DISTINCT FROM NULL - f (rather than NULL) - - - - - - datatype IS NOT DISTINCT FROM datatype - boolean - - - Equal, treating null as a comparable value. - - - 1 IS NOT DISTINCT FROM NULL - f (rather than NULL) - - - NULL IS NOT DISTINCT FROM NULL - t (rather than NULL) - - - - - - datatype IS NULL - boolean - - - Test whether value is null. - - - 1.5 IS NULL - f - - - - - - datatype IS NOT NULL - boolean - - - Test whether value is not null. - - - 'null' IS NOT NULL - t - - - - - - datatype ISNULL - boolean - - - Test whether value is null (nonstandard syntax). - - - - - - datatype NOTNULL - boolean - - - Test whether value is not null (nonstandard syntax). - - - - - - boolean IS TRUE - boolean - - - Test whether boolean expression yields true. - - - true IS TRUE - t - - - NULL::boolean IS TRUE - f (rather than NULL) - - - - - - boolean IS NOT TRUE - boolean - - - Test whether boolean expression yields false or unknown. - - - true IS NOT TRUE - f - - - NULL::boolean IS NOT TRUE - t (rather than NULL) - - - - - - boolean IS FALSE - boolean - - - Test whether boolean expression yields false. - - - true IS FALSE - f - - - NULL::boolean IS FALSE - f (rather than NULL) - - - - - - boolean IS NOT FALSE - boolean - - - Test whether boolean expression yields true or unknown. - - - true IS NOT FALSE - t - - - NULL::boolean IS NOT FALSE - t (rather than NULL) - - - - - - boolean IS UNKNOWN - boolean - - - Test whether boolean expression yields unknown. - - - true IS UNKNOWN - f - - - NULL::boolean IS UNKNOWN - t (rather than NULL) - - - - - - boolean IS NOT UNKNOWN - boolean - - - Test whether boolean expression yields true or false. - - - true IS NOT UNKNOWN - t - - - NULL::boolean IS NOT UNKNOWN - f (rather than NULL) - - - - -

- - - - BETWEEN - - - BETWEEN SYMMETRIC - - The BETWEEN predicate simplifies range tests: - -a BETWEEN x AND y - - is equivalent to - -a >= x AND a <= y - - Notice that BETWEEN treats the endpoint values as included - in the range. - BETWEEN SYMMETRIC is like BETWEEN - except there is no requirement that the argument to the left of - AND be less than or equal to the argument on the right. - If it is not, those two arguments are automatically swapped, so that - a nonempty range is always implied. - - - - The various variants of BETWEEN are implemented in - terms of the ordinary comparison operators, and therefore will work for - any data type(s) that can be compared. - - - - - The use of AND in the BETWEEN - syntax creates an ambiguity with the use of AND as a - logical operator. To resolve this, only a limited set of expression - types are allowed as the second argument of a BETWEEN - clause. If you need to write a more complex sub-expression - in BETWEEN, write parentheses around the - sub-expression. - - - - - - IS DISTINCT FROM - - - IS NOT DISTINCT FROM - - Ordinary comparison operators yield null (signifying unknown), - not true or false, when either input is null. For example, - 7 = NULL yields null, as does 7 <> NULL. When - this behavior is not suitable, use the - IS NOT DISTINCT FROM predicates: - -a IS DISTINCT FROM b -a IS NOT DISTINCT FROM b - - For non-null inputs, IS DISTINCT FROM is - the same as the <> operator. However, if both - inputs are null it returns false, and if only one input is - null it returns true. Similarly, IS NOT DISTINCT - FROM is identical to = for non-null - inputs, but it returns true when both inputs are null, and false when only - one input is null. Thus, these predicates effectively act as though null - were a normal data value, rather than unknown. - - - - - IS NULL - - - IS NOT NULL - - - ISNULL - - - NOTNULL - - To check whether a value is or is not null, use the predicates: - -expression IS NULL -expression IS NOT NULL - - or the equivalent, but nonstandard, predicates: - -expression ISNULL -expression NOTNULL - - null valuecomparing - - - - Do not write - expression = NULL - because NULL is not equal to - NULL. (The null value represents an unknown value, - and it is not known whether two unknown values are equal.) - - - - - Some applications might expect that - expression = NULL - returns true if expression evaluates to - the null value. It is highly recommended that these applications - be modified to comply with the SQL standard. However, if that - cannot be done the - configuration variable is available. If it is enabled, - PostgreSQL will convert x = - NULL clauses to x IS NULL. - - - - - If the expression is row-valued, then - IS NULL is true when the row expression itself is null - or when all the row's fields are null, while - IS NOT NULL is true when the row expression itself is non-null - and all the row's fields are non-null. Because of this behavior, - IS NULL and IS NOT NULL do not always return - inverse results for row-valued expressions; in particular, a row-valued - expression that contains both null and non-null fields will return false - for both tests. For example: - - -SELECT ROW(1,2.5,'this is a test') = ROW(1, 3, 'not the same'); - -SELECT ROW(table.*) IS NULL FROM table; -- detect all-null rows - -SELECT ROW(table.*) IS NOT NULL FROM table; -- detect all-non-null rows - -SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in rows - - - In some cases, it may be preferable to - write row IS DISTINCT FROM NULL - or row IS NOT DISTINCT FROM NULL, - which will simply check whether the overall row value is null without any - additional tests on the row fields. - - - - - IS TRUE - - - IS NOT TRUE - - - IS FALSE - - - IS NOT FALSE - - - IS UNKNOWN - - - IS NOT UNKNOWN - - Boolean values can also be tested using the predicates - -boolean_expression IS TRUE -boolean_expression IS NOT TRUE -boolean_expression IS FALSE -boolean_expression IS NOT FALSE -boolean_expression IS UNKNOWN -boolean_expression IS NOT UNKNOWN - - These will always return true or false, never a null value, even when the - operand is null. - A null input is treated as the logical value unknown. - Notice that IS UNKNOWN and IS NOT UNKNOWN are - effectively the same as IS NULL and - IS NOT NULL, respectively, except that the input - expression must be of Boolean type. - - - - Some comparison-related functions are also available, as shown in . - - - - Comparison Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - num_nonnulls - - num_nonnulls ( VARIADIC "any" ) - integer - - - Returns the number of non-null arguments. - - - num_nonnulls(1, NULL, 2) - 2 - - - - - - num_nulls - - num_nulls ( VARIADIC "any" ) - integer - - - Returns the number of null arguments. - - - num_nulls(1, NULL, 2) - 1 - - - - -

- - - - - Mathematical Functions and Operators - - - Mathematical operators are provided for many - PostgreSQL types. For types without - standard mathematical conventions - (e.g., date/time types) we - describe the actual behavior in subsequent sections. - - - - shows the mathematical - operators that are available for the standard numeric types. - Unless otherwise noted, operators shown as - accepting numeric_type are available for all - the types smallint, integer, - bigint, numeric, real, - and double precision. - Operators shown as accepting integral_type - are available for the types smallint, integer, - and bigint. - Except where noted, each form of an operator returns the same data type - as its argument(s). Calls involving multiple argument data types, such - as integer + numeric, - are resolved by using the type appearing later in these lists. - - - - Mathematical Operators - - - - - - Operator - - - Description - - - Example(s) - - - - - - - - numeric_type + numeric_type - numeric_type - - - Addition - - - 2 + 3 - 5 - - - - - - + numeric_type - numeric_type - - - Unary plus (no operation) - - - + 3.5 - 3.5 - - - - - - numeric_type - numeric_type - numeric_type - - - Subtraction - - - 2 - 3 - -1 - - - - - - - numeric_type - numeric_type - - - Negation - - - - (-4) - 4 - - - - - - numeric_type * numeric_type - numeric_type - - - Multiplication - - - 2 * 3 - 6 - - - - - - numeric_type / numeric_type - numeric_type - - - Division (for integral types, division truncates the result towards - zero) - - - 5.0 / 2 - 2.5000000000000000 - - - 5 / 2 - 2 - - - (-5) / 2 - -2 - - - - - - numeric_type % numeric_type - numeric_type - - - Modulo (remainder); available for smallint, - integer, bigint, and numeric - - - 5 % 4 - 1 - - - - - - numeric ^ numeric - numeric - - - double precision ^ double precision - double precision - - - Exponentiation - - - 2 ^ 3 - 8 - - - Unlike typical mathematical practice, multiple uses of - ^ will associate left to right by default: - - - 2 ^ 3 ^ 3 - 512 - - - 2 ^ (3 ^ 3) - 134217728 - - - - - - |/ double precision - double precision - - - Square root - - - |/ 25.0 - 5 - - - - - - ||/ double precision - double precision - - - Cube root - - - ||/ 64.0 - 4 - - - - - - @ numeric_type - numeric_type - - - Absolute value - - - @ -5.0 - 5.0 - - - - - - integral_type & integral_type - integral_type - - - Bitwise AND - - - 91 & 15 - 11 - - - - - - integral_type | integral_type - integral_type - - - Bitwise OR - - - 32 | 3 - 35 - - - - - - integral_type # integral_type - integral_type - - - Bitwise exclusive OR - - - 17 # 5 - 20 - - - - - - ~ integral_type - integral_type - - - Bitwise NOT - - - ~1 - -2 - - - - - - integral_type << integer - integral_type - - - Bitwise shift left - - - 1 << 4 - 16 - - - - - - integral_type >> integer - integral_type - - - Bitwise shift right - - - 8 >> 2 - 2 - - - - - -

- - - shows the available - mathematical functions. - Many of these functions are provided in multiple forms with different - argument types. - Except where noted, any given form of a function returns the same - data type as its argument(s); cross-type cases are resolved in the - same way as explained above for operators. - The functions working with double precision data are mostly - implemented on top of the host system's C library; accuracy and behavior in - boundary cases can therefore vary depending on the host system. - - - - Mathematical Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - abs - - abs ( numeric_type ) - numeric_type - - - Absolute value - - - abs(-17.4) - 17.4 - - - - - - - cbrt - - cbrt ( double precision ) - double precision - - - Cube root - - - cbrt(64.0) - 4 - - - - - - - ceil - - ceil ( numeric ) - numeric - - - ceil ( double precision ) - double precision - - - Nearest integer greater than or equal to argument - - - ceil(42.2) - 43 - - - ceil(-42.8) - -42 - - - - - - - ceiling - - ceiling ( numeric ) - numeric - - - ceiling ( double precision ) - double precision - - - Nearest integer greater than or equal to argument (same - as ceil) - - - ceiling(95.3) - 96 - - - - - - - degrees - - degrees ( double precision ) - double precision - - - Converts radians to degrees - - - degrees(0.5) - 28.64788975654116 - - - - - - - div - - div ( y numeric, - x numeric ) - numeric - - - Integer quotient of y/x - (truncates towards zero) - - - div(9, 4) - 2 - - - - - - - erf - - erf ( double precision ) - double precision - - - Error function - - - erf(1.0) - 0.8427007929497149 - - - - - - - erfc - - erfc ( double precision ) - double precision - - - Complementary error function (1 - erf(x), without - loss of precision for large inputs) - - - erfc(1.0) - 0.15729920705028513 - - - - - - - exp - - exp ( numeric ) - numeric - - - exp ( double precision ) - double precision - - - Exponential (e raised to the given power) - - - exp(1.0) - 2.7182818284590452 - - - - - - - factorial - - factorial ( bigint ) - numeric - - - Factorial - - - factorial(5) - 120 - - - - - - - floor - - floor ( numeric ) - numeric - - - floor ( double precision ) - double precision - - - Nearest integer less than or equal to argument - - - floor(42.8) - 42 - - - floor(-42.8) - -43 - - - - - - - gamma - - gamma ( double precision ) - double precision - - - Gamma function - - - gamma(0.5) - 1.772453850905516 - - - gamma(6) - 120 - - - - - - - gcd - - gcd ( numeric_type, numeric_type ) - numeric_type - - - Greatest common divisor (the largest positive number that divides both - inputs with no remainder); returns 0 if both inputs - are zero; available for integer, bigint, - and numeric - - - gcd(1071, 462) - 21 - - - - - - - lcm - - lcm ( numeric_type, numeric_type ) - numeric_type - - - Least common multiple (the smallest strictly positive number that is - an integral multiple of both inputs); returns 0 if - either input is zero; available for integer, - bigint, and numeric - - - lcm(1071, 462) - 23562 - - - - - - - lgamma - - lgamma ( double precision ) - double precision - - - Natural logarithm of the absolute value of the gamma function - - - lgamma(1000) - 5905.220423209181 - - - - - - - ln - - ln ( numeric ) - numeric - - - ln ( double precision ) - double precision - - - Natural logarithm - - - ln(2.0) - 0.6931471805599453 - - - - - - - log - - log ( numeric ) - numeric - - - log ( double precision ) - double precision - - - Base 10 logarithm - - - log(100) - 2 - - - - - - - log10 - - log10 ( numeric ) - numeric - - - log10 ( double precision ) - double precision - - - Base 10 logarithm (same as log) - - - log10(1000) - 3 - - - - - - log ( b numeric, - x numeric ) - numeric - - - Logarithm of x to base b - - - log(2.0, 64.0) - 6.0000000000000000 - - - - - - - min_scale - - min_scale ( numeric ) - integer - - - Minimum scale (number of fractional decimal digits) needed - to represent the supplied value precisely - - - min_scale(8.4100) - 2 - - - - - - - mod - - mod ( y numeric_type, - x numeric_type ) - numeric_type - - - Remainder of y/x; - available for smallint, integer, - bigint, and numeric - - - mod(9, 4) - 1 - - - - - - - pi - - pi ( ) - double precision - - - Approximate value of π - - - pi() - 3.141592653589793 - - - - - - - power - - power ( a numeric, - b numeric ) - numeric - - - power ( a double precision, - b double precision ) - double precision - - - a raised to the power of b - - - power(9, 3) - 729 - - - - - - - radians - - radians ( double precision ) - double precision - - - Converts degrees to radians - - - radians(45.0) - 0.7853981633974483 - - - - - - - round - - round ( numeric ) - numeric - - - round ( double precision ) - double precision - - - Rounds to nearest integer. For numeric, ties are - broken by rounding away from zero. For double precision, - the tie-breaking behavior is platform dependent, but - round to nearest even is the most common rule. - - - round(42.4) - 42 - - - - - - round ( v numeric, s integer ) - numeric - - - Rounds v to s decimal - places. Ties are broken by rounding away from zero. - - - round(42.4382, 2) - 42.44 - - - round(1234.56, -1) - 1230 - - - - - - - scale - - scale ( numeric ) - integer - - - Scale of the argument (the number of decimal digits in the fractional part) - - - scale(8.4100) - 4 - - - - - - - sign - - sign ( numeric ) - numeric - - - sign ( double precision ) - double precision - - - Sign of the argument (-1, 0, or +1) - - - sign(-8.4) - -1 - - - - - - - sqrt - - sqrt ( numeric ) - numeric - - - sqrt ( double precision ) - double precision - - - Square root - - - sqrt(2) - 1.4142135623730951 - - - - - - - trim_scale - - trim_scale ( numeric ) - numeric - - - Reduces the value's scale (number of fractional decimal digits) by - removing trailing zeroes - - - trim_scale(8.4100) - 8.41 - - - - - - - trunc - - trunc ( numeric ) - numeric - - - trunc ( double precision ) - double precision - - - Truncates to integer (towards zero) - - - trunc(42.8) - 42 - - - trunc(-42.8) - -42 - - - - - - trunc ( v numeric, s integer ) - numeric - - - Truncates v to s - decimal places - - - trunc(42.4382, 2) - 42.43 - - - - - - - width_bucket - - width_bucket ( operand numeric, low numeric, high numeric, count integer ) - integer - - - width_bucket ( operand double precision, low double precision, high double precision, count integer ) - integer - - - Returns the number of the bucket in - which operand falls in a histogram - having count equal-width buckets spanning the - range low to high. - The buckets have inclusive lower bounds and exclusive upper bounds. - Returns 0 for an input less - than low, - or count+1 for an input - greater than or equal to high. - If low > high, - the behavior is mirror-reversed, with bucket 1 - now being the one just below low, and the - inclusive bounds now being on the upper side. - - - width_bucket(5.35, 0.024, 10.06, 5) - 3 - - - width_bucket(9, 10, 0, 10) - 2 - - - - - - width_bucket ( operand anycompatible, thresholds anycompatiblearray ) - integer - - - Returns the number of the bucket in - which operand falls given an array listing the - inclusive lower bounds of the buckets. - Returns 0 for an input less than the first lower - bound. operand and the array elements can be - of any type having standard comparison operators. - The thresholds array must be - sorted, smallest first, or unexpected results will be - obtained. - - - width_bucket(now(), array['yesterday', 'today', 'tomorrow']::timestamptz[]) - 2 - - - - -

- - - shows functions for - generating random numbers. - - - - Random Functions - - - - - - Function - - - Description - - - Example(s) - - - - - - - - - random - - random ( ) - double precision - - - Returns a random value in the range 0.0 <= x < 1.0 - - - random() - 0.897124072839091 - - - - - - - random - - random ( min integer, max integer ) - integer - - - random ( min bigint, max bigint ) - bigint - - - random ( min numeric, max numeric ) - numeric - - - Returns a random value in the range - min <= x <= max. - For type numeric, the result will have the same number of - fractional decimal digits as min or - max, whichever has more. - - - random(1, 10) - 7 - - - random(-0.499, 0.499) - 0.347 - - - - - - - random_normal - - - random_normal ( - mean double precision - , stddev double precision ) - double precision - - - Returns a random value from the normal distribution with the given - parameters; mean defaults to 0.0 - and stddev defaults to 1.0 - - - random_normal(0.0, 1.0) - 0.051285419 - - - - - - - setseed - - setseed ( double precision ) - void - - - Sets the seed for subsequent random() and - random_normal() calls; - argument must be between -1.0 and 1.0, inclusive - - - setseed(0.12345) - - - - -

- - - The random() and random_normal() - functions listed in use a - deterministic pseudo-random number generator. - It is fast but not suitable for cryptographic - applications; see the module for a more - secure alternative. - If setseed() is called, the series of results of - subsequent calls to these functions in the current session - can be repeated by re-issuing setseed() with the same - argument. - Without any prior setseed() call in the same - session, the first call to any of these functions obtains a seed - from a platform-dependent source of random bits. - - - - shows the - available trigonometric functions. Each of these functions comes in - two variants, one that measures angles in radians and one that - measures angles in degrees. - - - - Trigonometric Functions - - - - - - Function - - - Description - - - Example(s) - - - - - - - - - acos - - acos ( double precision ) - double precision - - - Inverse cosine, result in radians - - - acos(1) - 0 - - - - - - - acosd - - acosd ( double precision ) - double precision - - - Inverse cosine, result in degrees - - - acosd(0.5) - 60 - - - - - - - asin - - asin ( double precision ) - double precision - - - Inverse sine, result in radians - - - asin(1) - 1.5707963267948966 - - - - - - - asind - - asind ( double precision ) - double precision - - - Inverse sine, result in degrees - - - asind(0.5) - 30 - - - - - - - atan - - atan ( double precision ) - double precision - - - Inverse tangent, result in radians - - - atan(1) - 0.7853981633974483 - - - - - - - atand - - atand ( double precision ) - double precision - - - Inverse tangent, result in degrees - - - atand(1) - 45 - - - - - - - atan2 - - atan2 ( y double precision, - x double precision ) - double precision - - - Inverse tangent of - y/x, - result in radians - - - atan2(1, 0) - 1.5707963267948966 - - - - - - - atan2d - - atan2d ( y double precision, - x double precision ) - double precision - - - Inverse tangent of - y/x, - result in degrees - - - atan2d(1, 0) - 90 - - - - - - - cos - - cos ( double precision ) - double precision - - - Cosine, argument in radians - - - cos(0) - 1 - - - - - - - cosd - - cosd ( double precision ) - double precision - - - Cosine, argument in degrees - - - cosd(60) - 0.5 - - - - - - - cot - - cot ( double precision ) - double precision - - - Cotangent, argument in radians - - - cot(0.5) - 1.830487721712452 - - - - - - - cotd - - cotd ( double precision ) - double precision - - - Cotangent, argument in degrees - - - cotd(45) - 1 - - - - - - - sin - - sin ( double precision ) - double precision - - - Sine, argument in radians - - - sin(1) - 0.8414709848078965 - - - - - - - sind - - sind ( double precision ) - double precision - - - Sine, argument in degrees - - - sind(30) - 0.5 - - - - - - - tan - - tan ( double precision ) - double precision - - - Tangent, argument in radians - - - tan(1) - 1.5574077246549023 - - - - - - - tand - - tand ( double precision ) - double precision - - - Tangent, argument in degrees - - - tand(45) - 1 - - - - -

- - - - Another way to work with angles measured in degrees is to use the unit - transformation functions radians() - and degrees() shown earlier. - However, using the degree-based trigonometric functions is preferred, - as that way avoids round-off error for special cases such - as sind(30). - - - - - shows the - available hyperbolic functions. - - - - Hyperbolic Functions - - - - - - Function - - - Description - - - Example(s) - - - - - - - - - sinh - - sinh ( double precision ) - double precision - - - Hyperbolic sine - - - sinh(1) - 1.1752011936438014 - - - - - - - cosh - - cosh ( double precision ) - double precision - - - Hyperbolic cosine - - - cosh(0) - 1 - - - - - - - tanh - - tanh ( double precision ) - double precision - - - Hyperbolic tangent - - - tanh(1) - 0.7615941559557649 - - - - - - - asinh - - asinh ( double precision ) - double precision - - - Inverse hyperbolic sine - - - asinh(1) - 0.881373587019543 - - - - - - - acosh - - acosh ( double precision ) - double precision - - - Inverse hyperbolic cosine - - - acosh(1) - 0 - - - - - - - atanh - - atanh ( double precision ) - double precision - - - Inverse hyperbolic tangent - - - atanh(0.5) - 0.5493061443340548 - - - - -

- - - - - - String Functions and Operators - - - This section describes functions and operators for examining and - manipulating string values. Strings in this context include values - of the types character, character varying, - and text. Except where noted, these functions and operators - are declared to accept and return type text. They will - interchangeably accept character varying arguments. - Values of type character will be converted - to text before the function or operator is applied, resulting - in stripping any trailing spaces in the character value. - - - - SQL defines some string functions that use - key words, rather than commas, to separate - arguments. Details are in - . - PostgreSQL also provides versions of these functions - that use the regular function invocation syntax - (see ). - - - - - The string concatenation operator (||) will accept - non-string input, so long as at least one input is of string type, as shown - in . For other cases, inserting an - explicit coercion to text can be used to have non-string input - accepted. - - - - - <acronym>SQL</acronym> String Functions and Operators - - - - - Function/Operator - - - Description - - - Example(s) - - - - - - - - - character string - concatenation - - text || text - text - - - Concatenates the two strings. - - - 'Post' || 'greSQL' - PostgreSQL - - - - - - text || anynonarray - text - - - anynonarray || text - text - - - Converts the non-string input to text, then concatenates the two - strings. (The non-string input cannot be of an array type, because - that would create ambiguity with the array || - operators. If you want to concatenate an array's text equivalent, - cast it to text explicitly.) - - - 'Value: ' || 42 - Value: 42 - - - - - - - btrim - - btrim ( string text - , characters text ) - text - - - Removes the longest string containing only characters - in characters (a space by default) - from the start and end of string. - - - btrim('xyxtrimyyx', 'xyz') - trim - - - - - - - normalized - - - Unicode normalization - - text IS NOT form NORMALIZED - boolean - - - Checks whether the string is in the specified Unicode normalization - form. The optional form key word specifies the - form: NFC (the default), NFD, - NFKC, or NFKD. This expression can - only be used when the server encoding is UTF8. Note - that checking for normalization using this expression is often faster - than normalizing possibly already normalized strings. - - - U&'\0061\0308bc' IS NFD NORMALIZED - t - - - - - - - bit_length - - bit_length ( text ) - integer - - - Returns number of bits in the string (8 - times the octet_length). - - - bit_length('jose') - 32 - - - - - - - char_length - - - character string - length - - - length - of a character string - character string, length - - char_length ( text ) - integer - - - - character_length - - character_length ( text ) - integer - - - Returns number of characters in the string. - - - char_length('josé') - 4 - - - - - - - lower - - lower ( text ) - text - - - Converts the string to all lower case, according to the rules of the - database's locale. - - - lower('TOM') - tom - - - - - - - lpad - - lpad ( string text, - length integer - , fill text ) - text - - - Extends the string to length - length by prepending the characters - fill (a space by default). If the - string is already longer than - length then it is truncated (on the right). - - - lpad('hi', 5, 'xy') - xyxhi - - - - - - - ltrim - - ltrim ( string text - , characters text ) - text - - - Removes the longest string containing only characters in - characters (a space by default) from the start of - string. - - - ltrim('zzzytest', 'xyz') - test - - - - - - - normalize - - - Unicode normalization - - normalize ( text - , form ) - text - - - Converts the string to the specified Unicode - normalization form. The optional form key word - specifies the form: NFC (the default), - NFD, NFKC, or - NFKD. This function can only be used when the - server encoding is UTF8. - - - normalize(U&'\0061\0308bc', NFC) - U&'\00E4bc' - - - - - - - octet_length - - octet_length ( text ) - integer - - - Returns number of bytes in the string. - - - octet_length('josé') - 5 (if server encoding is UTF8) - - - - - - - octet_length - - octet_length ( character ) - integer - - - Returns number of bytes in the string. Since this version of the - function accepts type character directly, it will not - strip trailing spaces. - - - octet_length('abc '::character(4)) - 4 - - - - - - - overlay - - overlay ( string text PLACING newsubstring text FROM start integer FOR count integer ) - text - - - Replaces the substring of string that starts at - the start'th character and extends - for count characters - with newsubstring. - If count is omitted, it defaults to the length - of newsubstring. - - - overlay('Txxxxas' placing 'hom' from 2 for 4) - Thomas - - - - - - - position - - position ( substring text IN string text ) - integer - - - Returns first starting index of the specified - substring within - string, or zero if it's not present. - - - position('om' in 'Thomas') - 3 - - - - - - - rpad - - rpad ( string text, - length integer - , fill text ) - text - - - Extends the string to length - length by appending the characters - fill (a space by default). If the - string is already longer than - length then it is truncated. - - - rpad('hi', 5, 'xy') - hixyx - - - - - - - rtrim - - rtrim ( string text - , characters text ) - text - - - Removes the longest string containing only characters in - characters (a space by default) from the end of - string. - - - rtrim('testxxzx', 'xyz') - test - - - - - - - substring - - substring ( string text FROM start integer FOR count integer ) - text - - - Extracts the substring of string starting at - the start'th character if that is specified, - and stopping after count characters if that is - specified. Provide at least one of start - and count. - - - substring('Thomas' from 2 for 3) - hom - - - substring('Thomas' from 3) - omas - - - substring('Thomas' for 2) - Th - - - - - - substring ( string text FROM pattern text ) - text - - - Extracts the first substring matching POSIX regular expression; see - . - - - substring('Thomas' from '...$') - mas - - - - - - substring ( string text SIMILAR pattern text ESCAPE escape text ) - text - - - substring ( string text FROM pattern text FOR escape text ) - text - - - Extracts the first substring matching SQL regular expression; - see . The first form has - been specified since SQL:2003; the second form was only in SQL:1999 - and should be considered obsolete. - - - substring('Thomas' similar '%#"o_a#"_' escape '#') - oma - - - - - - - trim - - trim ( LEADING | TRAILING | BOTH - characters text FROM - string text ) - text - - - Removes the longest string containing only characters in - characters (a space by default) from the - start, end, or both ends (BOTH is the default) - of string. - - - trim(both 'xyz' from 'yxTomxx') - Tom - - - - - - trim ( LEADING | TRAILING | BOTH FROM - string text , - characters text ) - text - - - This is a non-standard syntax for trim(). - - - trim(both from 'yxTomxx', 'xyz') - Tom - - - - - - - unicode_assigned - - unicode_assigned ( text ) - boolean - - - Returns true if all characters in the string are - assigned Unicode codepoints; false otherwise. This - function can only be used when the server encoding is - UTF8. - - - - - - - upper - - upper ( text ) - text - - - Converts the string to all upper case, according to the rules of the - database's locale. - - - upper('tom') - TOM - - - - -

- - - Additional string manipulation functions and operators are available - and are listed in . (Some of - these are used internally to implement - the SQL-standard string functions listed in - .) - There are also pattern-matching operators, which are described in - , and operators for full-text - search, which are described in . - - - - Other String Functions and Operators - - - - - Function/Operator - - - Description - - - Example(s) - - - - - - - - - character string - prefix test - - text ^@ text - boolean - - - Returns true if the first string starts with the second string - (equivalent to the starts_with() function). - - - 'alphabet' ^@ 'alph' - t - - - - - - - ascii - - ascii ( text ) - integer - - - Returns the numeric code of the first character of the argument. - In UTF8 encoding, returns the Unicode code point - of the character. In other multibyte encodings, the argument must - be an ASCII character. - - - ascii('x') - 120 - - - - - - - chr - - chr ( integer ) - text - - - Returns the character with the given code. In UTF8 - encoding the argument is treated as a Unicode code point. In other - multibyte encodings the argument must designate - an ASCII character. chr(0) is - disallowed because text data types cannot store that character. - - - chr(65) - A - - - - - - - concat - - concat ( val1 "any" - , val2 "any" , ... ) - text - - - Concatenates the text representations of all the arguments. - NULL arguments are ignored. - - - concat('abcde', 2, NULL, 22) - abcde222 - - - - - - - concat_ws - - concat_ws ( sep text, - val1 "any" - , val2 "any" , ... ) - text - - - Concatenates all but the first argument, with separators. The first - argument is used as the separator string, and should not be NULL. - Other NULL arguments are ignored. - - - concat_ws(',', 'abcde', 2, NULL, 22) - abcde,2,22 - - - - - - - format - - format ( formatstr text - , formatarg "any" , ... ) - text - - - Formats arguments according to a format string; - see . - This function is similar to the C function sprintf. - - - format('Hello %s, %1$s', 'World') - Hello World, World - - - - - - - initcap - - initcap ( text ) - text - - - Converts the first letter of each word to upper case and the - rest to lower case. When using the libc locale - provider, words are sequences of alphanumeric characters separated - by non-alphanumeric characters; when using the ICU locale provider, - words are separated according to - Unicode Standard Annex #29. - - - initcap('hi THOMAS') - Hi Thomas - - - - - - - casefold - - casefold ( text ) - text - - - Performs case folding of the input string according to the collation. - Case folding is similar to case conversion, but the purpose of case - folding is to facilitate case-insensitive matching of strings, - whereas the purpose of case conversion is to convert to a particular - cased form. This function can only be used when the server encoding - is UTF8. - - - Ordinarily, case folding simply converts to lowercase, but there may - be exceptions depending on the collation. For instance, some - characters have more than two lowercase variants, or fold to uppercase. - - - Case folding may change the length of the string. For instance, in - the PG_UNICODE_FAST collation, Ã - (U+00DF) folds to ss. - - - casefold can be used for Unicode Default Caseless - Matching. It does not always preserve the normalized form of the - input string (see ). - - - The libc provider doesn't support case folding, so - casefold is identical to . - - - - - - - left - - left ( string text, - n integer ) - text - - - Returns first n characters in the - string, or when n is negative, returns - all but last |n| characters. - - - left('abcde', 2) - ab - - - - - - - length - - length ( text ) - integer - - - Returns the number of characters in the string. - - - length('jose') - 4 - - - - - - - md5 - - md5 ( text ) - text - - - Computes the MD5 hash of - the argument, with the result written in hexadecimal. - - - md5('abc') - 900150983cd24fb0&zwsp;d6963f7d28e17f72 - - - - - - - parse_ident - - parse_ident ( qualified_identifier text - , strict_mode boolean DEFAULT true ) - text[] - - - Splits qualified_identifier into an array of - identifiers, removing any quoting of individual identifiers. By - default, extra characters after the last identifier are considered an - error; but if the second parameter is false, then such - extra characters are ignored. (This behavior is useful for parsing - names for objects like functions.) Note that this function does not - truncate over-length identifiers. If you want truncation you can cast - the result to name[]. - - - parse_ident('"SomeSchema".someTable') - {SomeSchema,sometable} - - - - - - - pg_client_encoding - - pg_client_encoding ( ) - name - - - Returns current client encoding name. - - - pg_client_encoding() - UTF8 - - - - - - - quote_ident - - quote_ident ( text ) - text - - - Returns the given string suitably quoted to be used as an identifier - in an SQL statement string. - Quotes are added only if necessary (i.e., if the string contains - non-identifier characters or would be case-folded). - Embedded quotes are properly doubled. - See also . - - - quote_ident('Foo bar') - "Foo bar" - - - - - - - quote_literal - - quote_literal ( text ) - text - - - Returns the given string suitably quoted to be used as a string literal - in an SQL statement string. - Embedded single-quotes and backslashes are properly doubled. - Note that quote_literal returns null on null - input; if the argument might be null, - quote_nullable is often more suitable. - See also . - - - quote_literal(E'O\'Reilly') - 'O''Reilly' - - - - - - quote_literal ( anyelement ) - text - - - Converts the given value to text and then quotes it as a literal. - Embedded single-quotes and backslashes are properly doubled. - - - quote_literal(42.5) - '42.5' - - - - - - - quote_nullable - - quote_nullable ( text ) - text - - - Returns the given string suitably quoted to be used as a string literal - in an SQL statement string; or, if the argument - is null, returns NULL. - Embedded single-quotes and backslashes are properly doubled. - See also . - - - quote_nullable(NULL) - NULL - - - - - - quote_nullable ( anyelement ) - text - - - Converts the given value to text and then quotes it as a literal; - or, if the argument is null, returns NULL. - Embedded single-quotes and backslashes are properly doubled. - - - quote_nullable(42.5) - '42.5' - - - - - - - regexp_count - - regexp_count ( string text, pattern text - , start integer - , flags text ) - integer - - - Returns the number of times the POSIX regular - expression pattern matches in - the string; see - . - - - regexp_count('123456789012', '\d\d\d', 2) - 3 - - - - - - - regexp_instr - - regexp_instr ( string text, pattern text - , start integer - , N integer - , endoption integer - , flags text - , subexpr integer ) - integer - - - Returns the position within string where - the N'th match of the POSIX regular - expression pattern occurs, or zero if there is - no such match; see . - - - regexp_instr('ABCDEF', 'c(.)(..)', 1, 1, 0, 'i') - 3 - - - regexp_instr('ABCDEF', 'c(.)(..)', 1, 1, 0, 'i', 2) - 5 - - - - - - - regexp_like - - regexp_like ( string text, pattern text - , flags text ) - boolean - - - Checks whether a match of the POSIX regular - expression pattern occurs - within string; see - . - - - regexp_like('Hello World', 'world$', 'i') - t - - - - - - - regexp_match - - regexp_match ( string text, pattern text , flags text ) - text[] - - - Returns substrings within the first match of the POSIX regular - expression pattern to - the string; see - . - - - regexp_match('foobarbequebaz', '(bar)(beque)') - {bar,beque} - - - - - - - regexp_matches - - regexp_matches ( string text, pattern text , flags text ) - setof text[] - - - Returns substrings within the first match of the POSIX regular - expression pattern to - the string, or substrings within all - such matches if the g flag is used; - see . - - - regexp_matches('foobarbequebaz', 'ba.', 'g') - - - {bar} - {baz} - - - - - - - - regexp_replace - - regexp_replace ( string text, pattern text, replacement text - , flags text ) - text - - - Replaces the substring that is the first match to the POSIX - regular expression pattern, or all such - matches if the g flag is used; see - . - - - regexp_replace('Thomas', '.[mN]a.', 'M') - ThM - - - - - - regexp_replace ( string text, pattern text, replacement text, - start integer - , N integer - , flags text ) - text - - - Replaces the substring that is the N'th - match to the POSIX regular expression pattern, - or all such matches if N is zero, with the - search beginning at the start'th character - of string. If N is - omitted, it defaults to 1. See - . - - - regexp_replace('Thomas', '.', 'X', 3, 2) - ThoXas - - - regexp_replace(string=>'hello world', pattern=>'l', replacement=>'XX', start=>1, "N"=>2) - helXXo world - - - - - - - regexp_split_to_array - - regexp_split_to_array ( string text, pattern text , flags text ) - text[] - - - Splits string using a POSIX regular - expression as the delimiter, producing an array of results; see - . - - - regexp_split_to_array('hello world', '\s+') - {hello,world} - - - - - - - regexp_split_to_table - - regexp_split_to_table ( string text, pattern text , flags text ) - setof text - - - Splits string using a POSIX regular - expression as the delimiter, producing a set of results; see - . - - - regexp_split_to_table('hello world', '\s+') - - - hello - world - - - - - - - - regexp_substr - - regexp_substr ( string text, pattern text - , start integer - , N integer - , flags text - , subexpr integer ) - text - - - Returns the substring within string that - matches the N'th occurrence of the POSIX - regular expression pattern, - or NULL if there is no such match; see - . - - - regexp_substr('ABCDEF', 'c(.)(..)', 1, 1, 'i') - CDEF - - - regexp_substr('ABCDEF', 'c(.)(..)', 1, 1, 'i', 2) - EF - - - - - - - repeat - - repeat ( string text, number integer ) - text - - - Repeats string the specified - number of times. - - - repeat('Pg', 4) - PgPgPgPg - - - - - - - replace - - replace ( string text, - from text, - to text ) - text - - - Replaces all occurrences in string of - substring from with - substring to. - - - replace('abcdefabcdef', 'cd', 'XX') - abXXefabXXef - - - - - - - reverse - - reverse ( text ) - text - - - Reverses the order of the characters in the string. - - - reverse('abcde') - edcba - - - - - - - right - - right ( string text, - n integer ) - text - - - Returns last n characters in the string, - or when n is negative, returns all but - first |n| characters. - - - right('abcde', 2) - de - - - - - - - split_part - - split_part ( string text, - delimiter text, - n integer ) - text - - - Splits string at occurrences - of delimiter and returns - the n'th field (counting from one), - or when n is negative, returns - the |n|'th-from-last field. - - - split_part('abc~@~def~@~ghi', '~@~', 2) - def - - - split_part('abc,def,ghi,jkl', ',', -2) - ghi - - - - - - - starts_with - - starts_with ( string text, prefix text ) - boolean - - - Returns true if string starts - with prefix. - - - starts_with('alphabet', 'alph') - t - - - - - - - string_to_array - - string_to_array ( string text, delimiter text , null_string text ) - text[] - - - Splits the string at occurrences - of delimiter and forms the resulting fields - into a text array. - If delimiter is NULL, - each character in the string will become a - separate element in the array. - If delimiter is an empty string, then - the string is treated as a single field. - If null_string is supplied and is - not NULL, fields matching that string are - replaced by NULL. - See also array_to_string. - - - string_to_array('xx~~yy~~zz', '~~', 'yy') - {xx,NULL,zz} - - - - - - - string_to_table - - string_to_table ( string text, delimiter text , null_string text ) - setof text - - - Splits the string at occurrences - of delimiter and returns the resulting fields - as a set of text rows. - If delimiter is NULL, - each character in the string will become a - separate row of the result. - If delimiter is an empty string, then - the string is treated as a single field. - If null_string is supplied and is - not NULL, fields matching that string are - replaced by NULL. - - - string_to_table('xx~^~yy~^~zz', '~^~', 'yy') - - - xx - NULL - zz - - - - - - - - strpos - - strpos ( string text, substring text ) - integer - - - Returns first starting index of the specified substring - within string, or zero if it's not present. - (Same as position(substring in - string), but note the reversed - argument order.) - - - strpos('high', 'ig') - 2 - - - - - - - substr - - substr ( string text, start integer , count integer ) - text - - - Extracts the substring of string starting at - the start'th character, - and extending for count characters if that is - specified. (Same - as substring(string - from start - for count).) - - - substr('alphabet', 3) - phabet - - - substr('alphabet', 3, 2) - ph - - - - - - - to_ascii - - to_ascii ( string text ) - text - - - to_ascii ( string text, - encoding name ) - text - - - to_ascii ( string text, - encoding integer ) - text - - - Converts string to ASCII - from another encoding, which may be identified by name or number. - If encoding is omitted the database encoding - is assumed (which in practice is the only useful case). - The conversion consists primarily of dropping accents. - Conversion is only supported - from LATIN1, LATIN2, - LATIN9, and WIN1250 encodings. - (See the module for another, more flexible - solution.) - - - to_ascii('Karél') - Karel - - - - - - - to_bin - - to_bin ( integer ) - text - - - to_bin ( bigint ) - text - - - Converts the number to its equivalent two's complement binary - representation. - - - to_bin(2147483647) - 1111111111111111111111111111111 - - - to_bin(-1234) - 11111111111111111111101100101110 - - - - - - - to_hex - - to_hex ( integer ) - text - - - to_hex ( bigint ) - text - - - Converts the number to its equivalent two's complement hexadecimal - representation. - - - to_hex(2147483647) - 7fffffff - - - to_hex(-1234) - fffffb2e - - - - - - - to_oct - - to_oct ( integer ) - text - - - to_oct ( bigint ) - text - - - Converts the number to its equivalent two's complement octal - representation. - - - to_oct(2147483647) - 17777777777 - - - to_oct(-1234) - 37777775456 - - - - - - - translate - - translate ( string text, - from text, - to text ) - text - - - Replaces each character in string that - matches a character in the from set with the - corresponding character in the to - set. If from is longer than - to, occurrences of the extra characters in - from are deleted. - - - translate('12345', '143', 'ax') - a2x5 - - - - - - - unistr - - unistr ( text ) - text - - - Evaluate escaped Unicode characters in the argument. Unicode characters - can be specified as - \XXXX (4 hexadecimal - digits), \+XXXXXX (6 - hexadecimal digits), - \uXXXX (4 hexadecimal - digits), or \UXXXXXXXX - (8 hexadecimal digits). To specify a backslash, write two - backslashes. All other characters are taken literally. - - - - If the server encoding is not UTF-8, the Unicode code point identified - by one of these escape sequences is converted to the actual server - encoding; an error is reported if that's not possible. - - - - This function provides a (non-standard) alternative to string - constants with Unicode escapes (see ). - - - - unistr('d\0061t\+000061') - data - - - unistr('d\u0061t\U00000061') - data - - - - - -

- - - The concat, concat_ws and - format functions are variadic, so it is possible to - pass the values to be concatenated or formatted as an array marked with - the VARIADIC keyword (see ). The array's elements are - treated as if they were separate ordinary arguments to the function. - If the variadic array argument is NULL, concat - and concat_ws return NULL, but - format treats a NULL as a zero-element array. - - - - See also the aggregate function string_agg in - , and the functions for - converting between strings and the bytea type in - . - - - - <function>format</function> - - - format - - - - The function format produces output formatted according to - a format string, in a style similar to the C function - sprintf. - - - - -format(formatstr text , formatarg "any" , ... ) - - formatstr is a format string that specifies how the - result should be formatted. Text in the format string is copied - directly to the result, except where format specifiers are - used. Format specifiers act as placeholders in the string, defining how - subsequent function arguments should be formatted and inserted into the - result. Each formatarg argument is converted to text - according to the usual output rules for its data type, and then formatted - and inserted into the result string according to the format specifier(s). - - - - Format specifiers are introduced by a % character and have - the form - -%[position][flags][width]type - - where the component fields are: - - - - position (optional) - - - A string of the form n$ where - n is the index of the argument to print. - Index 1 means the first argument after - formatstr. If the position is - omitted, the default is to use the next argument in sequence. - - - - - - flags (optional) - - - Additional options controlling how the format specifier's output is - formatted. Currently the only supported flag is a minus sign - (-) which will cause the format specifier's output to be - left-justified. This has no effect unless the width - field is also specified. - - - - - - width (optional) - - - Specifies the minimum number of characters to use to - display the format specifier's output. The output is padded on the - left or right (depending on the - flag) with spaces as - needed to fill the width. A too-small width does not cause - truncation of the output, but is simply ignored. The width may be - specified using any of the following: a positive integer; an - asterisk (*) to use the next function argument as the - width; or a string of the form *n$ to - use the nth function argument as the width. - - - - If the width comes from a function argument, that argument is - consumed before the argument that is used for the format specifier's - value. If the width argument is negative, the result is left - aligned (as if the - flag had been specified) within a - field of length abs(width). - - - - - - type (required) - - - The type of format conversion to use to produce the format - specifier's output. The following types are supported: - - - - s formats the argument value as a simple - string. A null value is treated as an empty string. - - - - - I treats the argument value as an SQL - identifier, double-quoting it if necessary. - It is an error for the value to be null (equivalent to - quote_ident). - - - - - L quotes the argument value as an SQL literal. - A null value is displayed as the string NULL, without - quotes (equivalent to quote_nullable). - - - - - - - - - - - In addition to the format specifiers described above, the special sequence - %% may be used to output a literal % character. - - - - Here are some examples of the basic format conversions: - - -SELECT format('Hello %s', 'World'); -Result: Hello World - -SELECT format('Testing %s, %s, %s, %%', 'one', 'two', 'three'); -Result: Testing one, two, three, % - -SELECT format('INSERT INTO %I VALUES(%L)', 'Foo bar', E'O\'Reilly'); -Result: INSERT INTO "Foo bar" VALUES('O''Reilly') - -SELECT format('INSERT INTO %I VALUES(%L)', 'locations', 'C:\Program Files'); -Result: INSERT INTO locations VALUES('C:\Program Files') - - - - - Here are examples using width fields - and the - flag: - - -SELECT format('|%10s|', 'foo'); -Result: | foo| - -SELECT format('|%-10s|', 'foo'); -Result: |foo | - -SELECT format('|%*s|', 10, 'foo'); -Result: | foo| - -SELECT format('|%*s|', -10, 'foo'); -Result: |foo | - -SELECT format('|%-*s|', 10, 'foo'); -Result: |foo | - -SELECT format('|%-*s|', -10, 'foo'); -Result: |foo | - - - - - These examples show use of position fields: - - -SELECT format('Testing %3$s, %2$s, %1$s', 'one', 'two', 'three'); -Result: Testing three, two, one - -SELECT format('|%*2$s|', 'foo', 10, 'bar'); -Result: | bar| - -SELECT format('|%1$*2$s|', 'foo', 10, 'bar'); -Result: | foo| - - - - - Unlike the standard C function sprintf, - PostgreSQL's format function allows format - specifiers with and without position fields to be mixed - in the same format string. A format specifier without a - position field always uses the next argument after the - last argument consumed. - In addition, the format function does not require all - function arguments to be used in the format string. - For example: - - -SELECT format('Testing %3$s, %2$s, %s', 'one', 'two', 'three'); -Result: Testing three, two, three - - - - - The %I and %L format specifiers are particularly - useful for safely constructing dynamic SQL statements. See - . - - - - - - - - Binary String Functions and Operators - - - binary data - functions - - - - This section describes functions and operators for examining and - manipulating binary strings, that is values of type bytea. - Many of these are equivalent, in purpose and syntax, to the - text-string functions described in the previous section. - - - - SQL defines some string functions that use - key words, rather than commas, to separate - arguments. Details are in - . - PostgreSQL also provides versions of these functions - that use the regular function invocation syntax - (see ). - - - - <acronym>SQL</acronym> Binary String Functions and Operators - - - - - Function/Operator - - - Description - - - Example(s) - - - - - - - - - binary string - concatenation - - bytea || bytea - bytea - - - Concatenates the two binary strings. - - - '\x123456'::bytea || '\x789a00bcde'::bytea - \x123456789a00bcde - - - - - - - bit_length - - bit_length ( bytea ) - integer - - - Returns number of bits in the binary string (8 - times the octet_length). - - - bit_length('\x123456'::bytea) - 24 - - - - - - - btrim - - btrim ( bytes bytea, - bytesremoved bytea ) - bytea - - - Removes the longest string containing only bytes appearing in - bytesremoved from the start and end of - bytes. - - - btrim('\x1234567890'::bytea, '\x9012'::bytea) - \x345678 - - - - - - - ltrim - - ltrim ( bytes bytea, - bytesremoved bytea ) - bytea - - - Removes the longest string containing only bytes appearing in - bytesremoved from the start of - bytes. - - - ltrim('\x1234567890'::bytea, '\x9012'::bytea) - \x34567890 - - - - - - - octet_length - - octet_length ( bytea ) - integer - - - Returns number of bytes in the binary string. - - - octet_length('\x123456'::bytea) - 3 - - - - - - - overlay - - overlay ( bytes bytea PLACING newsubstring bytea FROM start integer FOR count integer ) - bytea - - - Replaces the substring of bytes that starts at - the start'th byte and extends - for count bytes - with newsubstring. - If count is omitted, it defaults to the length - of newsubstring. - - - overlay('\x1234567890'::bytea placing '\002\003'::bytea from 2 for 3) - \x12020390 - - - - - - - position - - position ( substring bytea IN bytes bytea ) - integer - - - Returns first starting index of the specified - substring within - bytes, or zero if it's not present. - - - position('\x5678'::bytea in '\x1234567890'::bytea) - 3 - - - - - - - rtrim - - rtrim ( bytes bytea, - bytesremoved bytea ) - bytea - - - Removes the longest string containing only bytes appearing in - bytesremoved from the end of - bytes. - - - rtrim('\x1234567890'::bytea, '\x9012'::bytea) - \x12345678 - - - - - - - substring - - substring ( bytes bytea FROM start integer FOR count integer ) - bytea - - - Extracts the substring of bytes starting at - the start'th byte if that is specified, - and stopping after count bytes if that is - specified. Provide at least one of start - and count. - - - substring('\x1234567890'::bytea from 3 for 2) - \x5678 - - - - - - - trim - - trim ( LEADING | TRAILING | BOTH - bytesremoved bytea FROM - bytes bytea ) - bytea - - - Removes the longest string containing only bytes appearing in - bytesremoved from the start, - end, or both ends (BOTH is the default) - of bytes. - - - trim('\x9012'::bytea from '\x1234567890'::bytea) - \x345678 - - - - - - trim ( LEADING | TRAILING | BOTH FROM - bytes bytea, - bytesremoved bytea ) - bytea - - - This is a non-standard syntax for trim(). - - - trim(both from '\x1234567890'::bytea, '\x9012'::bytea) - \x345678 - - - - -

- - - Additional binary string manipulation functions are available and - are listed in . Some - of them are used internally to implement the - SQL-standard string functions listed in . - - - - Other Binary String Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - bit_count - - - popcount - bit_count - - bit_count ( bytes bytea ) - bigint - - - Returns the number of bits set in the binary string (also known as - popcount). - - - bit_count('\x1234567890'::bytea) - 15 - - - - - - - crc32 - - crc32 ( bytea ) - bigint - - - Computes the CRC-32 value of the binary string. - - - crc32('abc'::bytea) - 891568578 - - - - - - - crc32c - - crc32c ( bytea ) - bigint - - - Computes the CRC-32C value of the binary string. - - - crc32c('abc'::bytea) - 910901175 - - - - - - - get_bit - - get_bit ( bytes bytea, - n bigint ) - integer - - - Extracts n'th bit - from binary string. - - - get_bit('\x1234567890'::bytea, 30) - 1 - - - - - - - get_byte - - get_byte ( bytes bytea, - n integer ) - integer - - - Extracts n'th byte - from binary string. - - - get_byte('\x1234567890'::bytea, 4) - 144 - - - - - - - length - - - binary string - length - - - length - of a binary string - binary strings, length - - length ( bytea ) - integer - - - Returns the number of bytes in the binary string. - - - length('\x1234567890'::bytea) - 5 - - - - - - length ( bytes bytea, - encoding name ) - integer - - - Returns the number of characters in the binary string, assuming - that it is text in the given encoding. - - - length('jose'::bytea, 'UTF8') - 4 - - - - - - - md5 - - md5 ( bytea ) - text - - - Computes the MD5 hash of - the binary string, with the result written in hexadecimal. - - - md5('Th\000omas'::bytea) - 8ab2d3c9689aaf18&zwsp;b4958c334c82d8b1 - - - - - - - reverse - - reverse ( bytea ) - bytea - - - Reverses the order of the bytes in the binary string. - - - reverse('\xabcd'::bytea) - \xcdab - - - - - - - set_bit - - set_bit ( bytes bytea, - n bigint, - newvalue integer ) - bytea - - - Sets n'th bit in - binary string to newvalue. - - - set_bit('\x1234567890'::bytea, 30, 0) - \x1234563890 - - - - - - - set_byte - - set_byte ( bytes bytea, - n integer, - newvalue integer ) - bytea - - - Sets n'th byte in - binary string to newvalue. - - - set_byte('\x1234567890'::bytea, 4, 64) - \x1234567840 - - - - - - - sha224 - - sha224 ( bytea ) - bytea - - - Computes the SHA-224 hash - of the binary string. - - - sha224('abc'::bytea) - \x23097d223405d8228642a477bda2&zwsp;55b32aadbce4bda0b3f7e36c9da7 - - - - - - - sha256 - - sha256 ( bytea ) - bytea - - - Computes the SHA-256 hash - of the binary string. - - - sha256('abc'::bytea) - \xba7816bf8f01cfea414140de5dae2223&zwsp;b00361a396177a9cb410ff61f20015ad - - - - - - - sha384 - - sha384 ( bytea ) - bytea - - - Computes the SHA-384 hash - of the binary string. - - - sha384('abc'::bytea) - \xcb00753f45a35e8bb5a03d699ac65007&zwsp;272c32ab0eded1631a8b605a43ff5bed&zwsp;8086072ba1e7cc2358baeca134c825a7 - - - - - - - sha512 - - sha512 ( bytea ) - bytea - - - Computes the SHA-512 hash - of the binary string. - - - sha512('abc'::bytea) - \xddaf35a193617abacc417349ae204131&zwsp;12e6fa4e89a97ea20a9eeee64b55d39a&zwsp;2192992a274fc1a836ba3c23a3feebbd&zwsp;454d4423643ce80e2a9ac94fa54ca49f - - - - - - - substr - - substr ( bytes bytea, start integer , count integer ) - bytea - - - Extracts the substring of bytes starting at - the start'th byte, - and extending for count bytes if that is - specified. (Same - as substring(bytes - from start - for count).) - - - substr('\x1234567890'::bytea, 3, 2) - \x5678 - - - - -

- - - Functions get_byte and set_byte - number the first byte of a binary string as byte 0. - Functions get_bit and set_bit - number bits from the right within each byte; for example bit 0 is the least - significant bit of the first byte, and bit 15 is the most significant bit - of the second byte. - - - - For historical reasons, the function md5 - returns a hex-encoded value of type text whereas the SHA-2 - functions return type bytea. Use the functions - encode - and decode to - convert between the two. For example write encode(sha256('abc'), - 'hex') to get a hex-encoded text representation, - or decode(md5('abc'), 'hex') to get - a bytea value. - - - - - character string - converting to binary string - - - binary string - converting to character string - - Functions for converting strings between different character sets - (encodings), and for representing arbitrary binary data in textual - form, are shown in - . For these - functions, an argument or result of type text is expressed - in the database's default encoding, while arguments or results of - type bytea are in an encoding named by another argument. - - - - Text/Binary String Conversion Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - convert - - convert ( bytes bytea, - src_encoding name, - dest_encoding name ) - bytea - - - Converts a binary string representing text in - encoding src_encoding - to a binary string in encoding dest_encoding - (see for - available conversions). - - - convert('text_in_utf8', 'UTF8', 'LATIN1') - \x746578745f696e5f75746638 - - - - - - - convert_from - - convert_from ( bytes bytea, - src_encoding name ) - text - - - Converts a binary string representing text in - encoding src_encoding - to text in the database encoding - (see for - available conversions). - - - convert_from('text_in_utf8', 'UTF8') - text_in_utf8 - - - - - - - convert_to - - convert_to ( string text, - dest_encoding name ) - bytea - - - Converts a text string (in the database encoding) to a - binary string encoded in encoding dest_encoding - (see for - available conversions). - - - convert_to('some_text', 'UTF8') - \x736f6d655f74657874 - - - - - - - encode - - encode ( bytes bytea, - format text ) - text - - - Encodes binary data into a textual representation; supported - format values are: - base64, - escape, - hex. - - - encode('123\000\001', 'base64') - MTIzAAE= - - - - - - - decode - - decode ( string text, - format text ) - bytea - - - Decodes binary data from a textual representation; supported - format values are the same as - for encode. - - - decode('MTIzAAE=', 'base64') - \x3132330001 - - - - -

- - - The encode and decode - functions support the following textual formats: - - - - base64 - - base64 format - - - - The base64 format is that - of RFC - 2045 Section 6.8. As per the RFC, encoded lines are - broken at 76 characters. However instead of the MIME CRLF - end-of-line marker, only a newline is used for end-of-line. - The decode function ignores carriage-return, - newline, space, and tab characters. Otherwise, an error is - raised when decode is supplied invalid - base64 data — including when trailing padding is incorrect. - - - - - - escape - - escape format - - - - The escape format converts zero bytes and - bytes with the high bit set into octal escape sequences - (\nnn), and it doubles - backslashes. Other byte values are represented literally. - The decode function will raise an error if a - backslash is not followed by either a second backslash or three - octal digits; it accepts other byte values unchanged. - - - - - - hex - - hex format - - - - The hex format represents each 4 bits of - data as one hexadecimal digit, 0 - through f, writing the higher-order digit of - each byte first. The encode function outputs - the a-f hex digits in lower - case. Because the smallest unit of data is 8 bits, there are - always an even number of characters returned - by encode. - The decode function - accepts the a-f characters in - either upper or lower case. An error is raised - when decode is given invalid hex data - — including when given an odd number of characters. - - - - - - - - In addition, it is possible to cast integral values to and from type - bytea. Casting an integer to bytea produces - 2, 4, or 8 bytes, depending on the width of the integer type. The result - is the two's complement representation of the integer, with the most - significant byte first. Some examples: - -1234::smallint::bytea \x04d2 -cast(1234 as bytea) \x000004d2 -cast(-1234 as bytea) \xfffffb2e -'\x8000'::bytea::smallint -32768 -'\x8000'::bytea::integer 32768 - - Casting a bytea to an integer will raise an error if the - length of the bytea exceeds the width of the integer type. - - - - See also the aggregate function string_agg in - and the large object functions - in . - - - - - - Bit String Functions and Operators - - - bit strings - functions - - - - This section describes functions and operators for examining and - manipulating bit strings, that is values of the types - bit and bit varying. (While only - type bit is mentioned in these tables, values of - type bit varying can be used interchangeably.) - Bit strings support the usual comparison operators shown in - , as well as the - operators shown in . - - - - Bit String Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - bit || bit - bit - - - Concatenation - - - B'10001' || B'011' - 10001011 - - - - - - bit & bit - bit - - - Bitwise AND (inputs must be of equal length) - - - B'10001' & B'01101' - 00001 - - - - - - bit | bit - bit - - - Bitwise OR (inputs must be of equal length) - - - B'10001' | B'01101' - 11101 - - - - - - bit # bit - bit - - - Bitwise exclusive OR (inputs must be of equal length) - - - B'10001' # B'01101' - 11100 - - - - - - ~ bit - bit - - - Bitwise NOT - - - ~ B'10001' - 01110 - - - - - - bit << integer - bit - - - Bitwise shift left - (string length is preserved) - - - B'10001' << 3 - 01000 - - - - - - bit >> integer - bit - - - Bitwise shift right - (string length is preserved) - - - B'10001' >> 2 - 00100 - - - - -

- - - Some of the functions available for binary strings are also available - for bit strings, as shown in . - - - - Bit String Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - bit_count - - bit_count ( bit ) - bigint - - - Returns the number of bits set in the bit string (also known as - popcount). - - - bit_count(B'10111') - 4 - - - - - - - bit_length - - bit_length ( bit ) - integer - - - Returns number of bits in the bit string. - - - bit_length(B'10111') - 5 - - - - - - - length - - - bit string - length - - length ( bit ) - integer - - - Returns number of bits in the bit string. - - - length(B'10111') - 5 - - - - - - - octet_length - - octet_length ( bit ) - integer - - - Returns number of bytes in the bit string. - - - octet_length(B'1011111011') - 2 - - - - - - - overlay - - overlay ( bits bit PLACING newsubstring bit FROM start integer FOR count integer ) - bit - - - Replaces the substring of bits that starts at - the start'th bit and extends - for count bits - with newsubstring. - If count is omitted, it defaults to the length - of newsubstring. - - - overlay(B'01010101010101010' placing B'11111' from 2 for 3) - 0111110101010101010 - - - - - - - position - - position ( substring bit IN bits bit ) - integer - - - Returns first starting index of the specified substring - within bits, or zero if it's not present. - - - position(B'010' in B'000001101011') - 8 - - - - - - - substring - - substring ( bits bit FROM start integer FOR count integer ) - bit - - - Extracts the substring of bits starting at - the start'th bit if that is specified, - and stopping after count bits if that is - specified. Provide at least one of start - and count. - - - substring(B'110010111111' from 3 for 2) - 00 - - - - - - - get_bit - - get_bit ( bits bit, - n integer ) - integer - - - Extracts n'th bit - from bit string; the first (leftmost) bit is bit 0. - - - get_bit(B'101010101010101010', 6) - 1 - - - - - - - set_bit - - set_bit ( bits bit, - n integer, - newvalue integer ) - bit - - - Sets n'th bit in - bit string to newvalue; - the first (leftmost) bit is bit 0. - - - set_bit(B'101010101010101010', 6, 0) - 101010001010101010 - - - - -

- - - In addition, it is possible to cast integral values to and from type - bit. - Casting an integer to bit(n) copies the rightmost - n bits. Casting an integer to a bit string width wider - than the integer itself will sign-extend on the left. - Some examples: - -44::bit(10) 0000101100 -44::bit(3) 100 -cast(-44 as bit(12)) 111111010100 -'1110'::bit(4)::integer 14 - - Note that casting to just bit means casting to - bit(1), and so will deliver only the least significant - bit of the integer. - - - - - - Pattern Matching - - - pattern matching - - - - There are three separate approaches to pattern matching provided - by PostgreSQL: the traditional - SQL LIKE operator, the - more recent SIMILAR TO operator (added in - SQL:1999), and POSIX-style regular - expressions. Aside from the basic does this string match - this pattern? operators, functions are available to extract - or replace matching substrings and to split a string at matching - locations. - - - - - If you have pattern matching needs that go beyond this, - consider writing a user-defined function in Perl or Tcl. - - - - - - While most regular-expression searches can be executed very quickly, - regular expressions can be contrived that take arbitrary amounts of - time and memory to process. Be wary of accepting regular-expression - search patterns from hostile sources. If you must do so, it is - advisable to impose a statement timeout. - - - - Searches using SIMILAR TO patterns have the same - security hazards, since SIMILAR TO provides many - of the same capabilities as POSIX-style regular - expressions. - - - - LIKE searches, being much simpler than the other - two options, are safer to use with possibly-hostile pattern sources. - - - - - SIMILAR TO and POSIX-style regular - expressions do not support nondeterministic collations. If required, use - LIKE or apply a different collation to the expression - to work around this limitation. - - - - <function>LIKE</function> - - - LIKE - - - -string LIKE pattern ESCAPE escape-character -string NOT LIKE pattern ESCAPE escape-character - - - - The LIKE expression returns true if the - string matches the supplied - pattern. (As - expected, the NOT LIKE expression returns - false if LIKE returns true, and vice versa. - An equivalent expression is - NOT (string LIKE - pattern).) - - - - If pattern does not contain percent - signs or underscores, then the pattern only represents the string - itself; in that case LIKE acts like the - equals operator. An underscore (_) in - pattern stands for (matches) any single - character; a percent sign (%) matches any sequence - of zero or more characters. - - - - Some examples: - -'abc' LIKE 'abc' true -'abc' LIKE 'a%' true -'abc' LIKE '_b_' true -'abc' LIKE 'c' false - - - - - LIKE pattern matching supports nondeterministic - collations (see ), such as - case-insensitive collations or collations that, say, ignore punctuation. - So with a case-insensitive collation, one could have: - -'AbC' LIKE 'abc' COLLATE case_insensitive true -'AbC' LIKE 'a%' COLLATE case_insensitive true - - With collations that ignore certain characters or in general that consider - strings of different lengths equal, the semantics can become a bit more - complicated. Consider these examples: - -'.foo.' LIKE 'foo' COLLATE ign_punct true -'.foo.' LIKE 'f_o' COLLATE ign_punct true -'.foo.' LIKE '_oo' COLLATE ign_punct false - - The way the matching works is that the pattern is partitioned into - sequences of wildcards and non-wildcard strings (wildcards being - _ and %). For example, the pattern - f_o is partitioned into f, _, o, the - pattern _oo is partitioned into _, - oo. The input string matches the pattern if it can be - partitioned in such a way that the wildcards match one character or any - number of characters respectively and the non-wildcard partitions are - equal under the applicable collation. So for example, '.foo.' - LIKE 'f_o' COLLATE ign_punct is true because one can partition - .foo. into .f, o, o., and then - '.f' = 'f' COLLATE ign_punct, 'o' - matches the _ wildcard, and 'o.' = 'o' COLLATE - ign_punct. But '.foo.' LIKE '_oo' COLLATE - ign_punct is false because .foo. cannot be - partitioned in a way that the first character is any character and the - rest of the string compares equal to oo. (Note that - the single-character wildcard always matches exactly one character, - independent of the collation. So in this example, the - _ would match ., but then the rest - of the input string won't match the rest of the pattern.) - - - - LIKE pattern matching always covers the entire - string. Therefore, if it's desired to match a sequence anywhere within - a string, the pattern must start and end with a percent sign. - - - - To match a literal underscore or percent sign without matching - other characters, the respective character in - pattern must be - preceded by the escape character. The default escape - character is the backslash but a different one can be selected by - using the ESCAPE clause. To match the escape - character itself, write two escape characters. - - - - - If you have turned off, - any backslashes you write in literal string constants will need to be - doubled. See for more information. - - - - - It's also possible to select no escape character by writing - ESCAPE ''. This effectively disables the - escape mechanism, which makes it impossible to turn off the - special meaning of underscore and percent signs in the pattern. - - - - According to the SQL standard, omitting ESCAPE - means there is no escape character (rather than defaulting to a - backslash), and a zero-length ESCAPE value is - disallowed. PostgreSQL's behavior in - this regard is therefore slightly nonstandard. - - - - The key word ILIKE can be used instead of - LIKE to make the match case-insensitive according to the - active locale. (But this does not support nondeterministic collations.) - This is not in the SQL standard but is a - PostgreSQL extension. - - - - The operator ~~ is equivalent to - LIKE, and ~~* corresponds to - ILIKE. There are also - !~~ and !~~* operators that - represent NOT LIKE and NOT - ILIKE, respectively. All of these operators are - PostgreSQL-specific. You may see these - operator names in EXPLAIN output and similar - places, since the parser actually translates LIKE - et al. to these operators. - - - - The phrases LIKE, ILIKE, - NOT LIKE, and NOT ILIKE are - generally treated as operators - in PostgreSQL syntax; for example they can - be used in expression - operator ANY - (subquery) constructs, although - an ESCAPE clause cannot be included there. In some - obscure cases it may be necessary to use the underlying operator names - instead. - - - - Also see the starts-with operator ^@ and the - corresponding starts_with() function, which are - useful in cases where simply matching the beginning of a string is - needed. - - - - - - <function>SIMILAR TO</function> Regular Expressions - - - regular expression - - - - - SIMILAR TO - - - substring - - - -string SIMILAR TO pattern ESCAPE escape-character -string NOT SIMILAR TO pattern ESCAPE escape-character - - - - The SIMILAR TO operator returns true or - false depending on whether its pattern matches the given string. - It is similar to LIKE, except that it - interprets the pattern using the SQL standard's definition of a - regular expression. SQL regular expressions are a curious cross - between LIKE notation and common (POSIX) regular - expression notation. - - - - Like LIKE, the SIMILAR TO - operator succeeds only if its pattern matches the entire string; - this is unlike common regular expression behavior where the pattern - can match any part of the string. - Also like - LIKE, SIMILAR TO uses - _ and % as wildcard characters denoting - any single character and any string, respectively (these are - comparable to . and .* in POSIX regular - expressions). - - - - In addition to these facilities borrowed from LIKE, - SIMILAR TO supports these pattern-matching - metacharacters borrowed from POSIX regular expressions: - - - - - | denotes alternation (either of two alternatives). - - - - - * denotes repetition of the previous item zero - or more times. - - - - - + denotes repetition of the previous item one - or more times. - - - - - ? denotes repetition of the previous item zero - or one time. - - - - - {m} denotes repetition - of the previous item exactly m times. - - - - - {m,} denotes repetition - of the previous item m or more times. - - - - - {m,n} - denotes repetition of the previous item at least m and - not more than n times. - - - - - Parentheses () can be used to group items into - a single logical item. - - - - - A bracket expression [...] specifies a character - class, just as in POSIX regular expressions. - - - - - Notice that the period (.) is not a metacharacter - for SIMILAR TO. - - - - As with LIKE, a backslash disables the special - meaning of any of these metacharacters. A different escape character - can be specified with ESCAPE, or the escape - capability can be disabled by writing ESCAPE ''. - - - - According to the SQL standard, omitting ESCAPE - means there is no escape character (rather than defaulting to a - backslash), and a zero-length ESCAPE value is - disallowed. PostgreSQL's behavior in - this regard is therefore slightly nonstandard. - - - - Another nonstandard extension is that following the escape character - with a letter or digit provides access to the escape sequences - defined for POSIX regular expressions; see - , - , and - below. - - - - Some examples: - -'abc' SIMILAR TO 'abc' true -'abc' SIMILAR TO 'a' false -'abc' SIMILAR TO '%(b|d)%' true -'abc' SIMILAR TO '(b|c)%' false -'-abc-' SIMILAR TO '%\mabc\M%' true -'xabcy' SIMILAR TO '%\mabc\M%' false - - - - - The substring function with three parameters - provides extraction of a substring that matches an SQL - regular expression pattern. The function can be written according - to standard SQL syntax: - -substring(string similar pattern escape escape-character) - - or using the now obsolete SQL:1999 syntax: - -substring(string from pattern for escape-character) - - or as a plain three-argument function: - -substring(string, pattern, escape-character) - - As with SIMILAR TO, the - specified pattern must match the entire data string, or else the - function fails and returns null. To indicate the part of the - pattern for which the matching data sub-string is of interest, - the pattern should contain - two occurrences of the escape character followed by a double quote - ("). - The text matching the portion of the pattern - between these separators is returned when the match is successful. - - - - The escape-double-quote separators actually - divide substring's pattern into three independent - regular expressions; for example, a vertical bar (|) - in any of the three sections affects only that section. Also, the first - and third of these regular expressions are defined to match the smallest - possible amount of text, not the largest, when there is any ambiguity - about how much of the data string matches which pattern. (In POSIX - parlance, the first and third regular expressions are forced to be - non-greedy.) - - - - As an extension to the SQL standard, PostgreSQL - allows there to be just one escape-double-quote separator, in which case - the third regular expression is taken as empty; or no separators, in which - case the first and third regular expressions are taken as empty. - - - - Some examples, with #" delimiting the return string: - -substring('foobar' similar '%#"o_b#"%' escape '#') oob -substring('foobar' similar '#"o_b#"%' escape '#') NULL - - - - - - <acronym>POSIX</acronym> Regular Expressions - - - regular expression - pattern matching - - - substring - - - regexp_count - - - regexp_instr - - - regexp_like - - - regexp_match - - - regexp_matches - - - regexp_replace - - - regexp_split_to_table - - - regexp_split_to_array - - - regexp_substr - - - - lists the available - operators for pattern matching using POSIX regular expressions. - - - - Regular Expression Match Operators - - - - - - Operator - - - Description - - - Example(s) - - - - - - - - text ~ text - boolean - - - String matches regular expression, case sensitively - - - 'thomas' ~ 't.*ma' - t - - - - - - text ~* text - boolean - - - String matches regular expression, case-insensitively - - - 'thomas' ~* 'T.*ma' - t - - - - - - text !~ text - boolean - - - String does not match regular expression, case sensitively - - - 'thomas' !~ 't.*max' - t - - - - - - text !~* text - boolean - - - String does not match regular expression, case-insensitively - - - 'thomas' !~* 'T.*ma' - f - - - - -

- - - POSIX regular expressions provide a more - powerful means for pattern matching than the LIKE and - SIMILAR TO operators. - Many Unix tools such as egrep, - sed, or awk use a pattern - matching language that is similar to the one described here. - - - - A regular expression is a character sequence that is an - abbreviated definition of a set of strings (a regular - set). A string is said to match a regular expression - if it is a member of the regular set described by the regular - expression. As with LIKE, pattern characters - match string characters exactly unless they are special characters - in the regular expression language — but regular expressions use - different special characters than LIKE does. - Unlike LIKE patterns, a - regular expression is allowed to match anywhere within a string, unless - the regular expression is explicitly anchored to the beginning or - end of the string. - - - - Some examples: - -'abcd' ~ 'bc' true -'abcd' ~ 'a.c' true — dot matches any character -'abcd' ~ 'a.*d' true — * repeats the preceding pattern item -'abcd' ~ '(b|x)' true — | means OR, parentheses group -'abcd' ~ '^a' true — ^ anchors to start of string -'abcd' ~ '^(b|c)' false — would match except for anchoring - - - - - The POSIX pattern language is described in much - greater detail below. - - - - The substring function with two parameters, - substring(string from - pattern), provides extraction of a - substring - that matches a POSIX regular expression pattern. It returns null if - there is no match, otherwise the first portion of the text that matched the - pattern. But if the pattern contains any parentheses, the portion - of the text that matched the first parenthesized subexpression (the - one whose left parenthesis comes first) is - returned. You can put parentheses around the whole expression - if you want to use parentheses within it without triggering this - exception. If you need parentheses in the pattern before the - subexpression you want to extract, see the non-capturing parentheses - described below. - - - - Some examples: - -substring('foobar' from 'o.b') oob -substring('foobar' from 'o(.)b') o - - - - - The regexp_count function counts the number of - places where a POSIX regular expression pattern matches a string. - It has the syntax - regexp_count(string, - pattern - , start - , flags - ). - pattern is searched for - in string, normally from the beginning of - the string, but if the start parameter is - provided then beginning from that character index. - The flags parameter is an optional text - string containing zero or more single-letter flags that change the - function's behavior. For example, including i in - flags specifies case-insensitive matching. - Supported flags are described in - . - - - - Some examples: - -regexp_count('ABCABCAXYaxy', 'A.') 3 -regexp_count('ABCABCAXYaxy', 'A.', 1, 'i') 4 - - - - - The regexp_instr function returns the starting or - ending position of the N'th match of a - POSIX regular expression pattern to a string, or zero if there is no - such match. It has the syntax - regexp_instr(string, - pattern - , start - , N - , endoption - , flags - , subexpr - ). - pattern is searched for - in string, normally from the beginning of - the string, but if the start parameter is - provided then beginning from that character index. - If N is specified - then the N'th match of the pattern - is located, otherwise the first match is located. - If the endoption parameter is omitted or - specified as zero, the function returns the position of the first - character of the match. Otherwise, endoption - must be one, and the function returns the position of the character - following the match. - The flags parameter is an optional text - string containing zero or more single-letter flags that change the - function's behavior. Supported flags are described - in . - For a pattern containing parenthesized - subexpressions, subexpr is an integer - indicating which subexpression is of interest: the result identifies - the position of the substring matching that subexpression. - Subexpressions are numbered in the order of their leading parentheses. - When subexpr is omitted or zero, the result - identifies the position of the whole match regardless of - parenthesized subexpressions. - - - - Some examples: - -regexp_instr('number of your street, town zip, FR', '[^,]+', 1, 2) - 23 -regexp_instr(string=>'ABCDEFGHI', pattern=>'(c..)(...)', start=>1, "N"=>1, endoption=>0, flags=>'i', subexpr=>2) - 6 - - - - - The regexp_like function checks whether a match - of a POSIX regular expression pattern occurs within a string, - returning boolean true or false. It has the syntax - regexp_like(string, - pattern - , flags ). - The flags parameter is an optional text - string containing zero or more single-letter flags that change the - function's behavior. Supported flags are described - in . - This function has the same results as the ~ - operator if no flags are specified. If only the i - flag is specified, it has the same results as - the ~* operator. - - - - Some examples: - -regexp_like('Hello World', 'world') false -regexp_like('Hello World', 'world', 'i') true - - - - - The regexp_match function returns a text array of - matching substring(s) within the first match of a POSIX - regular expression pattern to a string. It has the syntax - regexp_match(string, - pattern , flags ). - If there is no match, the result is NULL. - If a match is found, and the pattern contains no - parenthesized subexpressions, then the result is a single-element text - array containing the substring matching the whole pattern. - If a match is found, and the pattern contains - parenthesized subexpressions, then the result is a text array - whose n'th element is the substring matching - the n'th parenthesized subexpression of - the pattern (not counting non-capturing - parentheses; see below for details). - The flags parameter is an optional text string - containing zero or more single-letter flags that change the function's - behavior. Supported flags are described - in . - - - - Some examples: - -SELECT regexp_match('foobarbequebaz', 'bar.*que'); - regexp_match --------------- - {barbeque} -(1 row) - -SELECT regexp_match('foobarbequebaz', '(bar)(beque)'); - regexp_match --------------- - {bar,beque} -(1 row) - - - - - - In the common case where you just want the whole matching substring - or NULL for no match, the best solution is to - use regexp_substr(). - However, regexp_substr() only exists - in PostgreSQL version 15 and up. When - working in older versions, you can extract the first element - of regexp_match()'s result, for example: - -SELECT (regexp_match('foobarbequebaz', 'bar.*que'))[1]; - regexp_match --------------- - barbeque -(1 row) - - - - - - The regexp_matches function returns a set of text arrays - of matching substring(s) within matches of a POSIX regular - expression pattern to a string. It has the same syntax as - regexp_match. - This function returns no rows if there is no match, one row if there is - a match and the g flag is not given, or N - rows if there are N matches and the g flag - is given. Each returned row is a text array containing the whole - matched substring or the substrings matching parenthesized - subexpressions of the pattern, just as described above - for regexp_match. - regexp_matches accepts all the flags shown - in , plus - the g flag which commands it to return all matches, not - just the first one. - - - - Some examples: - -SELECT regexp_matches('foo', 'not there'); - regexp_matches ----------------- -(0 rows) - -SELECT regexp_matches('foobarbequebazilbarfbonk', '(b[^b]+)(b[^b]+)', 'g'); - regexp_matches ----------------- - {bar,beque} - {bazil,barf} -(2 rows) - - - - - - In most cases regexp_matches() should be used with - the g flag, since if you only want the first match, it's - easier and more efficient to use regexp_match(). - However, regexp_match() only exists - in PostgreSQL version 10 and up. When working in older - versions, a common trick is to place a regexp_matches() - call in a sub-select, for example: - -SELECT col1, (SELECT regexp_matches(col2, '(bar)(beque)')) FROM tab; - - This produces a text array if there's a match, or NULL if - not, the same as regexp_match() would do. Without the - sub-select, this query would produce no output at all for table rows - without a match, which is typically not the desired behavior. - - - - - The regexp_replace function provides substitution of - new text for substrings that match POSIX regular expression patterns. - It has the syntax - regexp_replace(string, - pattern, replacement - , flags ) - or - regexp_replace(string, - pattern, replacement, - start - , N - , flags ). - The source string is returned unchanged if - there is no match to the pattern. If there is a - match, the string is returned with the - replacement string substituted for the matching - substring. The replacement string can contain - \n, where n is 1 - through 9, to indicate that the source substring matching the - n'th parenthesized subexpression of the pattern should be - inserted, and it can contain \& to indicate that the - substring matching the entire pattern should be inserted. Write - \\ if you need to put a literal backslash in the replacement - text. - pattern is searched for - in string, normally from the beginning of - the string, but if the start parameter is - provided then beginning from that character index. - By default, only the first match of the pattern is replaced. - If N is specified and is greater than zero, - then the N'th match of the pattern - is replaced. - If the g flag is given, or - if N is specified and is zero, then all - matches at or after the start position are - replaced. (The g flag is ignored - when N is specified.) - The flags parameter is an optional text - string containing zero or more single-letter flags that change the - function's behavior. Supported flags (though - not g) are - described in . - - - - Some examples: - -regexp_replace('foobarbaz', 'b..', 'X') - fooXbaz -regexp_replace('foobarbaz', 'b..', 'X', 'g') - fooXX -regexp_replace('foobarbaz', 'b(..)', 'X\1Y', 'g') - fooXarYXazY -regexp_replace('A PostgreSQL function', 'a|e|i|o|u', 'X', 1, 0, 'i') - X PXstgrXSQL fXnctXXn -regexp_replace(string=>'A PostgreSQL function', pattern=>'a|e|i|o|u', replacement=>'X', start=>1, "N"=>3, flags=>'i') - A PostgrXSQL function - - - - - The regexp_split_to_table function splits a string using a POSIX - regular expression pattern as a delimiter. It has the syntax - regexp_split_to_table(string, pattern - , flags ). - If there is no match to the pattern, the function returns the - string. If there is at least one match, for each match it returns - the text from the end of the last match (or the beginning of the string) - to the beginning of the match. When there are no more matches, it - returns the text from the end of the last match to the end of the string. - The flags parameter is an optional text string containing - zero or more single-letter flags that change the function's behavior. - regexp_split_to_table supports the flags described in - . - - - - The regexp_split_to_array function behaves the same as - regexp_split_to_table, except that regexp_split_to_array - returns its result as an array of text. It has the syntax - regexp_split_to_array(string, pattern - , flags ). - The parameters are the same as for regexp_split_to_table. - - - - Some examples: - -SELECT foo FROM regexp_split_to_table('the quick brown fox jumps over the lazy dog', '\s+') AS foo; - foo -------- - the - quick - brown - fox - jumps - over - the - lazy - dog -(9 rows) - -SELECT regexp_split_to_array('the quick brown fox jumps over the lazy dog', '\s+'); - regexp_split_to_array ------------------------------------------------ - {the,quick,brown,fox,jumps,over,the,lazy,dog} -(1 row) - -SELECT foo FROM regexp_split_to_table('the quick brown fox', '\s*') AS foo; - foo ------ - t - h - e - q - u - i - c - k - b - r - o - w - n - f - o - x -(16 rows) - - - - - As the last example demonstrates, the regexp split functions ignore - zero-length matches that occur at the start or end of the string - or immediately after a previous match. This is contrary to the strict - definition of regexp matching that is implemented by - the other regexp functions, but is usually the most convenient behavior - in practice. Other software systems such as Perl use similar definitions. - - - - The regexp_substr function returns the substring - that matches a POSIX regular expression pattern, - or NULL if there is no match. It has the syntax - regexp_substr(string, - pattern - , start - , N - , flags - , subexpr - ). - pattern is searched for - in string, normally from the beginning of - the string, but if the start parameter is - provided then beginning from that character index. - If N is specified - then the N'th match of the pattern - is returned, otherwise the first match is returned. - The flags parameter is an optional text - string containing zero or more single-letter flags that change the - function's behavior. Supported flags are described - in . - For a pattern containing parenthesized - subexpressions, subexpr is an integer - indicating which subexpression is of interest: the result is the - substring matching that subexpression. - Subexpressions are numbered in the order of their leading parentheses. - When subexpr is omitted or zero, the result - is the whole match regardless of parenthesized subexpressions. - - - - Some examples: - -regexp_substr('number of your street, town zip, FR', '[^,]+', 1, 2) - town zip -regexp_substr('ABCDEFGHI', '(c..)(...)', 1, 1, 'i', 2) - FGH - - - - - - - Regular Expression Details - - - PostgreSQL's regular expressions are implemented - using a software package written by Henry Spencer. Much of - the description of regular expressions below is copied verbatim from his - manual. - - - - Regular expressions (REs), as defined in - POSIX 1003.2, come in two forms: - extended REs or EREs - (roughly those of egrep), and - basic REs or BREs - (roughly those of ed). - PostgreSQL supports both forms, and - also implements some extensions - that are not in the POSIX standard, but have become widely used - due to their availability in programming languages such as Perl and Tcl. - REs using these non-POSIX extensions are called - advanced REs or AREs - in this documentation. AREs are almost an exact superset of EREs, - but BREs have several notational incompatibilities (as well as being - much more limited). - We first describe the ARE and ERE forms, noting features that apply - only to AREs, and then describe how BREs differ. - - - - - PostgreSQL always initially presumes that a regular - expression follows the ARE rules. However, the more limited ERE or - BRE rules can be chosen by prepending an embedded option - to the RE pattern, as described in . - This can be useful for compatibility with applications that expect - exactly the POSIX 1003.2 rules. - - - - - A regular expression is defined as one or more - branches, separated by - |. It matches anything that matches one of the - branches. - - - - A branch is zero or more quantified atoms or - constraints, concatenated. - It matches a match for the first, followed by a match for the second, etc.; - an empty branch matches the empty string. - - - - A quantified atom is an atom possibly followed - by a single quantifier. - Without a quantifier, it matches a match for the atom. - With a quantifier, it can match some number of matches of the atom. - An atom can be any of the possibilities - shown in . - The possible quantifiers and their meanings are shown in - . - - - - A constraint matches an empty string, but matches only when - specific conditions are met. A constraint can be used where an atom - could be used, except it cannot be followed by a quantifier. - The simple constraints are shown in - ; - some more constraints are described later. - - - - - Regular Expression Atoms - - - - - Atom - Description - - - - - - (re) - (where re is any regular expression) - matches a match for - re, with the match noted for possible reporting - - - - (?:re) - as above, but the match is not noted for reporting - (a non-capturing set of parentheses) - (AREs only) - - - - . - matches any single character - - - - [chars] - a bracket expression, - matching any one of the chars (see - for more detail) - - - - \k - (where k is a non-alphanumeric character) - matches that character taken as an ordinary character, - e.g., \\ matches a backslash character - - - - \c - where c is alphanumeric - (possibly followed by other characters) - is an escape, see - (AREs only; in EREs and BREs, this matches c) - - - - { - when followed by a character other than a digit, - matches the left-brace character {; - when followed by a digit, it is the beginning of a - bound (see below) - - - - x - where x is a single character with no other - significance, matches that character - - - -

- - - An RE cannot end with a backslash (\). - - - - - If you have turned off, - any backslashes you write in literal string constants will need to be - doubled. See for more information. - - - - - Regular Expression Quantifiers - - - - - Quantifier - Matches - - - - - - * - a sequence of 0 or more matches of the atom - - - - + - a sequence of 1 or more matches of the atom - - - - ? - a sequence of 0 or 1 matches of the atom - - - - {m} - a sequence of exactly m matches of the atom - - - - {m,} - a sequence of m or more matches of the atom - - - - - {m,n} - a sequence of m through n - (inclusive) matches of the atom; m cannot exceed - n - - - - *? - non-greedy version of * - - - - +? - non-greedy version of + - - - - ?? - non-greedy version of ? - - - - {m}? - non-greedy version of {m} - - - - {m,}? - non-greedy version of {m,} - - - - - {m,n}? - non-greedy version of {m,n} - - - -

- - - The forms using {...} - are known as bounds. - The numbers m and n within a bound are - unsigned decimal integers with permissible values from 0 to 255 inclusive. - - - - Non-greedy quantifiers (available in AREs only) match the - same possibilities as their corresponding normal (greedy) - counterparts, but prefer the smallest number rather than the largest - number of matches. - See for more detail. - - - - - A quantifier cannot immediately follow another quantifier, e.g., - ** is invalid. - A quantifier cannot - begin an expression or subexpression or follow - ^ or |. - - - - - Regular Expression Constraints - - - - - Constraint - Description - - - - - - ^ - matches at the beginning of the string - - - - $ - matches at the end of the string - - - - (?=re) - positive lookahead matches at any point - where a substring matching re begins - (AREs only) - - - - (?!re) - negative lookahead matches at any point - where no substring matching re begins - (AREs only) - - - - (?<=re) - positive lookbehind matches at any point - where a substring matching re ends - (AREs only) - - - - (?<!re) - negative lookbehind matches at any point - where no substring matching re ends - (AREs only) - - - -

- - - Lookahead and lookbehind constraints cannot contain back - references (see ), - and all parentheses within them are considered non-capturing. - - - - - Bracket Expressions - - - A bracket expression is a list of - characters enclosed in []. It normally matches - any single character from the list (but see below). If the list - begins with ^, it matches any single character - not from the rest of the list. - If two characters - in the list are separated by -, this is - shorthand for the full range of characters between those two - (inclusive) in the collating sequence, - e.g., [0-9] in ASCII matches - any decimal digit. It is illegal for two ranges to share an - endpoint, e.g., a-c-e. Ranges are very - collating-sequence-dependent, so portable programs should avoid - relying on them. - - - - To include a literal ] in the list, make it the - first character (after ^, if that is used). To - include a literal -, make it the first or last - character, or the second endpoint of a range. To use a literal - - as the first endpoint of a range, enclose it - in [. and .] to make it a - collating element (see below). With the exception of these characters, - some combinations using [ - (see next paragraphs), and escapes (AREs only), all other special - characters lose their special significance within a bracket expression. - In particular, \ is not special when following - ERE or BRE rules, though it is special (as introducing an escape) - in AREs. - - - - Within a bracket expression, a collating element (a character, a - multiple-character sequence that collates as if it were a single - character, or a collating-sequence name for either) enclosed in - [. and .] stands for the - sequence of characters of that collating element. The sequence is - treated as a single element of the bracket expression's list. This - allows a bracket - expression containing a multiple-character collating element to - match more than one character, e.g., if the collating sequence - includes a ch collating element, then the RE - [[.ch.]]*c matches the first five characters of - chchcc. - - - - - PostgreSQL currently does not support multi-character collating - elements. This information describes possible future behavior. - - - - - Within a bracket expression, a collating element enclosed in - [= and =] is an equivalence - class, standing for the sequences of characters of all collating - elements equivalent to that one, including itself. (If there are - no other equivalent collating elements, the treatment is as if the - enclosing delimiters were [. and - .].) For example, if o and - ^ are the members of an equivalence class, then - [[=o=]], [[=^=]], and - [o^] are all synonymous. An equivalence class - cannot be an endpoint of a range. - - - - Within a bracket expression, the name of a character class - enclosed in [: and :] stands - for the list of all characters belonging to that class. A character - class cannot be used as an endpoint of a range. - The POSIX standard defines these character class - names: - alnum (letters and numeric digits), - alpha (letters), - blank (space and tab), - cntrl (control characters), - digit (numeric digits), - graph (printable characters except space), - lower (lower-case letters), - print (printable characters including space), - punct (punctuation), - space (any white space), - upper (upper-case letters), - and xdigit (hexadecimal digits). - The behavior of these standard character classes is generally - consistent across platforms for characters in the 7-bit ASCII set. - Whether a given non-ASCII character is considered to belong to one - of these classes depends on the collation - that is used for the regular-expression function or operator - (see ), or by default on the - database's LC_CTYPE locale setting (see - ). The classification of non-ASCII - characters can vary across platforms even in similarly-named - locales. (But the C locale never considers any - non-ASCII characters to belong to any of these classes.) - In addition to these standard character - classes, PostgreSQL defines - the word character class, which is the same as - alnum plus the underscore (_) - character, and - the ascii character class, which contains exactly - the 7-bit ASCII set. - - - - There are two special cases of bracket expressions: the bracket - expressions [[:<:]] and - [[:>:]] are constraints, - matching empty strings at the beginning - and end of a word respectively. A word is defined as a sequence - of word characters that is neither preceded nor followed by word - characters. A word character is any character belonging to the - word character class, that is, any letter, digit, - or underscore. This is an extension, compatible with but not - specified by POSIX 1003.2, and should be used with - caution in software intended to be portable to other systems. - The constraint escapes described below are usually preferable; they - are no more standard, but are easier to type. - - - - - Regular Expression Escapes - - - Escapes are special sequences beginning with \ - followed by an alphanumeric character. Escapes come in several varieties: - character entry, class shorthands, constraint escapes, and back references. - A \ followed by an alphanumeric character but not constituting - a valid escape is illegal in AREs. - In EREs, there are no escapes: outside a bracket expression, - a \ followed by an alphanumeric character merely stands for - that character as an ordinary character, and inside a bracket expression, - \ is an ordinary character. - (The latter is the one actual incompatibility between EREs and AREs.) - - - - Character-entry escapes exist to make it easier to specify - non-printing and other inconvenient characters in REs. They are - shown in . - - - - Class-shorthand escapes provide shorthands for certain - commonly-used character classes. They are - shown in . - - - - A constraint escape is a constraint, - matching the empty string if specific conditions are met, - written as an escape. They are - shown in . - - - - A back reference (\n) matches the - same string matched by the previous parenthesized subexpression specified - by the number n - (see ). For example, - ([bc])\1 matches bb or cc - but not bc or cb. - The subexpression must entirely precede the back reference in the RE. - Subexpressions are numbered in the order of their leading parentheses. - Non-capturing parentheses do not define subexpressions. - The back reference considers only the string characters matched by the - referenced subexpression, not any constraints contained in it. For - example, (^\d)\1 will match 22. - - - - Regular Expression Character-Entry Escapes - - - - - Escape - Description - - - - - - \a - alert (bell) character, as in C - - - - \b - backspace, as in C - - - - \B - synonym for backslash (\) to help reduce the need for backslash - doubling - - - - \cX - (where X is any character) the character whose - low-order 5 bits are the same as those of - X, and whose other bits are all zero - - - - \e - the character whose collating-sequence name - is ESC, - or failing that, the character with octal value 033 - - - - \f - form feed, as in C - - - - \n - newline, as in C - - - - \r - carriage return, as in C - - - - \t - horizontal tab, as in C - - - - \uwxyz - (where wxyz is exactly four hexadecimal digits) - the character whose hexadecimal value is - 0xwxyz - - - - - \Ustuvwxyz - (where stuvwxyz is exactly eight hexadecimal - digits) - the character whose hexadecimal value is - 0xstuvwxyz - - - - - \v - vertical tab, as in C - - - - \xhhh - (where hhh is any sequence of hexadecimal - digits) - the character whose hexadecimal value is - 0xhhh - (a single character no matter how many hexadecimal digits are used) - - - - - \0 - the character whose value is 0 (the null byte) - - - - \xy - (where xy is exactly two octal digits, - and is not a back reference) - the character whose octal value is - 0xy - - - - \xyz - (where xyz is exactly three octal digits, - and is not a back reference) - the character whose octal value is - 0xyz - - - -

- - - Hexadecimal digits are 0-9, - a-f, and A-F. - Octal digits are 0-7. - - - - Numeric character-entry escapes specifying values outside the ASCII range - (0–127) have meanings dependent on the database encoding. When the - encoding is UTF-8, escape values are equivalent to Unicode code points, - for example \u1234 means the character U+1234. - For other multibyte encodings, character-entry escapes usually just - specify the concatenation of the byte values for the character. If the - escape value does not correspond to any legal character in the database - encoding, no error will be raised, but it will never match any data. - - - - The character-entry escapes are always taken as ordinary characters. - For example, \135 is ] in ASCII, but - \135 does not terminate a bracket expression. - - - - Regular Expression Class-Shorthand Escapes - - - - - Escape - Description - - - - - - \d - matches any digit, like - [[:digit:]] - - - - \s - matches any whitespace character, like - [[:space:]] - - - - \w - matches any word character, like - [[:word:]] - - - - \D - matches any non-digit, like - [^[:digit:]] - - - - \S - matches any non-whitespace character, like - [^[:space:]] - - - - \W - matches any non-word character, like - [^[:word:]] - - - -

- - - The class-shorthand escapes also work within bracket expressions, - although the definitions shown above are not quite syntactically - valid in that context. - For example, [a-c\d] is equivalent to - [a-c[:digit:]]. - - - - Regular Expression Constraint Escapes - - - - - Escape - Description - - - - - - \A - matches only at the beginning of the string - (see for how this differs from - ^) - - - - \m - matches only at the beginning of a word - - - - \M - matches only at the end of a word - - - - \y - matches only at the beginning or end of a word - - - - \Y - matches only at a point that is not the beginning or end of a - word - - - - \Z - matches only at the end of the string - (see for how this differs from - $) - - - -

- - - A word is defined as in the specification of - [[:<:]] and [[:>:]] above. - Constraint escapes are illegal within bracket expressions. - - - - Regular Expression Back References - - - - - Escape - Description - - - - - - \m - (where m is a nonzero digit) - a back reference to the m'th subexpression - - - - \mnn - (where m is a nonzero digit, and - nn is some more digits, and the decimal value - mnn is not greater than the number of closing capturing - parentheses seen so far) - a back reference to the mnn'th subexpression - - - -

- - - - There is an inherent ambiguity between octal character-entry - escapes and back references, which is resolved by the following heuristics, - as hinted at above. - A leading zero always indicates an octal escape. - A single non-zero digit, not followed by another digit, - is always taken as a back reference. - A multi-digit sequence not starting with a zero is taken as a back - reference if it comes after a suitable subexpression - (i.e., the number is in the legal range for a back reference), - and otherwise is taken as octal. - - - - - - Regular Expression Metasyntax - - - In addition to the main syntax described above, there are some special - forms and miscellaneous syntactic facilities available. - - - - An RE can begin with one of two special director prefixes. - If an RE begins with ***:, - the rest of the RE is taken as an ARE. (This normally has no effect in - PostgreSQL, since REs are assumed to be AREs; - but it does have an effect if ERE or BRE mode had been specified by - the flags parameter to a regex function.) - If an RE begins with ***=, - the rest of the RE is taken to be a literal string, - with all characters considered ordinary characters. - - - - An ARE can begin with embedded options: - a sequence (?xyz) - (where xyz is one or more alphabetic characters) - specifies options affecting the rest of the RE. - These options override any previously determined options — - in particular, they can override the case-sensitivity behavior implied by - a regex operator, or the flags parameter to a regex - function. - The available option letters are - shown in . - Note that these same option letters are used in the flags - parameters of regex functions. - - - - ARE Embedded-Option Letters - - - - - Option - Description - - - - - - b - rest of RE is a BRE - - - - c - case-sensitive matching (overrides operator type) - - - - e - rest of RE is an ERE - - - - i - case-insensitive matching (see - ) (overrides operator type) - - - - m - historical synonym for n - - - - n - newline-sensitive matching (see - ) - - - - p - partial newline-sensitive matching (see - ) - - - - q - rest of RE is a literal (quoted) string, all ordinary - characters - - - - s - non-newline-sensitive matching (default) - - - - t - tight syntax (default; see below) - - - - w - inverse partial newline-sensitive (weird) matching - (see ) - - - - x - expanded syntax (see below) - - - -

- - - Embedded options take effect at the ) terminating the sequence. - They can appear only at the start of an ARE (after the - ***: director if any). - - - - In addition to the usual (tight) RE syntax, in which all - characters are significant, there is an expanded syntax, - available by specifying the embedded x option. - In the expanded syntax, - white-space characters in the RE are ignored, as are - all characters between a # - and the following newline (or the end of the RE). This - permits paragraphing and commenting a complex RE. - There are three exceptions to that basic rule: - - - - - a white-space character or # preceded by \ is - retained - - - - - white space or # within a bracket expression is retained - - - - - white space and comments cannot appear within multi-character symbols, - such as (?: - - - - - For this purpose, white-space characters are blank, tab, newline, and - any character that belongs to the space character class. - - - - Finally, in an ARE, outside bracket expressions, the sequence - (?#ttt) - (where ttt is any text not containing a )) - is a comment, completely ignored. - Again, this is not allowed between the characters of - multi-character symbols, like (?:. - Such comments are more a historical artifact than a useful facility, - and their use is deprecated; use the expanded syntax instead. - - - - None of these metasyntax extensions is available if - an initial ***= director - has specified that the user's input be treated as a literal string - rather than as an RE. - - - - - Regular Expression Matching Rules - - - In the event that an RE could match more than one substring of a given - string, the RE matches the one starting earliest in the string. - If the RE could match more than one substring starting at that point, - either the longest possible match or the shortest possible match will - be taken, depending on whether the RE is greedy or - non-greedy. - - - - Whether an RE is greedy or not is determined by the following rules: - - - - Most atoms, and all constraints, have no greediness attribute (because - they cannot match variable amounts of text anyway). - - - - - Adding parentheses around an RE does not change its greediness. - - - - - A quantified atom with a fixed-repetition quantifier - ({m} - or - {m}?) - has the same greediness (possibly none) as the atom itself. - - - - - A quantified atom with other normal quantifiers (including - {m,n} - with m equal to n) - is greedy (prefers longest match). - - - - - A quantified atom with a non-greedy quantifier (including - {m,n}? - with m equal to n) - is non-greedy (prefers shortest match). - - - - - A branch — that is, an RE that has no top-level - | operator — has the same greediness as the first - quantified atom in it that has a greediness attribute. - - - - - An RE consisting of two or more branches connected by the - | operator is always greedy. - - - - - - - The above rules associate greediness attributes not only with individual - quantified atoms, but with branches and entire REs that contain quantified - atoms. What that means is that the matching is done in such a way that - the branch, or whole RE, matches the longest or shortest possible - substring as a whole. Once the length of the entire match - is determined, the part of it that matches any particular subexpression - is determined on the basis of the greediness attribute of that - subexpression, with subexpressions starting earlier in the RE taking - priority over ones starting later. - - - - An example of what this means: - -SELECT SUBSTRING('XY1234Z', 'Y*([0-9]{1,3})'); -Result: 123 -SELECT SUBSTRING('XY1234Z', 'Y*?([0-9]{1,3})'); -Result: 1 - - In the first case, the RE as a whole is greedy because Y* - is greedy. It can match beginning at the Y, and it matches - the longest possible string starting there, i.e., Y123. - The output is the parenthesized part of that, or 123. - In the second case, the RE as a whole is non-greedy because Y*? - is non-greedy. It can match beginning at the Y, and it matches - the shortest possible string starting there, i.e., Y1. - The subexpression [0-9]{1,3} is greedy but it cannot change - the decision as to the overall match length; so it is forced to match - just 1. - - - - In short, when an RE contains both greedy and non-greedy subexpressions, - the total match length is either as long as possible or as short as - possible, according to the attribute assigned to the whole RE. The - attributes assigned to the subexpressions only affect how much of that - match they are allowed to eat relative to each other. - - - - The quantifiers {1,1} and {1,1}? - can be used to force greediness or non-greediness, respectively, - on a subexpression or a whole RE. - This is useful when you need the whole RE to have a greediness attribute - different from what's deduced from its elements. As an example, - suppose that we are trying to separate a string containing some digits - into the digits and the parts before and after them. We might try to - do that like this: - -SELECT regexp_match('abc01234xyz', '(.*)(\d+)(.*)'); -Result: {abc0123,4,xyz} - - That didn't work: the first .* is greedy so - it eats as much as it can, leaving the \d+ to - match at the last possible place, the last digit. We might try to fix - that by making it non-greedy: - -SELECT regexp_match('abc01234xyz', '(.*?)(\d+)(.*)'); -Result: {abc,0,""} - - That didn't work either, because now the RE as a whole is non-greedy - and so it ends the overall match as soon as possible. We can get what - we want by forcing the RE as a whole to be greedy: - -SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}'); -Result: {abc,01234,xyz} - - Controlling the RE's overall greediness separately from its components' - greediness allows great flexibility in handling variable-length patterns. - - - - When deciding what is a longer or shorter match, - match lengths are measured in characters, not collating elements. - An empty string is considered longer than no match at all. - For example: - bb* - matches the three middle characters of abbbc; - (week|wee)(night|knights) - matches all ten characters of weeknights; - when (.*).* - is matched against abc the parenthesized subexpression - matches all three characters; and when - (a*)* is matched against bc - both the whole RE and the parenthesized - subexpression match an empty string. - - - - If case-independent matching is specified, - the effect is much as if all case distinctions had vanished from the - alphabet. - When an alphabetic that exists in multiple cases appears as an - ordinary character outside a bracket expression, it is effectively - transformed into a bracket expression containing both cases, - e.g., x becomes [xX]. - When it appears inside a bracket expression, all case counterparts - of it are added to the bracket expression, e.g., - [x] becomes [xX] - and [^x] becomes [^xX]. - - - - If newline-sensitive matching is specified, . - and bracket expressions using ^ - will never match the newline character - (so that matches will not cross lines unless the RE - explicitly includes a newline) - and ^ and $ - will match the empty string after and before a newline - respectively, in addition to matching at beginning and end of string - respectively. - But the ARE escapes \A and \Z - continue to match beginning or end of string only. - Also, the character class shorthands \D - and \W will match a newline regardless of this mode. - (Before PostgreSQL 14, they did not match - newlines when in newline-sensitive mode. - Write [^[:digit:]] - or [^[:word:]] to get the old behavior.) - - - - If partial newline-sensitive matching is specified, - this affects . and bracket expressions - as with newline-sensitive matching, but not ^ - and $. - - - - If inverse partial newline-sensitive matching is specified, - this affects ^ and $ - as with newline-sensitive matching, but not . - and bracket expressions. - This isn't very useful but is provided for symmetry. - - - - - Limits and Compatibility - - - No particular limit is imposed on the length of REs in this - implementation. However, - programs intended to be highly portable should not employ REs longer - than 256 bytes, - as a POSIX-compliant implementation can refuse to accept such REs. - - - - The only feature of AREs that is actually incompatible with - POSIX EREs is that \ does not lose its special - significance inside bracket expressions. - All other ARE features use syntax which is illegal or has - undefined or unspecified effects in POSIX EREs; - the *** syntax of directors likewise is outside the POSIX - syntax for both BREs and EREs. - - - - Many of the ARE extensions are borrowed from Perl, but some have - been changed to clean them up, and a few Perl extensions are not present. - Incompatibilities of note include \b, \B, - the lack of special treatment for a trailing newline, - the addition of complemented bracket expressions to the things - affected by newline-sensitive matching, - the restrictions on parentheses and back references in lookahead/lookbehind - constraints, and the longest/shortest-match (rather than first-match) - matching semantics. - - - - - Basic Regular Expressions - - - BREs differ from EREs in several respects. - In BREs, |, +, and ? - are ordinary characters and there is no equivalent - for their functionality. - The delimiters for bounds are - \{ and \}, - with { and } - by themselves ordinary characters. - The parentheses for nested subexpressions are - $ and $, - with ( and ) by themselves ordinary characters. - ^ is an ordinary character except at the beginning of the - RE or the beginning of a parenthesized subexpression, - $ is an ordinary character except at the end of the - RE or the end of a parenthesized subexpression, - and * is an ordinary character if it appears at the beginning - of the RE or the beginning of a parenthesized subexpression - (after a possible leading ^). - Finally, single-digit back references are available, and - \< and \> - are synonyms for - [[:<:]] and [[:>:]] - respectively; no other escapes are available in BREs. - - - - - - - Differences from SQL Standard and XQuery - - - LIKE_REGEX - - - - OCCURRENCES_REGEX - - - - POSITION_REGEX - - - - SUBSTRING_REGEX - - - - TRANSLATE_REGEX - - - - XQuery regular expressions - - - - Since SQL:2008, the SQL standard includes regular expression operators - and functions that performs pattern - matching according to the XQuery regular expression - standard: - - LIKE_REGEX - OCCURRENCES_REGEX - POSITION_REGEX - SUBSTRING_REGEX - TRANSLATE_REGEX - - PostgreSQL does not currently implement these - operators and functions. You can get approximately equivalent - functionality in each case as shown in . (Various optional clauses on - both sides have been omitted in this table.) - - - - Regular Expression Functions Equivalencies - - - - - SQL standard - PostgreSQL - - - - - - string LIKE_REGEX pattern - regexp_like(string, pattern) or string ~ pattern - - - - OCCURRENCES_REGEX(pattern IN string) - regexp_count(string, pattern) - - - - POSITION_REGEX(pattern IN string) - regexp_instr(string, pattern) - - - - SUBSTRING_REGEX(pattern IN string) - regexp_substr(string, pattern) - - - - TRANSLATE_REGEX(pattern IN string WITH replacement) - regexp_replace(string, pattern, replacement) - - - -

- - - Regular expression functions similar to those provided by PostgreSQL are - also available in a number of other SQL implementations, whereas the - SQL-standard functions are not as widely implemented. Some of the - details of the regular expression syntax will likely differ in each - implementation. - - - - The SQL-standard operators and functions use XQuery regular expressions, - which are quite close to the ARE syntax described above. - Notable differences between the existing POSIX-based - regular-expression feature and XQuery regular expressions include: - - - - - XQuery character class subtraction is not supported. An example of - this feature is using the following to match only English - consonants: [a-z-[aeiou]]. - - - - - XQuery character class shorthands \c, - \C, \i, - and \I are not supported. - - - - - XQuery character class elements - using \p{UnicodeProperty} or the - inverse \P{UnicodeProperty} are not supported. - - - - - POSIX interprets character classes such as \w - (see ) - according to the prevailing locale (which you can control by - attaching a COLLATE clause to the operator or - function). XQuery specifies these classes by reference to Unicode - character properties, so equivalent behavior is obtained only with - a locale that follows the Unicode rules. - - - - - The SQL standard (not XQuery itself) attempts to cater for more - variants of newline than POSIX does. The - newline-sensitive matching options described above consider only - ASCII NL (\n) to be a newline, but SQL would have - us treat CR (\r), CRLF (\r\n) - (a Windows-style newline), and some Unicode-only characters like - LINE SEPARATOR (U+2028) as newlines as well. - Notably, . and \s should - count \r\n as one character not two according to - SQL. - - - - - Of the character-entry escapes described in - , - XQuery supports only \n, \r, - and \t. - - - - - XQuery does not support - the [:name:] syntax - for character classes within bracket expressions. - - - - - XQuery does not have lookahead or lookbehind constraints, - nor any of the constraint escapes described in - . - - - - - The metasyntax forms described in - do not exist in XQuery. - - - - - The regular expression flag letters defined by XQuery are - related to but not the same as the option letters for POSIX - (). While the - i and q options behave the - same, others do not: - - - - XQuery's s (allow dot to match newline) - and m (allow ^ - and $ to match at newlines) flags provide - access to the same behaviors as - POSIX's n, p - and w flags, but they - do not match the behavior of - POSIX's s and m flags. - Note in particular that dot-matches-newline is the default - behavior in POSIX but not XQuery. - - - - - XQuery's x (ignore whitespace in pattern) flag - is noticeably different from POSIX's expanded-mode flag. - POSIX's x flag also - allows # to begin a comment in the pattern, - and POSIX will not ignore a whitespace character after a - backslash. - - - - - - - - - - - - - - - Data Type Formatting Functions - - - formatting - - - - The PostgreSQL formatting functions - provide a powerful set of tools for converting various data types - (date/time, integer, floating point, numeric) to formatted strings - and for converting from formatted strings to specific data types. - lists them. - These functions all follow a common calling convention: the first - argument is the value to be formatted and the second argument is a - template that defines the output or input format. - - - - Formatting Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - to_char - - to_char ( timestamp, text ) - text - - - to_char ( timestamp with time zone, text ) - text - - - Converts time stamp to string according to the given format. - - - to_char(timestamp '2002-04-20 17:31:12.66', 'HH12:MI:SS') - 05:31:12 - - - - - - to_char ( interval, text ) - text - - - Converts interval to string according to the given format. - - - to_char(interval '15h 2m 12s', 'HH24:MI:SS') - 15:02:12 - - - - - - to_char ( numeric_type, text ) - text - - - Converts number to string according to the given format; available - for integer, bigint, numeric, - real, double precision. - - - to_char(125, '999') - 125 - - - to_char(125.8::real, '999D9') - 125.8 - - - to_char(-125.8, '999D99S') - 125.80- - - - - - - - to_date - - to_date ( text, text ) - date - - - Converts string to date according to the given format. - - - to_date('05 Dec 2000', 'DD Mon YYYY') - 2000-12-05 - - - - - - - to_number - - to_number ( text, text ) - numeric - - - Converts string to numeric according to the given format. - - - to_number('12,454.8-', '99G999D9S') - -12454.8 - - - - - - - to_timestamp - - to_timestamp ( text, text ) - timestamp with time zone - - - Converts string to time stamp according to the given format. - (See also to_timestamp(double precision) in - .) - - - to_timestamp('05 Dec 2000', 'DD Mon YYYY') - 2000-12-05 00:00:00-05 - - - - -

- - - - to_timestamp and to_date - exist to handle input formats that cannot be converted by - simple casting. For most standard date/time formats, simply casting the - source string to the required data type works, and is much easier. - Similarly, to_number is unnecessary for standard numeric - representations. - - - - - In a to_char output template string, there are certain - patterns that are recognized and replaced with appropriately-formatted - data based on the given value. Any text that is not a template pattern is - simply copied verbatim. Similarly, in an input template string (for the - other functions), template patterns identify the values to be supplied by - the input data string. If there are characters in the template string - that are not template patterns, the corresponding characters in the input - data string are simply skipped over (whether or not they are equal to the - template string characters). - - - - shows the - template patterns available for formatting date and time values. - - - - Template Patterns for Date/Time Formatting - - - - Pattern - Description - - - - - HH - hour of day (01–12) - - - HH12 - hour of day (01–12) - - - HH24 - hour of day (00–23) - - - MI - minute (00–59) - - - SS - second (00–59) - - - MS - millisecond (000–999) - - - US - microsecond (000000–999999) - - - FF1 - tenth of second (0–9) - - - FF2 - hundredth of second (00–99) - - - FF3 - millisecond (000–999) - - - FF4 - tenth of a millisecond (0000–9999) - - - FF5 - hundredth of a millisecond (00000–99999) - - - FF6 - microsecond (000000–999999) - - - SSSS, SSSSS - seconds past midnight (0–86399) - - - AM, am, - PM or pm - meridiem indicator (without periods) - - - A.M., a.m., - P.M. or p.m. - meridiem indicator (with periods) - - - Y,YYY - year (4 or more digits) with comma - - - YYYY - year (4 or more digits) - - - YYY - last 3 digits of year - - - YY - last 2 digits of year - - - Y - last digit of year - - - IYYY - ISO 8601 week-numbering year (4 or more digits) - - - IYY - last 3 digits of ISO 8601 week-numbering year - - - IY - last 2 digits of ISO 8601 week-numbering year - - - I - last digit of ISO 8601 week-numbering year - - - BC, bc, - AD or ad - era indicator (without periods) - - - B.C., b.c., - A.D. or a.d. - era indicator (with periods) - - - MONTH - full upper case month name (blank-padded to 9 chars) - - - Month - full capitalized month name (blank-padded to 9 chars) - - - month - full lower case month name (blank-padded to 9 chars) - - - MON - abbreviated upper case month name (3 chars in English, localized lengths vary) - - - Mon - abbreviated capitalized month name (3 chars in English, localized lengths vary) - - - mon - abbreviated lower case month name (3 chars in English, localized lengths vary) - - - MM - month number (01–12) - - - DAY - full upper case day name (blank-padded to 9 chars) - - - Day - full capitalized day name (blank-padded to 9 chars) - - - day - full lower case day name (blank-padded to 9 chars) - - - DY - abbreviated upper case day name (3 chars in English, localized lengths vary) - - - Dy - abbreviated capitalized day name (3 chars in English, localized lengths vary) - - - dy - abbreviated lower case day name (3 chars in English, localized lengths vary) - - - DDD - day of year (001–366) - - - IDDD - day of ISO 8601 week-numbering year (001–371; day 1 of the year is Monday of the first ISO week) - - - DD - day of month (01–31) - - - D - day of the week, Sunday (1) to Saturday (7) - - - ID - ISO 8601 day of the week, Monday (1) to Sunday (7) - - - W - week of month (1–5) (the first week starts on the first day of the month) - - - WW - week number of year (1–53) (the first week starts on the first day of the year) - - - IW - week number of ISO 8601 week-numbering year (01–53; the first Thursday of the year is in week 1) - - - CC - century (2 digits) (the twenty-first century starts on 2001-01-01) - - - J - Julian Date (integer days since November 24, 4714 BC at local - midnight; see ) - - - Q - quarter - - - RM - month in upper case Roman numerals (I–XII; I=January) - - - rm - month in lower case Roman numerals (i–xii; i=January) - - - TZ - upper case time-zone abbreviation - - - tz - lower case time-zone abbreviation - - - TZH - time-zone hours - - - TZM - time-zone minutes - - - OF - time-zone offset from UTC (HH - or HH:MM) - - - -

- - - Modifiers can be applied to any template pattern to alter its - behavior. For example, FMMonth - is the Month pattern with the - FM modifier. - shows the - modifier patterns for date/time formatting. - - - - Template Pattern Modifiers for Date/Time Formatting - - - - Modifier - Description - Example - - - - - FM prefix - fill mode (suppress leading zeroes and padding blanks) - FMMonth - - - TH suffix - upper case ordinal number suffix - DDTH, e.g., 12TH - - - th suffix - lower case ordinal number suffix - DDth, e.g., 12th - - - FX prefix - fixed format global option (see usage notes) - FX Month DD Day - - - TM prefix - translation mode (use localized day and month names based on - ) - TMMonth - - - SP suffix - spell mode (not implemented) - DDSP - - - -

- - - Usage notes for date/time formatting: - - - - - FM suppresses leading zeroes and trailing blanks - that would otherwise be added to make the output of a pattern be - fixed-width. In PostgreSQL, - FM modifies only the next specification, while in - Oracle FM affects all subsequent - specifications, and repeated FM modifiers - toggle fill mode on and off. - - - - - - TM suppresses trailing blanks whether or - not FM is specified. - - - - - - to_timestamp and to_date - ignore letter case in the input; so for - example MON, Mon, - and mon all accept the same strings. When using - the TM modifier, case-folding is done according to - the rules of the function's input collation (see - ). - - - - - - to_timestamp and to_date - skip multiple blank spaces at the beginning of the input string and - around date and time values unless the FX option is used. For example, - to_timestamp(' 2000 JUN', 'YYYY MON') and - to_timestamp('2000 - JUN', 'YYYY-MON') work, but - to_timestamp('2000 JUN', 'FXYYYY MON') returns an error - because to_timestamp expects only a single space. - FX must be specified as the first item in - the template. - - - - - - A separator (a space or non-letter/non-digit character) in the template string of - to_timestamp and to_date - matches any single separator in the input string or is skipped, - unless the FX option is used. - For example, to_timestamp('2000JUN', 'YYYY///MON') and - to_timestamp('2000/JUN', 'YYYY MON') work, but - to_timestamp('2000//JUN', 'YYYY/MON') - returns an error because the number of separators in the input string - exceeds the number of separators in the template. - - - If FX is specified, a separator in the template string - matches exactly one character in the input string. But note that the - input string character is not required to be the same as the separator from the template string. - For example, to_timestamp('2000/JUN', 'FXYYYY MON') - works, but to_timestamp('2000/JUN', 'FXYYYY MON') - returns an error because the second space in the template string consumes - the letter J from the input string. - - - - - - A TZH template pattern can match a signed number. - Without the FX option, minus signs may be ambiguous, - and could be interpreted as a separator. - This ambiguity is resolved as follows: If the number of separators before - TZH in the template string is less than the number of - separators before the minus sign in the input string, the minus sign - is interpreted as part of TZH. - Otherwise, the minus sign is considered to be a separator between values. - For example, to_timestamp('2000 -10', 'YYYY TZH') matches - -10 to TZH, but - to_timestamp('2000 -10', 'YYYY TZH') - matches 10 to TZH. - - - - - - Ordinary text is allowed in to_char - templates and will be output literally. You can put a substring - in double quotes to force it to be interpreted as literal text - even if it contains template patterns. For example, in - '"Hello Year "YYYY', the YYYY - will be replaced by the year data, but the single Y in Year - will not be. - In to_date, to_number, - and to_timestamp, literal text and double-quoted - strings result in skipping the number of characters contained in the - string; for example "XX" skips two input characters - (whether or not they are XX). - - - - Prior to PostgreSQL 12, it was possible to - skip arbitrary text in the input string using non-letter or non-digit - characters. For example, - to_timestamp('2000y6m1d', 'yyyy-MM-DD') used to - work. Now you can only use letter characters for this purpose. For example, - to_timestamp('2000y6m1d', 'yyyytMMtDDt') and - to_timestamp('2000y6m1d', 'yyyy"y"MM"m"DD"d"') - skip y, m, and - d. - - - - - - - If you want to have a double quote in the output you must - precede it with a backslash, for example '\"YYYY - Month\"'. - Backslashes are not otherwise special outside of double-quoted - strings. Within a double-quoted string, a backslash causes the - next character to be taken literally, whatever it is (but this - has no special effect unless the next character is a double quote - or another backslash). - - - - - - In to_timestamp and to_date, - if the year format specification is less than four digits, e.g., - YYY, and the supplied year is less than four digits, - the year will be adjusted to be nearest to the year 2020, e.g., - 95 becomes 1995. - - - - - - In to_timestamp and to_date, - negative years are treated as signifying BC. If you write both a - negative year and an explicit BC field, you get AD - again. An input of year zero is treated as 1 BC. - - - - - - In to_timestamp and to_date, - the YYYY conversion has a restriction when - processing years with more than 4 digits. You must - use some non-digit character or template after YYYY, - otherwise the year is always interpreted as 4 digits. For example - (with the year 20000): - to_date('200001130', 'YYYYMMDD') will be - interpreted as a 4-digit year; instead use a non-digit - separator after the year, like - to_date('20000-1130', 'YYYY-MMDD') or - to_date('20000Nov30', 'YYYYMonDD'). - - - - - - In to_timestamp and to_date, - the CC (century) field is accepted but ignored - if there is a YYY, YYYY or - Y,YYY field. If CC is used with - YY or Y then the result is - computed as that year in the specified century. If the century is - specified but the year is not, the first year of the century - is assumed. - - - - - - In to_timestamp and to_date, - weekday names or numbers (DAY, D, - and related field types) are accepted but are ignored for purposes of - computing the result. The same is true for quarter - (Q) fields. - - - - - - In to_timestamp and to_date, - an ISO 8601 week-numbering date (as distinct from a Gregorian date) - can be specified in one of two ways: - - - - Year, week number, and weekday: for - example to_date('2006-42-4', 'IYYY-IW-ID') - returns the date 2006-10-19. - If you omit the weekday it is assumed to be 1 (Monday). - - - - - Year and day of year: for example to_date('2006-291', - 'IYYY-IDDD') also returns 2006-10-19. - - - - - - Attempting to enter a date using a mixture of ISO 8601 week-numbering - fields and Gregorian date fields is nonsensical, and will cause an - error. In the context of an ISO 8601 week-numbering year, the - concept of a month or day of month has no - meaning. In the context of a Gregorian year, the ISO week has no - meaning. - - - - While to_date will reject a mixture of - Gregorian and ISO week-numbering date - fields, to_char will not, since output format - specifications like YYYY-MM-DD (IYYY-IDDD) can be - useful. But avoid writing something like IYYY-MM-DD; - that would yield surprising results near the start of the year. - (See for more - information.) - - - - - - - In to_timestamp, millisecond - (MS) or microsecond (US) - fields are used as the - seconds digits after the decimal point. For example - to_timestamp('12.3', 'SS.MS') is not 3 milliseconds, - but 300, because the conversion treats it as 12 + 0.3 seconds. - So, for the format SS.MS, the input values - 12.3, 12.30, - and 12.300 specify the - same number of milliseconds. To get three milliseconds, one must write - 12.003, which the conversion treats as - 12 + 0.003 = 12.003 seconds. - - - - Here is a more - complex example: - to_timestamp('15:12:02.020.001230', 'HH24:MI:SS.MS.US') - is 15 hours, 12 minutes, and 2 seconds + 20 milliseconds + - 1230 microseconds = 2.021230 seconds. - - - - - - to_char(..., 'ID')'s day of the week numbering - matches the extract(isodow from ...) function, but - to_char(..., 'D')'s does not match - extract(dow from ...)'s day numbering. - - - - - - to_char(interval) formats HH and - HH12 as shown on a 12-hour clock, for example zero hours - and 36 hours both output as 12, while HH24 - outputs the full hour value, which can exceed 23 in - an interval value. - - - - - - - - shows the - template patterns available for formatting numeric values. - - - - Template Patterns for Numeric Formatting - - - - Pattern - Description - - - - - 9 - digit position (can be dropped if insignificant) - - - 0 - digit position (will not be dropped, even if insignificant) - - - . (period) - decimal point - - - , (comma) - group (thousands) separator - - - PR - negative value in angle brackets - - - S - sign anchored to number (uses locale) - - - L - currency symbol (uses locale) - - - D - decimal point (uses locale) - - - G - group separator (uses locale) - - - MI - minus sign in specified position (if number < 0) - - - PL - plus sign in specified position (if number > 0) - - - SG - plus/minus sign in specified position - - - RN or rn - Roman numeral (values between 1 and 3999) - - - TH or th - ordinal number suffix - - - V - shift specified number of digits (see notes) - - - EEEE - exponent for scientific notation - - - -

- - - Usage notes for numeric formatting: - - - - - 0 specifies a digit position that will always be printed, - even if it contains a leading/trailing zero. 9 also - specifies a digit position, but if it is a leading zero then it will - be replaced by a space, while if it is a trailing zero and fill mode - is specified then it will be deleted. (For to_number(), - these two pattern characters are equivalent.) - - - - - - If the format provides fewer fractional digits than the number being - formatted, to_char() will round the number to - the specified number of fractional digits. - - - - - - The pattern characters S, L, D, - and G represent the sign, currency symbol, decimal point, - and thousands separator characters defined by the current locale - (see - and ). The pattern characters period - and comma represent those exact characters, with the meanings of - decimal point and thousands separator, regardless of locale. - - - - - - If no explicit provision is made for a sign - in to_char()'s pattern, one column will be reserved for - the sign, and it will be anchored to (appear just left of) the - number. If S appears just left of some 9's, - it will likewise be anchored to the number. - - - - - - A sign formatted using SG, PL, or - MI is not anchored to - the number; for example, - to_char(-12, 'MI9999') produces '- 12' - but to_char(-12, 'S9999') produces ' -12'. - (The Oracle implementation does not allow the use of - MI before 9, but rather - requires that 9 precede - MI.) - - - - - - TH does not convert values less than zero - and does not convert fractional numbers. - - - - - - PL, SG, and - TH are PostgreSQL - extensions. - - - - - - In to_number, if non-data template patterns such - as L or TH are used, the - corresponding number of input characters are skipped, whether or not - they match the template pattern, unless they are data characters - (that is, digits, sign, decimal point, or comma). For - example, TH would skip two non-data characters. - - - - - - V with to_char - multiplies the input values by - 10^n, where - n is the number of digits following - V. V with - to_number divides in a similar manner. - The V can be thought of as marking the position - of an implicit decimal point in the input or output string. - to_char and to_number - do not support the use of - V combined with a decimal point - (e.g., 99.9V99 is not allowed). - - - - - - EEEE (scientific notation) cannot be used in - combination with any of the other formatting patterns or - modifiers other than digit and decimal point patterns, and must be at the end of the format string - (e.g., 9.99EEEE is a valid pattern). - - - - - - In to_number(), the RN - pattern converts Roman numerals (in standard form) to numbers. - Input is case-insensitive, so RN - and rn are equivalent. RN - cannot be used in combination with any other formatting patterns or - modifiers except FM, which is applicable only - in to_char() and is ignored - in to_number(). - - - - - - - Certain modifiers can be applied to any template pattern to alter its - behavior. For example, FM99.99 - is the 99.99 pattern with the - FM modifier. - shows the - modifier patterns for numeric formatting. - - - - Template Pattern Modifiers for Numeric Formatting - - - - Modifier - Description - Example - - - - - FM prefix - fill mode (suppress trailing zeroes and padding blanks) - FM99.99 - - - TH suffix - upper case ordinal number suffix - 999TH - - - th suffix - lower case ordinal number suffix - 999th - - - -

- - - shows some - examples of the use of the to_char function. - - - - <function>to_char</function> Examples - - - - Expression - Result - - - - - to_char(current_timestamp, 'Day, DD HH12:MI:SS') - 'Tuesday , 06 05:39:18' - - - to_char(current_timestamp, 'FMDay, FMDD HH12:MI:SS') - 'Tuesday, 6 05:39:18' - - - to_char(current_timestamp AT TIME ZONE - 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"') - '2022-12-06T05:39:18Z', - ISO 8601 extended format - - - to_char(-0.1, '99.99') - ' -.10' - - - to_char(-0.1, 'FM9.99') - '-.1' - - - to_char(-0.1, 'FM90.99') - '-0.1' - - - to_char(0.1, '0.9') - ' 0.1' - - - to_char(12, '9990999.9') - ' 0012.0' - - - to_char(12, 'FM9990999.9') - '0012.' - - - to_char(485, '999') - ' 485' - - - to_char(-485, '999') - '-485' - - - to_char(485, '9 9 9') - ' 4 8 5' - - - to_char(1485, '9,999') - ' 1,485' - - - to_char(1485, '9G999') - ' 1 485' - - - to_char(148.5, '999.999') - ' 148.500' - - - to_char(148.5, 'FM999.999') - '148.5' - - - to_char(148.5, 'FM999.990') - '148.500' - - - to_char(148.5, '999D999') - ' 148,500' - - - to_char(3148.5, '9G999D999') - ' 3 148,500' - - - to_char(-485, '999S') - '485-' - - - to_char(-485, '999MI') - '485-' - - - to_char(485, '999MI') - '485 ' - - - to_char(485, 'FM999MI') - '485' - - - to_char(485, 'PL999') - '+485' - - - to_char(485, 'SG999') - '+485' - - - to_char(-485, 'SG999') - '-485' - - - to_char(-485, '9SG99') - '4-85' - - - to_char(-485, '999PR') - '<485>' - - - to_char(485, 'L999') - 'DM 485' - - - to_char(485, 'RN') - ' CDLXXXV' - - - to_char(485, 'FMRN') - 'CDLXXXV' - - - to_char(5.2, 'FMRN') - 'V' - - - to_char(482, '999th') - ' 482nd' - - - to_char(485, '"Good number:"999') - 'Good number: 485' - - - to_char(485.8, '"Pre:"999" Post:" .999') - 'Pre: 485 Post: .800' - - - to_char(12, '99V999') - ' 12000' - - - to_char(12.4, '99V999') - ' 12400' - - - to_char(12.45, '99V9') - ' 125' - - - to_char(0.0004859, '9.99EEEE') - ' 4.86e-04' - - - -

- - - - - - Date/Time Functions and Operators - - - shows the available - functions for date/time value processing, with details appearing in - the following subsections. illustrates the behaviors of - the basic arithmetic operators (+, - *, etc.). For formatting functions, refer to - . You should be familiar with - the background information on date/time data types from . - - - - In addition, the usual comparison operators shown in - are available for the - date/time types. Dates and timestamps (with or without time zone) are - all comparable, while times (with or without time zone) and intervals - can only be compared to other values of the same data type. When - comparing a timestamp without time zone to a timestamp with time zone, - the former value is assumed to be given in the time zone specified by - the configuration parameter, and is - rotated to UTC for comparison to the latter value (which is already - in UTC internally). Similarly, a date value is assumed to represent - midnight in the TimeZone zone when comparing it - to a timestamp. - - - - All the functions and operators described below that take time or timestamp - inputs actually come in two variants: one that takes time with time zone or timestamp - with time zone, and one that takes time without time zone or timestamp without time zone. - For brevity, these variants are not shown separately. Also, the - + and * operators come in commutative pairs (for - example both date + integer - and integer + date); we show - only one of each such pair. - - - - Date/Time Operators - - - - - - Operator - - - Description - - - Example(s) - - - - - - - - date + integer - date - - - Add a number of days to a date - - - date '2001-09-28' + 7 - 2001-10-05 - - - - - - date + interval - timestamp - - - Add an interval to a date - - - date '2001-09-28' + interval '1 hour' - 2001-09-28 01:00:00 - - - - - - date + time - timestamp - - - Add a time-of-day to a date - - - date '2001-09-28' + time '03:00' - 2001-09-28 03:00:00 - - - - - - interval + interval - interval - - - Add intervals - - - interval '1 day' + interval '1 hour' - 1 day 01:00:00 - - - - - - timestamp + interval - timestamp - - - Add an interval to a timestamp - - - timestamp '2001-09-28 01:00' + interval '23 hours' - 2001-09-29 00:00:00 - - - - - - time + interval - time - - - Add an interval to a time - - - time '01:00' + interval '3 hours' - 04:00:00 - - - - - - - interval - interval - - - Negate an interval - - - - interval '23 hours' - -23:00:00 - - - - - - date - date - integer - - - Subtract dates, producing the number of days elapsed - - - date '2001-10-01' - date '2001-09-28' - 3 - - - - - - date - integer - date - - - Subtract a number of days from a date - - - date '2001-10-01' - 7 - 2001-09-24 - - - - - - date - interval - timestamp - - - Subtract an interval from a date - - - date '2001-09-28' - interval '1 hour' - 2001-09-27 23:00:00 - - - - - - time - time - interval - - - Subtract times - - - time '05:00' - time '03:00' - 02:00:00 - - - - - - time - interval - time - - - Subtract an interval from a time - - - time '05:00' - interval '2 hours' - 03:00:00 - - - - - - timestamp - interval - timestamp - - - Subtract an interval from a timestamp - - - timestamp '2001-09-28 23:00' - interval '23 hours' - 2001-09-28 00:00:00 - - - - - - interval - interval - interval - - - Subtract intervals - - - interval '1 day' - interval '1 hour' - 1 day -01:00:00 - - - - - - timestamp - timestamp - interval - - - Subtract timestamps (converting 24-hour intervals into days, - similarly to justify_hours()) - - - timestamp '2001-09-29 03:00' - timestamp '2001-07-27 12:00' - 63 days 15:00:00 - - - - - - interval * double precision - interval - - - Multiply an interval by a scalar - - - interval '1 second' * 900 - 00:15:00 - - - interval '1 day' * 21 - 21 days - - - interval '1 hour' * 3.5 - 03:30:00 - - - - - - interval / double precision - interval - - - Divide an interval by a scalar - - - interval '1 hour' / 1.5 - 00:40:00 - - - - -

- - - Date/Time Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - age - - age ( timestamp, timestamp ) - interval - - - Subtract arguments, producing a symbolic result that - uses years and months, rather than just days - - - age(timestamp '2001-04-10', timestamp '1957-06-13') - 43 years 9 mons 27 days - - - - - - age ( timestamp ) - interval - - - Subtract argument from current_date (at midnight) - - - age(timestamp '1957-06-13') - 62 years 6 mons 10 days - - - - - - - clock_timestamp - - clock_timestamp ( ) - timestamp with time zone - - - Current date and time (changes during statement execution); - see - - - clock_timestamp() - 2019-12-23 14:39:53.662522-05 - - - - - - - current_date - - current_date - date - - - Current date; see - - - current_date - 2019-12-23 - - - - - - - current_time - - current_time - time with time zone - - - Current time of day; see - - - current_time - 14:39:53.662522-05 - - - - - - current_time ( integer ) - time with time zone - - - Current time of day, with limited precision; - see - - - current_time(2) - 14:39:53.66-05 - - - - - - - current_timestamp - - current_timestamp - timestamp with time zone - - - Current date and time (start of current transaction); - see - - - current_timestamp - 2019-12-23 14:39:53.662522-05 - - - - - - current_timestamp ( integer ) - timestamp with time zone - - - Current date and time (start of current transaction), with limited precision; - see - - - current_timestamp(0) - 2019-12-23 14:39:53-05 - - - - - - - date_add - - date_add ( timestamp with time zone, interval , text ) - timestamp with time zone - - - Add an interval to a timestamp with time - zone, computing times of day and daylight-savings adjustments - according to the time zone named by the third argument, or the - current setting if that is omitted. - The form with two arguments is equivalent to the timestamp with - time zone + interval operator. - - - date_add('2021-10-31 00:00:00+02'::timestamptz, '1 day'::interval, 'Europe/Warsaw') - 2021-10-31 23:00:00+00 - - - - - - date_bin ( interval, timestamp, timestamp ) - timestamp - - - Bin input into specified interval aligned with specified origin; see - - - date_bin('15 minutes', timestamp '2001-02-16 20:38:40', timestamp '2001-02-16 20:05:00') - 2001-02-16 20:35:00 - - - - - - - date_part - - date_part ( text, timestamp ) - double precision - - - Get timestamp subfield (equivalent to extract); - see - - - date_part('hour', timestamp '2001-02-16 20:38:40') - 20 - - - - - - date_part ( text, interval ) - double precision - - - Get interval subfield (equivalent to extract); - see - - - date_part('month', interval '2 years 3 months') - 3 - - - - - - - date_subtract - - date_subtract ( timestamp with time zone, interval , text ) - timestamp with time zone - - - Subtract an interval from a timestamp with time - zone, computing times of day and daylight-savings adjustments - according to the time zone named by the third argument, or the - current setting if that is omitted. - The form with two arguments is equivalent to the timestamp with - time zone - interval operator. - - - date_subtract('2021-11-01 00:00:00+01'::timestamptz, '1 day'::interval, 'Europe/Warsaw') - 2021-10-30 22:00:00+00 - - - - - - - date_trunc - - date_trunc ( text, timestamp ) - timestamp - - - Truncate to specified precision; see - - - date_trunc('hour', timestamp '2001-02-16 20:38:40') - 2001-02-16 20:00:00 - - - - - - date_trunc ( text, timestamp with time zone, text ) - timestamp with time zone - - - Truncate to specified precision in the specified time zone; see - - - - date_trunc('day', timestamptz '2001-02-16 20:38:40+00', 'Australia/Sydney') - 2001-02-16 13:00:00+00 - - - - - - date_trunc ( text, interval ) - interval - - - Truncate to specified precision; see - - - - date_trunc('hour', interval '2 days 3 hours 40 minutes') - 2 days 03:00:00 - - - - - - - extract - - extract ( field from timestamp ) - numeric - - - Get timestamp subfield; see - - - extract(hour from timestamp '2001-02-16 20:38:40') - 20 - - - - - - extract ( field from interval ) - numeric - - - Get interval subfield; see - - - extract(month from interval '2 years 3 months') - 3 - - - - - - - isfinite - - isfinite ( date ) - boolean - - - Test for finite date (not +/-infinity) - - - isfinite(date '2001-02-16') - true - - - - - - isfinite ( timestamp ) - boolean - - - Test for finite timestamp (not +/-infinity) - - - isfinite(timestamp 'infinity') - false - - - - - - isfinite ( interval ) - boolean - - - Test for finite interval (not +/-infinity) - - - isfinite(interval '4 hours') - true - - - - - - - justify_days - - justify_days ( interval ) - interval - - - Adjust interval, converting 30-day time periods to months - - - justify_days(interval '1 year 65 days') - 1 year 2 mons 5 days - - - - - - - justify_hours - - justify_hours ( interval ) - interval - - - Adjust interval, converting 24-hour time periods to days - - - justify_hours(interval '50 hours 10 minutes') - 2 days 02:10:00 - - - - - - - justify_interval - - justify_interval ( interval ) - interval - - - Adjust interval using justify_days - and justify_hours, with additional sign - adjustments - - - justify_interval(interval '1 mon -1 hour') - 29 days 23:00:00 - - - - - - - localtime - - localtime - time - - - Current time of day; - see - - - localtime - 14:39:53.662522 - - - - - - localtime ( integer ) - time - - - Current time of day, with limited precision; - see - - - localtime(0) - 14:39:53 - - - - - - - localtimestamp - - localtimestamp - timestamp - - - Current date and time (start of current transaction); - see - - - localtimestamp - 2019-12-23 14:39:53.662522 - - - - - - localtimestamp ( integer ) - timestamp - - - Current date and time (start of current - transaction), with limited precision; - see - - - localtimestamp(2) - 2019-12-23 14:39:53.66 - - - - - - - make_date - - make_date ( year int, - month int, - day int ) - date - - - Create date from year, month and day fields - (negative years signify BC) - - - make_date(2013, 7, 15) - 2013-07-15 - - - - - - make_interval - - make_interval ( years int - , months int - , weeks int - , days int - , hours int - , mins int - , secs double precision - ) - interval - - - Create interval from years, months, weeks, days, hours, minutes and - seconds fields, each of which can default to zero - - - make_interval(days => 10) - 10 days - - - - - - - make_time - - make_time ( hour int, - min int, - sec double precision ) - time - - - Create time from hour, minute and seconds fields - - - make_time(8, 15, 23.5) - 08:15:23.5 - - - - - - - make_timestamp - - make_timestamp ( year int, - month int, - day int, - hour int, - min int, - sec double precision ) - timestamp - - - Create timestamp from year, month, day, hour, minute and seconds fields - (negative years signify BC) - - - make_timestamp(2013, 7, 15, 8, 15, 23.5) - 2013-07-15 08:15:23.5 - - - - - - - make_timestamptz - - make_timestamptz ( year int, - month int, - day int, - hour int, - min int, - sec double precision - , timezone text ) - timestamp with time zone - - - Create timestamp with time zone from year, month, day, hour, minute - and seconds fields (negative years signify BC). - If timezone is not - specified, the current time zone is used; the examples assume the - session time zone is Europe/London - - - make_timestamptz(2013, 7, 15, 8, 15, 23.5) - 2013-07-15 08:15:23.5+01 - - - make_timestamptz(2013, 7, 15, 8, 15, 23.5, 'America/New_York') - 2013-07-15 13:15:23.5+01 - - - - - - - now - - now ( ) - timestamp with time zone - - - Current date and time (start of current transaction); - see - - - now() - 2019-12-23 14:39:53.662522-05 - - - - - - - statement_timestamp - - statement_timestamp ( ) - timestamp with time zone - - - Current date and time (start of current statement); - see - - - statement_timestamp() - 2019-12-23 14:39:53.662522-05 - - - - - - - timeofday - - timeofday ( ) - text - - - Current date and time - (like clock_timestamp, but as a text string); - see - - - timeofday() - Mon Dec 23 14:39:53.662522 2019 EST - - - - - - - transaction_timestamp - - transaction_timestamp ( ) - timestamp with time zone - - - Current date and time (start of current transaction); - see - - - transaction_timestamp() - 2019-12-23 14:39:53.662522-05 - - - - - - - to_timestamp - - to_timestamp ( double precision ) - timestamp with time zone - - - Convert Unix epoch (seconds since 1970-01-01 00:00:00+00) to - timestamp with time zone - - - to_timestamp(1284352323) - 2010-09-13 04:32:03+00 - - - - -

- - - - OVERLAPS - - In addition to these functions, the SQL OVERLAPS operator is - supported: - -(start1, end1) OVERLAPS (start2, end2) -(start1, length1) OVERLAPS (start2, length2) - - This expression yields true when two time periods (defined by their - endpoints) overlap, false when they do not overlap. The endpoints - can be specified as pairs of dates, times, or time stamps; or as - a date, time, or time stamp followed by an interval. When a pair - of values is provided, either the start or the end can be written - first; OVERLAPS automatically takes the earlier value - of the pair as the start. Each time period is considered to - represent the half-open interval start <= - time < end, unless - start and end are equal in which case it - represents that single time instant. This means for instance that two - time periods with only an endpoint in common do not overlap. - - - -SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS - (DATE '2001-10-30', DATE '2002-10-30'); -Result: true -SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS - (DATE '2001-10-30', DATE '2002-10-30'); -Result: false -SELECT (DATE '2001-10-29', DATE '2001-10-30') OVERLAPS - (DATE '2001-10-30', DATE '2001-10-31'); -Result: false -SELECT (DATE '2001-10-30', DATE '2001-10-30') OVERLAPS - (DATE '2001-10-30', DATE '2001-10-31'); -Result: true - - - - When adding an interval value to (or subtracting an - interval value from) a timestamp - or timestamp with time zone value, the months, days, and - microseconds fields of the interval value are handled in turn. - First, a nonzero months field advances or decrements the date of the - timestamp by the indicated number of months, keeping the day of month the - same unless it would be past the end of the new month, in which case the - last day of that month is used. (For example, March 31 plus 1 month - becomes April 30, but March 31 plus 2 months becomes May 31.) - Then the days field advances or decrements the date of the timestamp by - the indicated number of days. In both these steps the local time of day - is kept the same. Finally, if there is a nonzero microseconds field, it - is added or subtracted literally. - When doing arithmetic on a timestamp with time zone value in - a time zone that recognizes DST, this means that adding or subtracting - (say) interval '1 day' does not necessarily have the - same result as adding or subtracting interval '24 - hours'. - For example, with the session time zone set - to America/Denver: - -SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '1 day'; -Result: 2005-04-03 12:00:00-06 -SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '24 hours'; -Result: 2005-04-03 13:00:00-06 - - This happens because an hour was skipped due to a change in daylight saving - time at 2005-04-03 02:00:00 in time zone - America/Denver. - - - - Note there can be ambiguity in the months field returned by - age because different months have different numbers of - days. PostgreSQL's approach uses the month from the - earlier of the two dates when calculating partial months. For example, - age('2004-06-01', '2004-04-30') uses April to yield - 1 mon 1 day, while using May would yield 1 mon 2 - days because May has 31 days, while April has only 30. - - - - Subtraction of dates and timestamps can also be complex. One conceptually - simple way to perform subtraction is to convert each value to a number - of seconds using EXTRACT(EPOCH FROM ...), then subtract the - results; this produces the - number of seconds between the two values. This will adjust - for the number of days in each month, timezone changes, and daylight - saving time adjustments. Subtraction of date or timestamp - values with the - operator - returns the number of days (24-hours) and hours/minutes/seconds - between the values, making the same adjustments. The age - function returns years, months, days, and hours/minutes/seconds, - performing field-by-field subtraction and then adjusting for negative - field values. The following queries illustrate the differences in these - approaches. The sample results were produced with timezone - = 'US/Eastern'; there is a daylight saving time change between the - two dates used: - - - -SELECT EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') - - EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00'); -Result: 10537200.000000 -SELECT (EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') - - EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00')) - / 60 / 60 / 24; -Result: 121.9583333333333333 -SELECT timestamptz '2013-07-01 12:00:00' - timestamptz '2013-03-01 12:00:00'; -Result: 121 days 23:00:00 -SELECT age(timestamptz '2013-07-01 12:00:00', timestamptz '2013-03-01 12:00:00'); -Result: 4 mons - - - - <function>EXTRACT</function>, <function>date_part</function> - - - date_part - - - extract - - - -EXTRACT(field FROM source) - - - - The extract function retrieves subfields - such as year or hour from date/time values. - source must be a value expression of - type timestamp, date, time, - or interval. (Timestamps and times can be with or - without time zone.) - field is an identifier or - string that selects what field to extract from the source value. - Not all fields are valid for every input data type; for example, fields - smaller than a day cannot be extracted from a date, while - fields of a day or more cannot be extracted from a time. - The extract function returns values of type - numeric. - - - - The following are valid field names: - - - - - century - - - The century; for interval values, the year field - divided by 100 - - - -SELECT EXTRACT(CENTURY FROM TIMESTAMP '2000-12-16 12:21:13'); -Result: 20 -SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 21 -SELECT EXTRACT(CENTURY FROM DATE '0001-01-01 AD'); -Result: 1 -SELECT EXTRACT(CENTURY FROM DATE '0001-12-31 BC'); -Result: -1 -SELECT EXTRACT(CENTURY FROM INTERVAL '2001 years'); -Result: 20 - - - - - - day - - - The day of the month (1–31); for interval - values, the number of days - - - -SELECT EXTRACT(DAY FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 16 -SELECT EXTRACT(DAY FROM INTERVAL '40 days 1 minute'); -Result: 40 - - - - - - - decade - - - The year field divided by 10 - - - -SELECT EXTRACT(DECADE FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 200 - - - - - - dow - - - The day of the week as Sunday (0) to - Saturday (6) - - - -SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 5 - - - Note that extract's day of the week numbering - differs from that of the to_char(..., - 'D') function. - - - - - - - doy - - - The day of the year (1–365/366) - - - -SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 47 - - - - - - epoch - - - For timestamp with time zone values, the - number of seconds since 1970-01-01 00:00:00 UTC (negative for - timestamps before that); - for date and timestamp values, the - nominal number of seconds since 1970-01-01 00:00:00, - without regard to timezone or daylight-savings rules; - for interval values, the total number - of seconds in the interval - - - -SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40.12-08'); -Result: 982384720.120000 -SELECT EXTRACT(EPOCH FROM TIMESTAMP '2001-02-16 20:38:40.12'); -Result: 982355920.120000 -SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours'); -Result: 442800.000000 - - - - You can convert an epoch value back to a timestamp with time zone - with to_timestamp: - - -SELECT to_timestamp(982384720.12); -Result: 2001-02-17 04:38:40.12+00 - - - - Beware that applying to_timestamp to an epoch - extracted from a date or timestamp value - could produce a misleading result: the result will effectively - assume that the original value had been given in UTC, which might - not be the case. - - - - - - hour - - - The hour field (0–23 in timestamps, unrestricted in - intervals) - - - -SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 20 - - - - - - isodow - - - The day of the week as Monday (1) to - Sunday (7) - - - -SELECT EXTRACT(ISODOW FROM TIMESTAMP '2001-02-18 20:38:40'); -Result: 7 - - - This is identical to dow except for Sunday. This - matches the ISO 8601 day of the week numbering. - - - - - - - isoyear - - - The ISO 8601 week-numbering year that the date - falls in - - - -SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-01'); -Result: 2005 -SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-02'); -Result: 2006 - - - - Each ISO 8601 week-numbering year begins with the - Monday of the week containing the 4th of January, so in early - January or late December the ISO year may be - different from the Gregorian year. See the week - field for more information. - - - - - - julian - - - The Julian Date corresponding to the - date or timestamp. Timestamps - that are not local midnight result in a fractional value. See - for more information. - - - -SELECT EXTRACT(JULIAN FROM DATE '2006-01-01'); -Result: 2453737 -SELECT EXTRACT(JULIAN FROM TIMESTAMP '2006-01-01 12:00'); -Result: 2453737.50000000000000000000 - - - - - - microseconds - - - The seconds field, including fractional parts, multiplied by 1 - 000 000; note that this includes full seconds - - - -SELECT EXTRACT(MICROSECONDS FROM TIME '17:12:28.5'); -Result: 28500000 - - - - - - millennium - - - The millennium; for interval values, the year field - divided by 1000 - - - -SELECT EXTRACT(MILLENNIUM FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 3 -SELECT EXTRACT(MILLENNIUM FROM INTERVAL '2001 years'); -Result: 2 - - - - Years in the 1900s are in the second millennium. - The third millennium started January 1, 2001. - - - - - - milliseconds - - - The seconds field, including fractional parts, multiplied by - 1000. Note that this includes full seconds. - - - -SELECT EXTRACT(MILLISECONDS FROM TIME '17:12:28.5'); -Result: 28500.000 - - - - - - minute - - - The minutes field (0–59) - - - -SELECT EXTRACT(MINUTE FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 38 - - - - - - month - - - The number of the month within the year (1–12); - for interval values, the number of months modulo 12 - (0–11) - - - -SELECT EXTRACT(MONTH FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 2 -SELECT EXTRACT(MONTH FROM INTERVAL '2 years 3 months'); -Result: 3 -SELECT EXTRACT(MONTH FROM INTERVAL '2 years 13 months'); -Result: 1 - - - - - - quarter - - - The quarter of the year (1–4) that the date is in; - for interval values, the month field divided by 3 - plus 1 - - - -SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 1 -SELECT EXTRACT(QUARTER FROM INTERVAL '1 year 6 months'); -Result: 3 - - - - - - second - - - The seconds field, including any fractional seconds - - - -SELECT EXTRACT(SECOND FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 40.000000 -SELECT EXTRACT(SECOND FROM TIME '17:12:28.5'); -Result: 28.500000 - - - - - timezone - - - The time zone offset from UTC, measured in seconds. Positive values - correspond to time zones east of UTC, negative values to - zones west of UTC. (Technically, - PostgreSQL does not use UTC because - leap seconds are not handled.) - - - - - - timezone_hour - - - The hour component of the time zone offset - - - - - - timezone_minute - - - The minute component of the time zone offset - - - - - - week - - - The number of the ISO 8601 week-numbering week of - the year. By definition, ISO weeks start on Mondays and the first - week of a year contains January 4 of that year. In other words, the - first Thursday of a year is in week 1 of that year. - - - In the ISO week-numbering system, it is possible for early-January - dates to be part of the 52nd or 53rd week of the previous year, and for - late-December dates to be part of the first week of the next year. - For example, 2005-01-01 is part of the 53rd week of year - 2004, and 2006-01-01 is part of the 52nd week of year - 2005, while 2012-12-31 is part of the first week of 2013. - It's recommended to use the isoyear field together with - week to get consistent results. - - - - For interval values, the week field is simply the number - of integral days divided by 7. - - - -SELECT EXTRACT(WEEK FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 7 -SELECT EXTRACT(WEEK FROM INTERVAL '13 days 24 hours'); -Result: 1 - - - - - - year - - - The year field. Keep in mind there is no 0 AD, so subtracting - BC years from AD years should be done with care. - - - -SELECT EXTRACT(YEAR FROM TIMESTAMP '2001-02-16 20:38:40'); -Result: 2001 - - - - - - - - - When processing an interval value, - the extract function produces field values that - match the interpretation used by the interval output function. This - can produce surprising results if one starts with a non-normalized - interval representation, for example: - -SELECT INTERVAL '80 minutes'; -Result: 01:20:00 -SELECT EXTRACT(MINUTES FROM INTERVAL '80 minutes'); -Result: 20 - - - - - - When the input value is +/-Infinity, extract returns - +/-Infinity for monotonically-increasing fields (epoch, - julian, year, isoyear, - decade, century, and millennium - for timestamp inputs; epoch, hour, - day, year, decade, - century, and millennium for - interval inputs). - For other fields, NULL is returned. PostgreSQL - versions before 9.6 returned zero for all cases of infinite input. - - - - - The extract function is primarily intended - for computational processing. For formatting date/time values for - display, see . - - - - The date_part function is modeled on the traditional - Ingres equivalent to the - SQL-standard function extract: - -date_part('field', source) - - Note that here the field parameter needs to - be a string value, not a name. The valid field names for - date_part are the same as for - extract. - For historical reasons, the date_part function - returns values of type double precision. This can result in - a loss of precision in certain uses. Using extract - is recommended instead. - - - -SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40'); -Result: 16 -SELECT date_part('hour', INTERVAL '4 hours 3 minutes'); -Result: 4 - - - - - - <function>date_trunc</function> - - - date_trunc - - - - The function date_trunc is conceptually - similar to the trunc function for numbers. - - - - -date_trunc(field, source , time_zone ) - - source is a value expression of type - timestamp, timestamp with time zone, - or interval. - (Values of type date and - time are cast automatically to timestamp or - interval, respectively.) - field selects to which precision to - truncate the input value. The return value is likewise of type - timestamp, timestamp with time zone, - or interval, - and it has all fields that are less significant than the - selected one set to zero (or one, for day and month). - - - - Valid values for field are: - - microseconds - milliseconds - second - minute - hour - day - week - month - quarter - year - decade - century - millennium - - - - - When the input value is of type timestamp with time zone, - the truncation is performed with respect to a particular time zone; - for example, truncation to day produces a value that - is midnight in that zone. By default, truncation is done with respect - to the current setting, but the - optional time_zone argument can be provided - to specify a different time zone. The time zone name can be specified - in any of the ways described in . - - - - A time zone cannot be specified when processing timestamp without - time zone or interval inputs. These are always - taken at face value. - - - - Examples (assuming the local time zone is America/New_York): - -SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40'); -Result: 2001-02-16 20:00:00 -SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40'); -Result: 2001-01-01 00:00:00 -SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00'); -Result: 2001-02-16 00:00:00-05 -SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00', 'Australia/Sydney'); -Result: 2001-02-16 08:00:00-05 -SELECT date_trunc('hour', INTERVAL '3 days 02:47:33'); -Result: 3 days 02:00:00 - - - - - - <function>date_bin</function> - - - date_bin - - - - The function date_bin bins the input - timestamp into the specified interval (the stride) - aligned with a specified origin. - - - - -date_bin(stride, source, origin) - - source is a value expression of type - timestamp or timestamp with time zone. (Values - of type date are cast automatically to - timestamp.) stride is a value - expression of type interval. The return value is likewise - of type timestamp or timestamp with time zone, - and it marks the beginning of the bin into which the - source is placed. - - - - Examples: - -SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01'); -Result: 2020-02-11 15:30:00 -SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01 00:02:30'); -Result: 2020-02-11 15:32:30 - - - - - In the case of full units (1 minute, 1 hour, etc.), it gives the same result as - the analogous date_trunc call, but the difference is - that date_bin can truncate to an arbitrary interval. - - - - The stride interval must be greater than zero and - cannot contain units of month or larger. - - - - - <literal>AT TIME ZONE</literal> and <literal>AT LOCAL</literal> - - - time zone - conversion - - - - AT TIME ZONE - - - - AT LOCAL - - - - The AT TIME ZONE operator converts time - stamp without time zone to/from - time stamp with time zone, and - time with time zone values to different time - zones. shows its - variants. - - - - <literal>AT TIME ZONE</literal> and <literal>AT LOCAL</literal> Variants - - - - - Operator - - - Description - - - Example(s) - - - - - - - - timestamp without time zone AT TIME ZONE zone - timestamp with time zone - - - Converts given time stamp without time zone to - time stamp with time zone, assuming the given - value is in the named time zone. - - - timestamp '2001-02-16 20:38:40' at time zone 'America/Denver' - 2001-02-17 03:38:40+00 - - - - - - timestamp without time zone AT LOCAL - timestamp with time zone - - - Converts given time stamp without time zone to - time stamp with the session's - TimeZone value as time zone. - - - timestamp '2001-02-16 20:38:40' at local - 2001-02-17 03:38:40+00 - - - - - - timestamp with time zone AT TIME ZONE zone - timestamp without time zone - - - Converts given time stamp with time zone to - time stamp without time zone, as the time would - appear in that zone. - - - timestamp with time zone '2001-02-16 20:38:40-05' at time zone 'America/Denver' - 2001-02-16 18:38:40 - - - - - - timestamp with time zone AT LOCAL - timestamp without time zone - - - Converts given time stamp with time zone to - time stamp without time zone, as the time would - appear with the session's TimeZone value as time zone. - - - timestamp with time zone '2001-02-16 20:38:40-05' at local - 2001-02-16 18:38:40 - - - - - - time with time zone AT TIME ZONE zone - time with time zone - - - Converts given time with time zone to a new time - zone. Since no date is supplied, this uses the currently active UTC - offset for the named destination zone. - - - time with time zone '05:34:17-05' at time zone 'UTC' - 10:34:17+00 - - - - - - time with time zone AT LOCAL - time with time zone - - - Converts given time with time zone to a new time - zone. Since no date is supplied, this uses the currently active UTC - offset for the session's TimeZone value. - - - Assuming the session's TimeZone is set to UTC: - - - time with time zone '05:34:17-05' at local - 10:34:17+00 - - - - -

- - - In these expressions, the desired time zone zone can be - specified either as a text value (e.g., 'America/Los_Angeles') - or as an interval (e.g., INTERVAL '-08:00'). - In the text case, a time zone name can be specified in any of the ways - described in . - The interval case is only useful for zones that have fixed offsets from - UTC, so it is not very common in practice. - - - - The syntax AT LOCAL may be used as shorthand for - AT TIME ZONE local, where - local is the session's - TimeZone value. - - - - Examples (assuming the current setting - is America/Los_Angeles): - -SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'America/Denver'; -Result: 2001-02-16 19:38:40-08 -SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'America/Denver'; -Result: 2001-02-16 18:38:40 -SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'Asia/Tokyo' AT TIME ZONE 'America/Chicago'; -Result: 2001-02-16 05:38:40 -SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT LOCAL; -Result: 2001-02-16 17:38:40 -SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE '+05'; -Result: 2001-02-16 20:38:40 -SELECT TIME WITH TIME ZONE '20:38:40-05' AT LOCAL; -Result: 17:38:40 - - The first example adds a time zone to a value that lacks it, and - displays the value using the current TimeZone - setting. The second example shifts the time stamp with time zone value - to the specified time zone, and returns the value without a time zone. - This allows storage and display of values different from the current - TimeZone setting. The third example converts - Tokyo time to Chicago time. The fourth example shifts the time stamp - with time zone value to the time zone currently specified by the - TimeZone setting and returns the value without a - time zone. The fifth example demonstrates that the sign in a POSIX-style - time zone specification has the opposite meaning of the sign in an - ISO-8601 datetime literal, as described in - and . - - - - The sixth example is a cautionary tale. Due to the fact that there is no - date associated with the input value, the conversion is made using the - current date of the session. Therefore, this static example may show a wrong - result depending on the time of the year it is viewed because - 'America/Los_Angeles' observes Daylight Savings Time. - - - - The function timezone(zone, - timestamp) is equivalent to the SQL-conforming construct - timestamp AT TIME ZONE - zone. - - - - The function timezone(zone, - time) is equivalent to the SQL-conforming construct - time AT TIME ZONE - zone. - - - - The function timezone(timestamp) - is equivalent to the SQL-conforming construct timestamp - AT LOCAL. - - - - The function timezone(time) - is equivalent to the SQL-conforming construct time - AT LOCAL. - - - - - Current Date/Time - - - date - current - - - - time - current - - - - PostgreSQL provides a number of functions - that return values related to the current date and time. These - SQL-standard functions all return values based on the start time of - the current transaction: - -CURRENT_DATE -CURRENT_TIME -CURRENT_TIMESTAMP -CURRENT_TIME(precision) -CURRENT_TIMESTAMP(precision) -LOCALTIME -LOCALTIMESTAMP -LOCALTIME(precision) -LOCALTIMESTAMP(precision) - - - - - CURRENT_TIME and - CURRENT_TIMESTAMP deliver values with time zone; - LOCALTIME and - LOCALTIMESTAMP deliver values without time zone. - - - - CURRENT_TIME, - CURRENT_TIMESTAMP, - LOCALTIME, and - LOCALTIMESTAMP - can optionally take - a precision parameter, which causes the result to be rounded - to that many fractional digits in the seconds field. Without a precision parameter, - the result is given to the full available precision. - - - - Some examples: - -SELECT CURRENT_TIME; -Result: 14:39:53.662522-05 -SELECT CURRENT_DATE; -Result: 2019-12-23 -SELECT CURRENT_TIMESTAMP; -Result: 2019-12-23 14:39:53.662522-05 -SELECT CURRENT_TIMESTAMP(2); -Result: 2019-12-23 14:39:53.66-05 -SELECT LOCALTIMESTAMP; -Result: 2019-12-23 14:39:53.662522 - - - - - Since these functions return - the start time of the current transaction, their values do not - change during the transaction. This is considered a feature: - the intent is to allow a single transaction to have a consistent - notion of the current time, so that multiple - modifications within the same transaction bear the same - time stamp. - - - - - Other database systems might advance these values more - frequently. - - - - - PostgreSQL also provides functions that - return the start time of the current statement, as well as the actual - current time at the instant the function is called. The complete list - of non-SQL-standard time functions is: - -transaction_timestamp() -statement_timestamp() -clock_timestamp() -timeofday() -now() - - - - - transaction_timestamp() is equivalent to - CURRENT_TIMESTAMP, but is named to clearly reflect - what it returns. - statement_timestamp() returns the start time of the current - statement (more specifically, the time of receipt of the latest command - message from the client). - statement_timestamp() and transaction_timestamp() - return the same value during the first statement of a transaction, but might - differ during subsequent statements. - clock_timestamp() returns the actual current time, and - therefore its value changes even within a single SQL statement. - timeofday() is a historical - PostgreSQL function. Like - clock_timestamp(), it returns the actual current time, - but as a formatted text string rather than a timestamp - with time zone value. - now() is a traditional PostgreSQL - equivalent to transaction_timestamp(). - - - - All the date/time data types also accept the special literal value - now to specify the current date and time (again, - interpreted as the transaction start time). Thus, - the following three all return the same result: - -SELECT CURRENT_TIMESTAMP; -SELECT now(); -SELECT TIMESTAMP 'now'; -- but see tip below - - - - - - Do not use the third form when specifying a value to be evaluated later, - for example in a DEFAULT clause for a table column. - The system will convert now - to a timestamp as soon as the constant is parsed, so that when - the default value is needed, - the time of the table creation would be used! The first two - forms will not be evaluated until the default value is used, - because they are function calls. Thus they will give the desired - behavior of defaulting to the time of row insertion. - (See also .) - - - - - - Delaying Execution - - - pg_sleep - - - pg_sleep_for - - - pg_sleep_until - - - sleep - - - delay - - - - The following functions are available to delay execution of the server - process: - -pg_sleep ( double precision ) -pg_sleep_for ( interval ) -pg_sleep_until ( timestamp with time zone ) - - - pg_sleep makes the current session's process - sleep until the given number of seconds have - elapsed. Fractional-second delays can be specified. - pg_sleep_for is a convenience function to - allow the sleep time to be specified as an interval. - pg_sleep_until is a convenience function for when - a specific wake-up time is desired. - For example: - - -SELECT pg_sleep(1.5); -SELECT pg_sleep_for('5 minutes'); -SELECT pg_sleep_until('tomorrow 03:00'); - - - - - - The effective resolution of the sleep interval is platform-specific; - 0.01 seconds is a common value. The sleep delay will be at least as long - as specified. It might be longer depending on factors such as server load. - In particular, pg_sleep_until is not guaranteed to - wake up exactly at the specified time, but it will not wake up any earlier. - - - - - - Make sure that your session does not hold more locks than necessary - when calling pg_sleep or its variants. Otherwise - other sessions might have to wait for your sleeping process, slowing down - the entire system. - - - - - - - - - Enum Support Functions - - - For enum types (described in ), - there are several functions that allow cleaner programming without - hard-coding particular values of an enum type. - These are listed in . The examples - assume an enum type created as: - - -CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple'); - - - - - - Enum Support Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - enum_first - - enum_first ( anyenum ) - anyenum - - - Returns the first value of the input enum type. - - - enum_first(null::rainbow) - red - - - - - - enum_last - - enum_last ( anyenum ) - anyenum - - - Returns the last value of the input enum type. - - - enum_last(null::rainbow) - purple - - - - - - enum_range - - enum_range ( anyenum ) - anyarray - - - Returns all values of the input enum type in an ordered array. - - - enum_range(null::rainbow) - {red,orange,yellow,&zwsp;green,blue,purple} - - - - - enum_range ( anyenum, anyenum ) - anyarray - - - Returns the range between the two given enum values, as an ordered - array. The values must be from the same enum type. If the first - parameter is null, the result will start with the first value of - the enum type. - If the second parameter is null, the result will end with the last - value of the enum type. - - - enum_range('orange'::rainbow, 'green'::rainbow) - {orange,yellow,green} - - - enum_range(NULL, 'green'::rainbow) - {red,orange,&zwsp;yellow,green} - - - enum_range('orange'::rainbow, NULL) - {orange,yellow,green,&zwsp;blue,purple} - - - - -

- - - Notice that except for the two-argument form of enum_range, - these functions disregard the specific value passed to them; they care - only about its declared data type. Either null or a specific value of - the type can be passed, with the same result. It is more common to - apply these functions to a table column or function argument than to - a hardwired type name as used in the examples. - - - - - Geometric Functions and Operators - - - The geometric types point, box, - lseg, line, path, - polygon, and circle have a large set of - native support functions and operators, shown in , , and . - - - - Geometric Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - geometric_type + point - geometric_type - - - Adds the coordinates of the second point to those of each - point of the first argument, thus performing translation. - Available for point, box, path, - circle. - - - box '(1,1),(0,0)' + point '(2,0)' - (3,1),(2,0) - - - - - - path + path - path - - - Concatenates two open paths (returns NULL if either path is closed). - - - path '[(0,0),(1,1)]' + path '[(2,2),(3,3),(4,4)]' - [(0,0),(1,1),(2,2),(3,3),(4,4)] - - - - - - geometric_type - point - geometric_type - - - Subtracts the coordinates of the second point from those - of each point of the first argument, thus performing translation. - Available for point, box, path, - circle. - - - box '(1,1),(0,0)' - point '(2,0)' - (-1,1),(-2,0) - - - - - - geometric_type * point - geometric_type - - - Multiplies each point of the first argument by the second - point (treating a point as being a complex number - represented by real and imaginary parts, and performing standard - complex multiplication). If one interprets - the second point as a vector, this is equivalent to - scaling the object's size and distance from the origin by the length - of the vector, and rotating it counterclockwise around the origin by - the vector's angle from the x axis. - Available for point, box,Rotating a - box with these operators only moves its corner points: the box is - still considered to have sides parallel to the axes. Hence the box's - size is not preserved, as a true rotation would do. - path, circle. - - - path '((0,0),(1,0),(1,1))' * point '(3.0,0)' - ((0,0),(3,0),(3,3)) - - - path '((0,0),(1,0),(1,1))' * point(cosd(45), sind(45)) - ((0,0),&zwsp;(0.7071067811865475,0.7071067811865475),&zwsp;(0,1.414213562373095)) - - - - - - geometric_type / point - geometric_type - - - Divides each point of the first argument by the second - point (treating a point as being a complex number - represented by real and imaginary parts, and performing standard - complex division). If one interprets - the second point as a vector, this is equivalent to - scaling the object's size and distance from the origin down by the - length of the vector, and rotating it clockwise around the origin by - the vector's angle from the x axis. - Available for point, box, path, - circle. - - - path '((0,0),(1,0),(1,1))' / point '(2.0,0)' - ((0,0),(0.5,0),(0.5,0.5)) - - - path '((0,0),(1,0),(1,1))' / point(cosd(45), sind(45)) - ((0,0),&zwsp;(0.7071067811865476,-0.7071067811865476),&zwsp;(1.4142135623730951,0)) - - - - - - @-@ geometric_type - double precision - - - Computes the total length. - Available for lseg, path. - - - @-@ path '[(0,0),(1,0),(1,1)]' - 2 - - - - - - @@ geometric_type - point - - - Computes the center point. - Available for box, lseg, - polygon, circle. - - - @@ box '(2,2),(0,0)' - (1,1) - - - - - - # geometric_type - integer - - - Returns the number of points. - Available for path, polygon. - - - # path '((1,0),(0,1),(-1,0))' - 3 - - - - - - geometric_type # geometric_type - point - - - Computes the point of intersection, or NULL if there is none. - Available for lseg, line. - - - lseg '[(0,0),(1,1)]' # lseg '[(1,0),(0,1)]' - (0.5,0.5) - - - - - - box # box - box - - - Computes the intersection of two boxes, or NULL if there is none. - - - box '(2,2),(-1,-1)' # box '(1,1),(-2,-2)' - (1,1),(-1,-1) - - - - - - geometric_type ## geometric_type - point - - - Computes the closest point to the first object on the second object. - Available for these pairs of types: - (point, box), - (point, lseg), - (point, line), - (lseg, box), - (lseg, lseg), - (line, lseg). - - - point '(0,0)' ## lseg '[(2,0),(0,2)]' - (1,1) - - - - - - geometric_type <-> geometric_type - double precision - - - Computes the distance between the objects. - Available for all seven geometric types, for all combinations - of point with another geometric type, and for - these additional pairs of types: - (box, lseg), - (lseg, line), - (polygon, circle) - (and the commutator cases). - - - circle '<(0,0),1>' <-> circle '<(5,0),1>' - 3 - - - - - - geometric_type @> geometric_type - boolean - - - Does first object contain second? - Available for these pairs of types: - (box, point), - (box, box), - (path, point), - (polygon, point), - (polygon, polygon), - (circle, point), - (circle, circle). - - - circle '<(0,0),2>' @> point '(1,1)' - t - - - - - - geometric_type <@ geometric_type - boolean - - - Is first object contained in or on second? - Available for these pairs of types: - (point, box), - (point, lseg), - (point, line), - (point, path), - (point, polygon), - (point, circle), - (box, box), - (lseg, box), - (lseg, line), - (polygon, polygon), - (circle, circle). - - - point '(1,1)' <@ circle '<(0,0),2>' - t - - - - - - geometric_type && geometric_type - boolean - - - Do these objects overlap? (One point in common makes this true.) - Available for box, polygon, - circle. - - - box '(1,1),(0,0)' && box '(2,2),(0,0)' - t - - - - - - geometric_type << geometric_type - boolean - - - Is first object strictly left of second? - Available for point, box, - polygon, circle. - - - circle '<(0,0),1>' << circle '<(5,0),1>' - t - - - - - - geometric_type >> geometric_type - boolean - - - Is first object strictly right of second? - Available for point, box, - polygon, circle. - - - circle '<(5,0),1>' >> circle '<(0,0),1>' - t - - - - - - geometric_type &< geometric_type - boolean - - - Does first object not extend to the right of second? - Available for box, polygon, - circle. - - - box '(1,1),(0,0)' &< box '(2,2),(0,0)' - t - - - - - - geometric_type &> geometric_type - boolean - - - Does first object not extend to the left of second? - Available for box, polygon, - circle. - - - box '(3,3),(0,0)' &> box '(2,2),(0,0)' - t - - - - - - geometric_type <<| geometric_type - boolean - - - Is first object strictly below second? - Available for point, box, polygon, - circle. - - - box '(3,3),(0,0)' <<| box '(5,5),(3,4)' - t - - - - - - geometric_type |>> geometric_type - boolean - - - Is first object strictly above second? - Available for point, box, polygon, - circle. - - - box '(5,5),(3,4)' |>> box '(3,3),(0,0)' - t - - - - - - geometric_type &<| geometric_type - boolean - - - Does first object not extend above second? - Available for box, polygon, - circle. - - - box '(1,1),(0,0)' &<| box '(2,2),(0,0)' - t - - - - - - geometric_type |&> geometric_type - boolean - - - Does first object not extend below second? - Available for box, polygon, - circle. - - - box '(3,3),(0,0)' |&> box '(2,2),(0,0)' - t - - - - - - box <^ box - boolean - - - Is first object below second (allows edges to touch)? - - - box '((1,1),(0,0))' <^ box '((2,2),(1,1))' - t - - - - - - box >^ box - boolean - - - Is first object above second (allows edges to touch)? - - - box '((2,2),(1,1))' >^ box '((1,1),(0,0))' - t - - - - - - geometric_type ?# geometric_type - boolean - - - Do these objects intersect? - Available for these pairs of types: - (box, box), - (lseg, box), - (lseg, lseg), - (lseg, line), - (line, box), - (line, line), - (path, path). - - - lseg '[(-1,0),(1,0)]' ?# box '(2,2),(-2,-2)' - t - - - - - - ?- line - boolean - - - ?- lseg - boolean - - - Is line horizontal? - - - ?- lseg '[(-1,0),(1,0)]' - t - - - - - - point ?- point - boolean - - - Are points horizontally aligned (that is, have same y coordinate)? - - - point '(1,0)' ?- point '(0,0)' - t - - - - - - ?| line - boolean - - - ?| lseg - boolean - - - Is line vertical? - - - ?| lseg '[(-1,0),(1,0)]' - f - - - - - - point ?| point - boolean - - - Are points vertically aligned (that is, have same x coordinate)? - - - point '(0,1)' ?| point '(0,0)' - t - - - - - - line ?-| line - boolean - - - lseg ?-| lseg - boolean - - - Are lines perpendicular? - - - lseg '[(0,0),(0,1)]' ?-| lseg '[(0,0),(1,0)]' - t - - - - - - line ?|| line - boolean - - - lseg ?|| lseg - boolean - - - Are lines parallel? - - - lseg '[(-1,0),(1,0)]' ?|| lseg '[(-1,2),(1,2)]' - t - - - - - - geometric_type ~= geometric_type - boolean - - - Are these objects the same? - Available for point, box, - polygon, circle. - - - polygon '((0,0),(1,1))' ~= polygon '((1,1),(0,0))' - t - - - - -

- - - - Note that the same as operator, ~=, - represents the usual notion of equality for the point, - box, polygon, and circle types. - Some of the geometric types also have an = operator, but - = compares for equal areas only. - The other scalar comparison operators (<= and so - on), where available for these types, likewise compare areas. - - - - - - Before PostgreSQL 14, the point - is strictly below/above comparison operators point - <<| point and point - |>> point were respectively - called <^ and >^. These - names are still available, but are deprecated and will eventually be - removed. - - - - - Geometric Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - area - - area ( geometric_type ) - double precision - - - Computes area. - Available for box, path, circle. - A path input must be closed, else NULL is returned. - Also, if the path is self-intersecting, the result may be - meaningless. - - - area(box '(2,2),(0,0)') - 4 - - - - - - - center - - center ( geometric_type ) - point - - - Computes center point. - Available for box, circle. - - - center(box '(1,2),(0,0)') - (0.5,1) - - - - - - - diagonal - - diagonal ( box ) - lseg - - - Extracts box's diagonal as a line segment - (same as lseg(box)). - - - diagonal(box '(1,2),(0,0)') - [(1,2),(0,0)] - - - - - - - diameter - - diameter ( circle ) - double precision - - - Computes diameter of circle. - - - diameter(circle '<(0,0),2>') - 4 - - - - - - - height - - height ( box ) - double precision - - - Computes vertical size of box. - - - height(box '(1,2),(0,0)') - 2 - - - - - - - isclosed - - isclosed ( path ) - boolean - - - Is path closed? - - - isclosed(path '((0,0),(1,1),(2,0))') - t - - - - - - - isopen - - isopen ( path ) - boolean - - - Is path open? - - - isopen(path '[(0,0),(1,1),(2,0)]') - t - - - - - - - length - - length ( geometric_type ) - double precision - - - Computes the total length. - Available for lseg, path. - - - length(path '((-1,0),(1,0))') - 4 - - - - - - - npoints - - npoints ( geometric_type ) - integer - - - Returns the number of points. - Available for path, polygon. - - - npoints(path '[(0,0),(1,1),(2,0)]') - 3 - - - - - - - pclose - - pclose ( path ) - path - - - Converts path to closed form. - - - pclose(path '[(0,0),(1,1),(2,0)]') - ((0,0),(1,1),(2,0)) - - - - - - - popen - - popen ( path ) - path - - - Converts path to open form. - - - popen(path '((0,0),(1,1),(2,0))') - [(0,0),(1,1),(2,0)] - - - - - - - radius - - radius ( circle ) - double precision - - - Computes radius of circle. - - - radius(circle '<(0,0),2>') - 2 - - - - - - - slope - - slope ( point, point ) - double precision - - - Computes slope of a line drawn through the two points. - - - slope(point '(0,0)', point '(2,1)') - 0.5 - - - - - - - width - - width ( box ) - double precision - - - Computes horizontal size of box. - - - width(box '(1,2),(0,0)') - 1 - - - - -

- - - Geometric Type Conversion Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - box - - box ( circle ) - box - - - Computes box inscribed within the circle. - - - box(circle '<(0,0),2>') - (1.414213562373095,1.414213562373095),&zwsp;(-1.414213562373095,-1.414213562373095) - - - - - - box ( point ) - box - - - Converts point to empty box. - - - box(point '(1,0)') - (1,0),(1,0) - - - - - - box ( point, point ) - box - - - Converts any two corner points to box. - - - box(point '(0,1)', point '(1,0)') - (1,1),(0,0) - - - - - - box ( polygon ) - box - - - Computes bounding box of polygon. - - - box(polygon '((0,0),(1,1),(2,0))') - (2,1),(0,0) - - - - - - - bound_box - - bound_box ( box, box ) - box - - - Computes bounding box of two boxes. - - - bound_box(box '(1,1),(0,0)', box '(4,4),(3,3)') - (4,4),(0,0) - - - - - - - circle - - circle ( box ) - circle - - - Computes smallest circle enclosing box. - - - circle(box '(1,1),(0,0)') - <(0.5,0.5),0.7071067811865476> - - - - - - circle ( point, double precision ) - circle - - - Constructs circle from center and radius. - - - circle(point '(0,0)', 2.0) - <(0,0),2> - - - - - - circle ( polygon ) - circle - - - Converts polygon to circle. The circle's center is the mean of the - positions of the polygon's points, and the radius is the average - distance of the polygon's points from that center. - - - circle(polygon '((0,0),(1,3),(2,0))') - <(1,1),1.6094757082487299> - - - - - - - line - - line ( point, point ) - line - - - Converts two points to the line through them. - - - line(point '(-1,0)', point '(1,0)') - {0,-1,0} - - - - - - - lseg - - lseg ( box ) - lseg - - - Extracts box's diagonal as a line segment. - - - lseg(box '(1,0),(-1,0)') - [(1,0),(-1,0)] - - - - - - lseg ( point, point ) - lseg - - - Constructs line segment from two endpoints. - - - lseg(point '(-1,0)', point '(1,0)') - [(-1,0),(1,0)] - - - - - - - path - - path ( polygon ) - path - - - Converts polygon to a closed path with the same list of points. - - - path(polygon '((0,0),(1,1),(2,0))') - ((0,0),(1,1),(2,0)) - - - - - - - point - - point ( double precision, double precision ) - point - - - Constructs point from its coordinates. - - - point(23.4, -44.5) - (23.4,-44.5) - - - - - - point ( box ) - point - - - Computes center of box. - - - point(box '(1,0),(-1,0)') - (0,0) - - - - - - point ( circle ) - point - - - Computes center of circle. - - - point(circle '<(0,0),2>') - (0,0) - - - - - - point ( lseg ) - point - - - Computes center of line segment. - - - point(lseg '[(-1,0),(1,0)]') - (0,0) - - - - - - point ( polygon ) - point - - - Computes center of polygon (the mean of the - positions of the polygon's points). - - - point(polygon '((0,0),(1,1),(2,0))') - (1,0.3333333333333333) - - - - - - - polygon - - polygon ( box ) - polygon - - - Converts box to a 4-point polygon. - - - polygon(box '(1,1),(0,0)') - ((0,0),(0,1),(1,1),(1,0)) - - - - - - polygon ( circle ) - polygon - - - Converts circle to a 12-point polygon. - - - polygon(circle '<(0,0),2>') - ((-2,0),&zwsp;(-1.7320508075688774,0.9999999999999999),&zwsp;(-1.0000000000000002,1.7320508075688772),&zwsp;(-1.2246063538223773e-16,2),&zwsp;(0.9999999999999996,1.7320508075688774),&zwsp;(1.732050807568877,1.0000000000000007),&zwsp;(2,2.4492127076447545e-16),&zwsp;(1.7320508075688776,-0.9999999999999994),&zwsp;(1.0000000000000009,-1.7320508075688767),&zwsp;(3.673819061467132e-16,-2),&zwsp;(-0.9999999999999987,-1.732050807568878),&zwsp;(-1.7320508075688767,-1.0000000000000009)) - - - - - - polygon ( integer, circle ) - polygon - - - Converts circle to an n-point polygon. - - - polygon(4, circle '<(3,0),1>') - ((2,0),&zwsp;(3,1),&zwsp;(4,1.2246063538223773e-16),&zwsp;(3,-1)) - - - - - - polygon ( path ) - polygon - - - Converts closed path to a polygon with the same list of points. - - - polygon(path '((0,0),(1,1),(2,0))') - ((0,0),(1,1),(2,0)) - - - - - -

- - - It is possible to access the two component numbers of a point - as though the point were an array with indexes 0 and 1. For example, if - t.p is a point column then - SELECT p[0] FROM t retrieves the X coordinate and - UPDATE t SET p[1] = ... changes the Y coordinate. - In the same way, a value of type box or lseg can be treated - as an array of two point values. - - - - - - - Network Address Functions and Operators - - - The IP network address types, cidr and inet, - support the usual comparison operators shown in - - as well as the specialized operators and functions shown in - and - . - - - - Any cidr value can be cast to inet implicitly; - therefore, the operators and functions shown below as operating on - inet also work on cidr values. (Where there are - separate functions for inet and cidr, it is - because the behavior should be different for the two cases.) - Also, it is permitted to cast an inet value - to cidr. When this is done, any bits to the right of the - netmask are silently zeroed to create a valid cidr value. - - - - IP Address Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - inet << inet - boolean - - - Is subnet strictly contained by subnet? - This operator, and the next four, test for subnet inclusion. They - consider only the network parts of the two addresses (ignoring any - bits to the right of the netmasks) and determine whether one network - is identical to or a subnet of the other. - - - inet '192.168.1.5' << inet '192.168.1/24' - t - - - inet '192.168.0.5' << inet '192.168.1/24' - f - - - inet '192.168.1/24' << inet '192.168.1/24' - f - - - - - - inet <<= inet - boolean - - - Is subnet contained by or equal to subnet? - - - inet '192.168.1/24' <<= inet '192.168.1/24' - t - - - - - - inet >> inet - boolean - - - Does subnet strictly contain subnet? - - - inet '192.168.1/24' >> inet '192.168.1.5' - t - - - - - - inet >>= inet - boolean - - - Does subnet contain or equal subnet? - - - inet '192.168.1/24' >>= inet '192.168.1/24' - t - - - - - - inet && inet - boolean - - - Does either subnet contain or equal the other? - - - inet '192.168.1/24' && inet '192.168.1.80/28' - t - - - inet '192.168.1/24' && inet '192.168.2.0/28' - f - - - - - - ~ inet - inet - - - Computes bitwise NOT. - - - ~ inet '192.168.1.6' - 63.87.254.249 - - - - - - inet & inet - inet - - - Computes bitwise AND. - - - inet '192.168.1.6' & inet '0.0.0.255' - 0.0.0.6 - - - - - - inet | inet - inet - - - Computes bitwise OR. - - - inet '192.168.1.6' | inet '0.0.0.255' - 192.168.1.255 - - - - - - inet + bigint - inet - - - Adds an offset to an address. - - - inet '192.168.1.6' + 25 - 192.168.1.31 - - - - - - bigint + inet - inet - - - Adds an offset to an address. - - - 200 + inet '::ffff:fff0:1' - ::ffff:255.240.0.201 - - - - - - inet - bigint - inet - - - Subtracts an offset from an address. - - - inet '192.168.1.43' - 36 - 192.168.1.7 - - - - - - inet - inet - bigint - - - Computes the difference of two addresses. - - - inet '192.168.1.43' - inet '192.168.1.19' - 24 - - - inet '::1' - inet '::ffff:1' - -4294901760 - - - - -

- - - IP Address Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - abbrev - - abbrev ( inet ) - text - - - Creates an abbreviated display format as text. - (The result is the same as the inet output function - produces; it is abbreviated only in comparison to the - result of an explicit cast to text, which for historical - reasons will never suppress the netmask part.) - - - abbrev(inet '10.1.0.0/32') - 10.1.0.0 - - - - - - abbrev ( cidr ) - text - - - Creates an abbreviated display format as text. - (The abbreviation consists of dropping all-zero octets to the right - of the netmask; more examples are in - .) - - - abbrev(cidr '10.1.0.0/16') - 10.1/16 - - - - - - - broadcast - - broadcast ( inet ) - inet - - - Computes the broadcast address for the address's network. - - - broadcast(inet '192.168.1.5/24') - 192.168.1.255/24 - - - - - - - family - - family ( inet ) - integer - - - Returns the address's family: 4 for IPv4, - 6 for IPv6. - - - family(inet '::1') - 6 - - - - - - - host - - host ( inet ) - text - - - Returns the IP address as text, ignoring the netmask. - - - host(inet '192.168.1.0/24') - 192.168.1.0 - - - - - - - hostmask - - hostmask ( inet ) - inet - - - Computes the host mask for the address's network. - - - hostmask(inet '192.168.23.20/30') - 0.0.0.3 - - - - - - - inet_merge - - inet_merge ( inet, inet ) - cidr - - - Computes the smallest network that includes both of the given networks. - - - inet_merge(inet '192.168.1.5/24', inet '192.168.2.5/24') - 192.168.0.0/22 - - - - - - - inet_same_family - - inet_same_family ( inet, inet ) - boolean - - - Tests whether the addresses belong to the same IP family. - - - inet_same_family(inet '192.168.1.5/24', inet '::1') - f - - - - - - - masklen - - masklen ( inet ) - integer - - - Returns the netmask length in bits. - - - masklen(inet '192.168.1.5/24') - 24 - - - - - - - netmask - - netmask ( inet ) - inet - - - Computes the network mask for the address's network. - - - netmask(inet '192.168.1.5/24') - 255.255.255.0 - - - - - - - network - - network ( inet ) - cidr - - - Returns the network part of the address, zeroing out - whatever is to the right of the netmask. - (This is equivalent to casting the value to cidr.) - - - network(inet '192.168.1.5/24') - 192.168.1.0/24 - - - - - - - set_masklen - - set_masklen ( inet, integer ) - inet - - - Sets the netmask length for an inet value. - The address part does not change. - - - set_masklen(inet '192.168.1.5/24', 16) - 192.168.1.5/16 - - - - - - set_masklen ( cidr, integer ) - cidr - - - Sets the netmask length for a cidr value. - Address bits to the right of the new netmask are set to zero. - - - set_masklen(cidr '192.168.1.0/24', 16) - 192.168.0.0/16 - - - - - - - text - - text ( inet ) - text - - - Returns the unabbreviated IP address and netmask length as text. - (This has the same result as an explicit cast to text.) - - - text(inet '192.168.1.5') - 192.168.1.5/32 - - - - -

- - - - The abbrev, host, - and text functions are primarily intended to offer - alternative display formats for IP addresses. - - - - - The MAC address types, macaddr and macaddr8, - support the usual comparison operators shown in - - as well as the specialized functions shown in - . - In addition, they support the bitwise logical operators - ~, & and | - (NOT, AND and OR), just as shown above for IP addresses. - - - - MAC Address Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - trunc - - trunc ( macaddr ) - macaddr - - - Sets the last 3 bytes of the address to zero. The remaining prefix - can be associated with a particular manufacturer (using data not - included in PostgreSQL). - - - trunc(macaddr '12:34:56:78:90:ab') - 12:34:56:00:00:00 - - - - - - trunc ( macaddr8 ) - macaddr8 - - - Sets the last 5 bytes of the address to zero. The remaining prefix - can be associated with a particular manufacturer (using data not - included in PostgreSQL). - - - trunc(macaddr8 '12:34:56:78:90:ab:cd:ef') - 12:34:56:00:00:00:00:00 - - - - - - - macaddr8_set7bit - - macaddr8_set7bit ( macaddr8 ) - macaddr8 - - - Sets the 7th bit of the address to one, creating what is known as - modified EUI-64, for inclusion in an IPv6 address. - - - macaddr8_set7bit(macaddr8 '00:34:56:ab:cd:ef') - 02:34:56:ff:fe:ab:cd:ef - - - - -

- - - - - - Text Search Functions and Operators - - - full text search - functions and operators - - - - text search - functions and operators - - - - , - and - - summarize the functions and operators that are provided - for full text searching. See for a detailed - explanation of PostgreSQL's text search - facility. - - - - Text Search Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - tsvector @@ tsquery - boolean - - - tsquery @@ tsvector - boolean - - - Does tsvector match tsquery? - (The arguments can be given in either order.) - - - to_tsvector('fat cats ate rats') @@ to_tsquery('cat & rat') - t - - - - - - text @@ tsquery - boolean - - - Does text string, after implicit invocation - of to_tsvector(), match tsquery? - - - 'fat cats ate rats' @@ to_tsquery('cat & rat') - t - - - - - - tsvector || tsvector - tsvector - - - Concatenates two tsvectors. If both inputs contain - lexeme positions, the second input's positions are adjusted - accordingly. - - - 'a:1 b:2'::tsvector || 'c:1 d:2 b:3'::tsvector - 'a':1 'b':2,5 'c':3 'd':4 - - - - - - tsquery && tsquery - tsquery - - - ANDs two tsquerys together, producing a query that - matches documents that match both input queries. - - - 'fat | rat'::tsquery && 'cat'::tsquery - ( 'fat' | 'rat' ) & 'cat' - - - - - - tsquery || tsquery - tsquery - - - ORs two tsquerys together, producing a query that - matches documents that match either input query. - - - 'fat | rat'::tsquery || 'cat'::tsquery - 'fat' | 'rat' | 'cat' - - - - - - !! tsquery - tsquery - - - Negates a tsquery, producing a query that matches - documents that do not match the input query. - - - !! 'cat'::tsquery - !'cat' - - - - - - tsquery <-> tsquery - tsquery - - - Constructs a phrase query, which matches if the two input queries - match at successive lexemes. - - - to_tsquery('fat') <-> to_tsquery('rat') - 'fat' <-> 'rat' - - - - - - tsquery @> tsquery - boolean - - - Does first tsquery contain the second? (This considers - only whether all the lexemes appearing in one query appear in the - other, ignoring the combining operators.) - - - 'cat'::tsquery @> 'cat & rat'::tsquery - f - - - - - - tsquery <@ tsquery - boolean - - - Is first tsquery contained in the second? (This - considers only whether all the lexemes appearing in one query appear - in the other, ignoring the combining operators.) - - - 'cat'::tsquery <@ 'cat & rat'::tsquery - t - - - 'cat'::tsquery <@ '!cat & rat'::tsquery - t - - - - -

- - - In addition to these specialized operators, the usual comparison - operators shown in are - available for types tsvector and tsquery. - These are not very - useful for text searching but allow, for example, unique indexes to be - built on columns of these types. - - - - Text Search Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - array_to_tsvector - - array_to_tsvector ( text[] ) - tsvector - - - Converts an array of text strings to a tsvector. - The given strings are used as lexemes as-is, without further - processing. Array elements must not be empty strings - or NULL. - - - array_to_tsvector('{fat,cat,rat}'::text[]) - 'cat' 'fat' 'rat' - - - - - - - get_current_ts_config - - get_current_ts_config ( ) - regconfig - - - Returns the OID of the current default text search configuration - (as set by ). - - - get_current_ts_config() - english - - - - - - - length - - length ( tsvector ) - integer - - - Returns the number of lexemes in the tsvector. - - - length('fat:2,4 cat:3 rat:5A'::tsvector) - 3 - - - - - - - numnode - - numnode ( tsquery ) - integer - - - Returns the number of lexemes plus operators in - the tsquery. - - - numnode('(fat & rat) | cat'::tsquery) - 5 - - - - - - - plainto_tsquery - - plainto_tsquery ( - config regconfig, - query text ) - tsquery - - - Converts text to a tsquery, normalizing words according to - the specified or default configuration. Any punctuation in the string - is ignored (it does not determine query operators). The resulting - query matches documents containing all non-stopwords in the text. - - - plainto_tsquery('english', 'The Fat Rats') - 'fat' & 'rat' - - - - - - - phraseto_tsquery - - phraseto_tsquery ( - config regconfig, - query text ) - tsquery - - - Converts text to a tsquery, normalizing words according to - the specified or default configuration. Any punctuation in the string - is ignored (it does not determine query operators). The resulting - query matches phrases containing all non-stopwords in the text. - - - phraseto_tsquery('english', 'The Fat Rats') - 'fat' <-> 'rat' - - - phraseto_tsquery('english', 'The Cat and Rats') - 'cat' <2> 'rat' - - - - - - - websearch_to_tsquery - - websearch_to_tsquery ( - config regconfig, - query text ) - tsquery - - - Converts text to a tsquery, normalizing words according - to the specified or default configuration. Quoted word sequences are - converted to phrase tests. The word or is understood - as producing an OR operator, and a dash produces a NOT operator; - other punctuation is ignored. - This approximates the behavior of some common web search tools. - - - websearch_to_tsquery('english', '"fat rat" or cat dog') - 'fat' <-> 'rat' | 'cat' & 'dog' - - - - - - - querytree - - querytree ( tsquery ) - text - - - Produces a representation of the indexable portion of - a tsquery. A result that is empty or - just T indicates a non-indexable query. - - - querytree('foo & ! bar'::tsquery) - 'foo' - - - - - - - setweight - - setweight ( vector tsvector, weight "char" ) - tsvector - - - Assigns the specified weight to each element - of the vector. - - - setweight('fat:2,4 cat:3 rat:5B'::tsvector, 'A') - 'cat':3A 'fat':2A,4A 'rat':5A - - - - - - - setweight - setweight for specific lexeme(s) - - setweight ( vector tsvector, weight "char", lexemes text[] ) - tsvector - - - Assigns the specified weight to elements - of the vector that are listed - in lexemes. - The strings in lexemes are taken as lexemes - as-is, without further processing. Strings that do not match any - lexeme in vector are ignored. - - - setweight('fat:2,4 cat:3 rat:5,6B'::tsvector, 'A', '{cat,rat}') - 'cat':3A 'fat':2,4 'rat':5A,6A - - - - - - - strip - - strip ( tsvector ) - tsvector - - - Removes positions and weights from the tsvector. - - - strip('fat:2,4 cat:3 rat:5A'::tsvector) - 'cat' 'fat' 'rat' - - - - - - - to_tsquery - - to_tsquery ( - config regconfig, - query text ) - tsquery - - - Converts text to a tsquery, normalizing words according to - the specified or default configuration. The words must be combined - by valid tsquery operators. - - - to_tsquery('english', 'The & Fat & Rats') - 'fat' & 'rat' - - - - - - - to_tsvector - - to_tsvector ( - config regconfig, - document text ) - tsvector - - - Converts text to a tsvector, normalizing words according - to the specified or default configuration. Position information is - included in the result. - - - to_tsvector('english', 'The Fat Rats') - 'fat':2 'rat':3 - - - - - - to_tsvector ( - config regconfig, - document json ) - tsvector - - - to_tsvector ( - config regconfig, - document jsonb ) - tsvector - - - Converts each string value in the JSON document to - a tsvector, normalizing words according to the specified - or default configuration. The results are then concatenated in - document order to produce the output. Position information is - generated as though one stopword exists between each pair of string - values. (Beware that document order of the fields of a - JSON object is implementation-dependent when the input - is jsonb; observe the difference in the examples.) - - - to_tsvector('english', '{"aa": "The Fat Rats", "b": "dog"}'::json) - 'dog':5 'fat':2 'rat':3 - - - to_tsvector('english', '{"aa": "The Fat Rats", "b": "dog"}'::jsonb) - 'dog':1 'fat':4 'rat':5 - - - - - - - json_to_tsvector - - json_to_tsvector ( - config regconfig, - document json, - filter jsonb ) - tsvector - - - - jsonb_to_tsvector - - jsonb_to_tsvector ( - config regconfig, - document jsonb, - filter jsonb ) - tsvector - - - Selects each item in the JSON document that is requested by - the filter and converts each one to - a tsvector, normalizing words according to the specified - or default configuration. The results are then concatenated in - document order to produce the output. Position information is - generated as though one stopword exists between each pair of selected - items. (Beware that document order of the fields of a - JSON object is implementation-dependent when the input - is jsonb.) - The filter must be a jsonb - array containing zero or more of these keywords: - "string" (to include all string values), - "numeric" (to include all numeric values), - "boolean" (to include all boolean values), - "key" (to include all keys), or - "all" (to include all the above). - As a special case, the filter can also be a - simple JSON value that is one of these keywords. - - - json_to_tsvector('english', '{"a": "The Fat Rats", "b": 123}'::json, '["string", "numeric"]') - '123':5 'fat':2 'rat':3 - - - json_to_tsvector('english', '{"cat": "The Fat Rats", "dog": 123}'::json, '"all"') - '123':9 'cat':1 'dog':7 'fat':4 'rat':5 - - - - - - - ts_delete - - ts_delete ( vector tsvector, lexeme text ) - tsvector - - - Removes any occurrence of the given lexeme - from the vector. - The lexeme string is treated as a lexeme as-is, - without further processing. - - - ts_delete('fat:2,4 cat:3 rat:5A'::tsvector, 'fat') - 'cat':3 'rat':5A - - - - - - ts_delete ( vector tsvector, lexemes text[] ) - tsvector - - - Removes any occurrences of the lexemes - in lexemes - from the vector. - The strings in lexemes are taken as lexemes - as-is, without further processing. Strings that do not match any - lexeme in vector are ignored. - - - ts_delete('fat:2,4 cat:3 rat:5A'::tsvector, ARRAY['fat','rat']) - 'cat':3 - - - - - - - ts_filter - - ts_filter ( vector tsvector, weights "char"[] ) - tsvector - - - Selects only elements with the given weights - from the vector. - - - ts_filter('fat:2,4 cat:3b,7c rat:5A'::tsvector, '{a,b}') - 'cat':3B 'rat':5A - - - - - - - ts_headline - - ts_headline ( - config regconfig, - document text, - query tsquery - , options text ) - text - - - Displays, in an abbreviated form, the match(es) for - the query in - the document, which must be raw text not - a tsvector. Words in the document are normalized - according to the specified or default configuration before matching to - the query. Use of this function is discussed in - , which also describes the - available options. - - - ts_headline('The fat cat ate the rat.', 'cat') - The fat cat ate the rat. - - - - - - ts_headline ( - config regconfig, - document json, - query tsquery - , options text ) - text - - - ts_headline ( - config regconfig, - document jsonb, - query tsquery - , options text ) - text - - - Displays, in an abbreviated form, match(es) for - the query that occur in string values - within the JSON document. - See for more details. - - - ts_headline('{"cat":"raining cats and dogs"}'::jsonb, 'cat') - {"cat": "raining cats and dogs"} - - - - - - - ts_rank - - ts_rank ( - weights real[], - vector tsvector, - query tsquery - , normalization integer ) - real - - - Computes a score showing how well - the vector matches - the query. See - for details. - - - ts_rank(to_tsvector('raining cats and dogs'), 'cat') - 0.06079271 - - - - - - - ts_rank_cd - - ts_rank_cd ( - weights real[], - vector tsvector, - query tsquery - , normalization integer ) - real - - - Computes a score showing how well - the vector matches - the query, using a cover density - algorithm. See for details. - - - ts_rank_cd(to_tsvector('raining cats and dogs'), 'cat') - 0.1 - - - - - - - ts_rewrite - - ts_rewrite ( query tsquery, - target tsquery, - substitute tsquery ) - tsquery - - - Replaces occurrences of target - with substitute - within the query. - See for details. - - - ts_rewrite('a & b'::tsquery, 'a'::tsquery, 'foo|bar'::tsquery) - 'b' & ( 'foo' | 'bar' ) - - - - - - ts_rewrite ( query tsquery, - select text ) - tsquery - - - Replaces portions of the query according to - target(s) and substitute(s) obtained by executing - a SELECT command. - See for details. - - - SELECT ts_rewrite('a & b'::tsquery, 'SELECT t,s FROM aliases') - 'b' & ( 'foo' | 'bar' ) - - - - - - - tsquery_phrase - - tsquery_phrase ( query1 tsquery, query2 tsquery ) - tsquery - - - Constructs a phrase query that searches - for matches of query1 - and query2 at successive lexemes (same - as <-> operator). - - - tsquery_phrase(to_tsquery('fat'), to_tsquery('cat')) - 'fat' <-> 'cat' - - - - - - tsquery_phrase ( query1 tsquery, query2 tsquery, distance integer ) - tsquery - - - Constructs a phrase query that searches - for matches of query1 and - query2 that occur exactly - distance lexemes apart. - - - tsquery_phrase(to_tsquery('fat'), to_tsquery('cat'), 10) - 'fat' <10> 'cat' - - - - - - - tsvector_to_array - - tsvector_to_array ( tsvector ) - text[] - - - Converts a tsvector to an array of lexemes. - - - tsvector_to_array('fat:2,4 cat:3 rat:5A'::tsvector) - {cat,fat,rat} - - - - - - - unnest - for tsvector - - unnest ( tsvector ) - setof record - ( lexeme text, - positions smallint[], - weights text ) - - - Expands a tsvector into a set of rows, one per lexeme. - - - select * from unnest('cat:3 fat:2,4 rat:5A'::tsvector) - - - lexeme | positions | weights ---------+-----------+--------- - cat | {3} | {D} - fat | {2,4} | {D,D} - rat | {5} | {A} - - - - - -

- - - - All the text search functions that accept an optional regconfig - argument will use the configuration specified by - - when that argument is omitted. - - - - - The functions in - - are listed separately because they are not usually used in everyday text - searching operations. They are primarily helpful for development and - debugging of new text search configurations. - - - - Text Search Debugging Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - ts_debug - - ts_debug ( - config regconfig, - document text ) - setof record - ( alias text, - description text, - token text, - dictionaries regdictionary[], - dictionary regdictionary, - lexemes text[] ) - - - Extracts and normalizes tokens from - the document according to the specified or - default text search configuration, and returns information about how - each token was processed. - See for details. - - - ts_debug('english', 'The Brightest supernovaes') - (asciiword,"Word, all ASCII",The,{english_stem},english_stem,{}) ... - - - - - - - ts_lexize - - ts_lexize ( dict regdictionary, token text ) - text[] - - - Returns an array of replacement lexemes if the input token is known to - the dictionary, or an empty array if the token is known to the - dictionary but it is a stop word, or NULL if it is not a known word. - See for details. - - - ts_lexize('english_stem', 'stars') - {star} - - - - - - - ts_parse - - ts_parse ( parser_name text, - document text ) - setof record - ( tokid integer, - token text ) - - - Extracts tokens from the document using the - named parser. - See for details. - - - ts_parse('default', 'foo - bar') - (1,foo) ... - - - - - - ts_parse ( parser_oid oid, - document text ) - setof record - ( tokid integer, - token text ) - - - Extracts tokens from the document using a - parser specified by OID. - See for details. - - - ts_parse(3722, 'foo - bar') - (1,foo) ... - - - - - - - ts_token_type - - ts_token_type ( parser_name text ) - setof record - ( tokid integer, - alias text, - description text ) - - - Returns a table that describes each type of token the named parser can - recognize. - See for details. - - - ts_token_type('default') - (1,asciiword,"Word, all ASCII") ... - - - - - - ts_token_type ( parser_oid oid ) - setof record - ( tokid integer, - alias text, - description text ) - - - Returns a table that describes each type of token a parser specified - by OID can recognize. - See for details. - - - ts_token_type(3722) - (1,asciiword,"Word, all ASCII") ... - - - - - - - ts_stat - - ts_stat ( sqlquery text - , weights text ) - setof record - ( word text, - ndoc integer, - nentry integer ) - - - Executes the sqlquery, which must return a - single tsvector column, and returns statistics about each - distinct lexeme contained in the data. - See for details. - - - ts_stat('SELECT vector FROM apod') - (foo,10,15) ... - - - - -

- - - - - UUID Functions - - - UUID - generating - - - - gen_random_uuid - - - - uuidv4 - - - - uuidv7 - - - - uuid_extract_timestamp - - - - uuid_extract_version - - - - shows the PostgreSQL - functions that can be used to generate UUIDs. - - - - <acronym>UUID</acronym> Generation Functions - - - - - - Function - - - Description - - - Example(s) - - - - - - - - - - gen_random_uuid - uuid - - - uuidv4 - uuid - - - Generate a version 4 (random) UUID. - - - gen_random_uuid() - 5b30857f-0bfa-48b5-ac0b-5c64e28078d1 - - - uuidv4() - b42410ee-132f-42ee-9e4f-09a6485c95b8 - - - - - - - uuidv7 - ( shift interval ) - uuid - - - Generate a version 7 (time-ordered) UUID. The timestamp is computed using UNIX timestamp - with millisecond precision + sub-millisecond timestamp + random. The optional parameter - shift will shift the computed timestamp by the given interval. - - - uuidv7() - 019535d9-3df7-79fb-b466-fa907fa17f9e - - - - - -

- - - - The module provides additional functions that - implement other standard algorithms for generating UUIDs. - - - - - shows the PostgreSQL - functions that can be used to extract information from UUIDs. - - - - <acronym>UUID</acronym> Extraction Functions - - - - - - Function - - - Description - - - Example(s) - - - - - - - - - - uuid_extract_timestamp - ( uuid ) - timestamp with time zone - - - Extracts a timestamp with time zone from UUID - version 1 and 7. For other versions, this function returns null. Note that - the extracted timestamp is not necessarily exactly equal to the time the - UUID was generated; this depends on the implementation that generated the - UUID. - - - uuid_extract_timestamp('019535d9-3df7-79fb-b466-&zwsp;fa907fa17f9e'::uuid) - 2025-02-23 21:46:24.503-05 - - - - - - - uuid_extract_version - ( uuid ) - smallint - - - Extracts the version from a UUID of the variant described by - RFC 9562. For - other variants, this function returns null. For example, for a UUID - generated by gen_random_uuid, this function will - return 4. - - - uuid_extract_version('41db1265-8bc1-4ab3-992f-&zwsp;885799a4af1d'::uuid) - 4 - - - uuid_extract_version('019535d9-3df7-79fb-b466-&zwsp;fa907fa17f9e'::uuid) - 7 - - - - - -

- - - PostgreSQL also provides the usual comparison - operators shown in for - UUIDs. - - - See for details on the data type - uuid in PostgreSQL. - - - - - - XML Functions - - - XML Functions - - - - The functions and function-like expressions described in this - section operate on values of type xml. See for information about the xml - type. The function-like expressions xmlparse - and xmlserialize for converting to and from - type xml are documented there, not in this section. - - - - Use of most of these functions - requires PostgreSQL to have been built - with configure --with-libxml. - - - - Producing XML Content - - - A set of functions and function-like expressions is available for - producing XML content from SQL data. As such, they are - particularly suitable for formatting query results into XML - documents for processing in client applications. - - - - <literal>xmltext</literal> - - - xmltext - - - -xmltext ( text ) xml - - - - The function xmltext returns an XML value with a single - text node containing the input argument as its content. Predefined entities - like ampersand (), left and right angle brackets - (]]>), and quotation marks () - are escaped. - - - - Example: -'); - xmltext -------------------------- - < foo & bar > -]]> - - - - - <literal>xmlcomment</literal> - - - xmlcomment - - - -xmlcomment ( text ) xml - - - - The function xmlcomment creates an XML value - containing an XML comment with the specified text as content. - The text cannot contain -- or end with a - -, otherwise the resulting construct - would not be a valid XML comment. - If the argument is null, the result is null. - - - - Example: - -]]> - - - - - <literal>xmlconcat</literal> - - - xmlconcat - - - -xmlconcat ( xml , ... ) xml - - - - The function xmlconcat concatenates a list - of individual XML values to create a single value containing an - XML content fragment. Null values are omitted; the result is - only null if there are no nonnull arguments. - - - - Example: -', 'foo'); - - xmlconcat ----------------------- - foo -]]> - - - - XML declarations, if present, are combined as follows. If all - argument values have the same XML version declaration, that - version is used in the result, else no version is used. If all - argument values have the standalone declaration value - yes, then that value is used in the result. If - all argument values have a standalone declaration value and at - least one is no, then that is used in the result. - Else the result will have no standalone declaration. If the - result is determined to require a standalone declaration but no - version declaration, a version declaration with version 1.0 will - be used because XML requires an XML declaration to contain a - version declaration. Encoding declarations are ignored and - removed in all cases. - - - - Example: -', ''); - - xmlconcat ------------------------------------ - -]]> - - - - - <literal>xmlelement</literal> - - - xmlelement - - - -xmlelement ( NAME name , XMLATTRIBUTES ( attvalue AS attname , ... ) , content , ... ) xml - - - - The xmlelement expression produces an XML - element with the given name, attributes, and content. - The name - and attname items shown in the syntax are - simple identifiers, not values. The attvalue - and content items are expressions, which can - yield any PostgreSQL data type. The - argument(s) within XMLATTRIBUTES generate attributes - of the XML element; the content value(s) are - concatenated to form its content. - - - - Examples: - - -SELECT xmlelement(name foo, xmlattributes('xyz' as bar)); - - xmlelement ------------------- - - -SELECT xmlelement(name foo, xmlattributes(current_date as bar), 'cont', 'ent'); - - xmlelement -------------------------------------- - content -]]> - - - - Element and attribute names that are not valid XML names are - escaped by replacing the offending characters by the sequence - _xHHHH_, where - HHHH is the character's Unicode - codepoint in hexadecimal notation. For example: - -]]> - - - - An explicit attribute name need not be specified if the attribute - value is a column reference, in which case the column's name will - be used as the attribute name by default. In other cases, the - attribute must be given an explicit name. So this example is - valid: - -CREATE TABLE test (a xml, b xml); -SELECT xmlelement(name test, xmlattributes(a, b)) FROM test; - - But these are not: - -SELECT xmlelement(name test, xmlattributes('constant'), a, b) FROM test; -SELECT xmlelement(name test, xmlattributes(func(a, b))) FROM test; - - - - - Element content, if specified, will be formatted according to - its data type. If the content is itself of type xml, - complex XML documents can be constructed. For example: - -]]> - - Content of other types will be formatted into valid XML character - data. This means in particular that the characters <, >, - and & will be converted to entities. Binary data (data type - bytea) will be represented in base64 or hex - encoding, depending on the setting of the configuration parameter - . The particular behavior for - individual data types is expected to evolve in order to align the - PostgreSQL mappings with those specified in SQL:2006 and later, - as discussed in . - - - - - <literal>xmlforest</literal> - - - xmlforest - - - -xmlforest ( content AS name , ... ) xml - - - - The xmlforest expression produces an XML - forest (sequence) of elements using the given names and content. - As for xmlelement, - each name must be a simple identifier, while - the content expressions can have any data - type. - - - - Examples: - -SELECT xmlforest('abc' AS foo, 123 AS bar); - - xmlforest ------------------------------- - <foo>abc</foo><bar>123</bar> - - -SELECT xmlforest(table_name, column_name) -FROM information_schema.columns -WHERE table_schema = 'pg_catalog'; - - xmlforest -------------------------------------&zwsp;----------------------------------- - <table_name>pg_authid</table_name>&zwsp;<column_name>rolname</column_name> - <table_name>pg_authid</table_name>&zwsp;<column_name>rolsuper</column_name> - ... - - - As seen in the second example, the element name can be omitted if - the content value is a column reference, in which case the column - name is used by default. Otherwise, a name must be specified. - - - - Element names that are not valid XML names are escaped as shown - for xmlelement above. Similarly, content - data is escaped to make valid XML content, unless it is already - of type xml. - - - - Note that XML forests are not valid XML documents if they consist - of more than one element, so it might be useful to wrap - xmlforest expressions in - xmlelement. - - - - - <literal>xmlpi</literal> - - - xmlpi - - - -xmlpi ( NAME name , content ) xml - - - - The xmlpi expression creates an XML - processing instruction. - As for xmlelement, - the name must be a simple identifier, while - the content expression can have any data type. - The content, if present, must not contain the - character sequence ?>. - - - - Example: - -]]> - - - - - <literal>xmlroot</literal> - - - xmlroot - - - -xmlroot ( xml, VERSION {text|NO VALUE} , STANDALONE {YES|NO|NO VALUE} ) xml - - - - The xmlroot expression alters the properties - of the root node of an XML value. If a version is specified, - it replaces the value in the root node's version declaration; if a - standalone setting is specified, it replaces the value in the - root node's standalone declaration. - - - -abc'), - version '1.0', standalone yes); - - xmlroot ----------------------------------------- - - abc -]]> - - - - - <literal>xmlagg</literal> - - - xmlagg - - - -xmlagg ( xml ) xml - - - - The function xmlagg is, unlike the other - functions described here, an aggregate function. It concatenates the - input values to the aggregate function call, - much like xmlconcat does, except that concatenation - occurs across rows rather than across expressions in a single row. - See for additional information - about aggregate functions. - - - - Example: -abc'); -INSERT INTO test VALUES (2, ''); -SELECT xmlagg(x) FROM test; - xmlagg ----------------------- - abc -]]> - - - - To determine the order of the concatenation, an ORDER BY - clause may be added to the aggregate call as described in - . For example: - -abc -]]> - - - - The following non-standard approach used to be recommended - in previous versions, and may still be useful in specific - cases: - -abc -]]> - - - - - - XML Predicates - - - The expressions described in this section check properties - of xml values. - - - - <literal>IS DOCUMENT</literal> - - - IS DOCUMENT - - - -xml IS DOCUMENT boolean - - - - The expression IS DOCUMENT returns true if the - argument XML value is a proper XML document, false if it is not - (that is, it is a content fragment), or null if the argument is - null. See about the difference - between documents and content fragments. - - - - - <literal>IS NOT DOCUMENT</literal> - - - IS NOT DOCUMENT - - - -xml IS NOT DOCUMENT boolean - - - - The expression IS NOT DOCUMENT returns false if the - argument XML value is a proper XML document, true if it is not (that is, - it is a content fragment), or null if the argument is null. - - - - - <literal>XMLEXISTS</literal> - - - XMLEXISTS - - - -XMLEXISTS ( text PASSING BY {REF|VALUE} xml BY {REF|VALUE} ) boolean - - - - The function xmlexists evaluates an XPath 1.0 - expression (the first argument), with the passed XML value as its context - item. The function returns false if the result of that evaluation - yields an empty node-set, true if it yields any other value. The - function returns null if any argument is null. A nonnull value - passed as the context item must be an XML document, not a content - fragment or any non-XML value. - - - - Example: - TorontoOttawa'); - - xmlexists ------------- - t -(1 row) -]]> - - - - The BY REF and BY VALUE clauses - are accepted in PostgreSQL, but are ignored, - as discussed in . - - - - In the SQL standard, the xmlexists function - evaluates an expression in the XML Query language, - but PostgreSQL allows only an XPath 1.0 - expression, as discussed in - . - - - - - <literal>xml_is_well_formed</literal> - - - xml_is_well_formed - - - - xml_is_well_formed_document - - - - xml_is_well_formed_content - - - -xml_is_well_formed ( text ) boolean -xml_is_well_formed_document ( text ) boolean -xml_is_well_formed_content ( text ) boolean - - - - These functions check whether a text string represents - well-formed XML, returning a Boolean result. - xml_is_well_formed_document checks for a well-formed - document, while xml_is_well_formed_content checks - for well-formed content. xml_is_well_formed does - the former if the configuration - parameter is set to DOCUMENT, or the latter if it is set to - CONTENT. This means that - xml_is_well_formed is useful for seeing whether - a simple cast to type xml will succeed, whereas the other two - functions are useful for seeing whether the corresponding variants of - XMLPARSE will succeed. - - - - Examples: - -'); - xml_is_well_formed --------------------- - f -(1 row) - -SELECT xml_is_well_formed(''); - xml_is_well_formed --------------------- - t -(1 row) - -SET xmloption TO CONTENT; -SELECT xml_is_well_formed('abc'); - xml_is_well_formed --------------------- - t -(1 row) - -SELECT xml_is_well_formed_document('bar'); - xml_is_well_formed_document ------------------------------ - t -(1 row) - -SELECT xml_is_well_formed_document('bar'); - xml_is_well_formed_document ------------------------------ - f -(1 row) -]]> - - The last example shows that the checks include whether - namespaces are correctly matched. - - - - - - Processing XML - - - To process values of data type xml, PostgreSQL offers - the functions xpath and - xpath_exists, which evaluate XPath 1.0 - expressions, and the XMLTABLE - table function. - - - - <literal>xpath</literal> - - - XPath - - - -xpath ( xpath text, xml xml , nsarray text[] ) xml[] - - - - The function xpath evaluates the XPath 1.0 - expression xpath (given as text) - against the XML value - xml. It returns an array of XML values - corresponding to the node-set produced by the XPath expression. - If the XPath expression returns a scalar value rather than a node-set, - a single-element array is returned. - - - - The second argument must be a well formed XML document. In particular, - it must have a single root node element. - - - - The optional third argument of the function is an array of namespace - mappings. This array should be a two-dimensional text array with - the length of the second axis being equal to 2 (i.e., it should be an - array of arrays, each of which consists of exactly 2 elements). - The first element of each array entry is the namespace name (alias), the - second the namespace URI. It is not required that aliases provided in - this array be the same as those being used in the XML document itself (in - other words, both in the XML document and in the xpath - function context, aliases are local). - - - - Example: -test', - ARRAY[ARRAY['my', 'http://example.com']]); - - xpath --------- - {test} -(1 row) -]]> - - - - To deal with default (anonymous) namespaces, do something like this: -test', - ARRAY[ARRAY['mydefns', 'http://example.com']]); - - xpath --------- - {test} -(1 row) -]]> - - - - - <literal>xpath_exists</literal> - - - xpath_exists - - - -xpath_exists ( xpath text, xml xml , nsarray text[] ) boolean - - - - The function xpath_exists is a specialized form - of the xpath function. Instead of returning the - individual XML values that satisfy the XPath 1.0 expression, this function - returns a Boolean indicating whether the query was satisfied or not - (specifically, whether it produced any value other than an empty node-set). - This function is equivalent to the XMLEXISTS predicate, - except that it also offers support for a namespace mapping argument. - - - - Example: -test', - ARRAY[ARRAY['my', 'http://example.com']]); - - xpath_exists --------------- - t -(1 row) -]]> - - - - - <literal>xmltable</literal> - - - xmltable - - - - table function - XMLTABLE - - - -XMLTABLE ( - XMLNAMESPACES ( namespace_uri AS namespace_name , ... ), - row_expression PASSING BY {REF|VALUE} document_expression BY {REF|VALUE} - COLUMNS name { type PATH column_expression DEFAULT default_expression NOT NULL | NULL - | FOR ORDINALITY } - , ... -) setof record - - - - The xmltable expression produces a table based - on an XML value, an XPath filter to extract rows, and a - set of column definitions. - Although it syntactically resembles a function, it can only appear - as a table in a query's FROM clause. - - - - The optional XMLNAMESPACES clause gives a - comma-separated list of namespace definitions, where - each namespace_uri is a text - expression and each namespace_name is a simple - identifier. It specifies the XML namespaces used in the document and - their aliases. A default namespace specification is not currently - supported. - - - - The required row_expression argument is an - XPath 1.0 expression (given as text) that is evaluated, - passing the XML value document_expression as - its context item, to obtain a set of XML nodes. These nodes are what - xmltable transforms into output rows. No rows - will be produced if the document_expression - is null, nor if the row_expression produces - an empty node-set or any value other than a node-set. - - - - document_expression provides the context - item for the row_expression. It must be a - well-formed XML document; fragments/forests are not accepted. - The BY REF and BY VALUE clauses - are accepted but ignored, as discussed in - . - - - - In the SQL standard, the xmltable function - evaluates expressions in the XML Query language, - but PostgreSQL allows only XPath 1.0 - expressions, as discussed in - . - - - - The required COLUMNS clause specifies the - column(s) that will be produced in the output table. - See the syntax summary above for the format. - A name is required for each column, as is a data type - (unless FOR ORDINALITY is specified, in which case - type integer is implicit). The path, default and - nullability clauses are optional. - - - - A column marked FOR ORDINALITY will be populated - with row numbers, starting with 1, in the order of nodes retrieved from - the row_expression's result node-set. - At most one column may be marked FOR ORDINALITY. - - - - - XPath 1.0 does not specify an order for nodes in a node-set, so code - that relies on a particular order of the results will be - implementation-dependent. Details can be found in - . - - - - - The column_expression for a column is an - XPath 1.0 expression that is evaluated for each row, with the current - node from the row_expression result as its - context item, to find the value of the column. If - no column_expression is given, then the - column name is used as an implicit path. - - - - If a column's XPath expression returns a non-XML value (which is limited - to string, boolean, or double in XPath 1.0) and the column has a - PostgreSQL type other than xml, the column will be set - as if by assigning the value's string representation to the PostgreSQL - type. (If the value is a boolean, its string representation is taken - to be 1 or 0 if the output - column's type category is numeric, otherwise true or - false.) - - - - If a column's XPath expression returns a non-empty set of XML nodes - and the column's PostgreSQL type is xml, the column will - be assigned the expression result exactly, if it is of document or - content form. - - - A result containing more than one element node at the top level, or - non-whitespace text outside of an element, is an example of content form. - An XPath result can be of neither form, for example if it returns an - attribute node selected from the element that contains it. Such a result - will be put into content form with each such disallowed node replaced by - its string value, as defined for the XPath 1.0 - string function. - - - - - - A non-XML result assigned to an xml output column produces - content, a single text node with the string value of the result. - An XML result assigned to a column of any other type may not have more than - one node, or an error is raised. If there is exactly one node, the column - will be set as if by assigning the node's string - value (as defined for the XPath 1.0 string function) - to the PostgreSQL type. - - - - The string value of an XML element is the concatenation, in document order, - of all text nodes contained in that element and its descendants. The string - value of an element with no descendant text nodes is an - empty string (not NULL). - Any xsi:nil attributes are ignored. - Note that the whitespace-only text() node between two non-text - elements is preserved, and that leading whitespace on a text() - node is not flattened. - The XPath 1.0 string function may be consulted for the - rules defining the string value of other XML node types and non-XML values. - - - - The conversion rules presented here are not exactly those of the SQL - standard, as discussed in . - - - - If the path expression returns an empty node-set - (typically, when it does not match) - for a given row, the column will be set to NULL, unless - a default_expression is specified; then the - value resulting from evaluating that expression is used. - - - - A default_expression, rather than being - evaluated immediately when xmltable is called, - is evaluated each time a default is needed for the column. - If the expression qualifies as stable or immutable, the repeat - evaluation may be skipped. - This means that you can usefully use volatile functions like - nextval in - default_expression. - - - - Columns may be marked NOT NULL. If the - column_expression for a NOT - NULL column does not match anything and there is - no DEFAULT or - the default_expression also evaluates to null, - an error is reported. - - - - Examples: - - - AU - Australia - - - JP - Japan - Shinzo Abe - 145935 - - - SG - Singapore - 697 - - -$$ AS data; - -SELECT xmltable.* - FROM xmldata, - XMLTABLE('//ROWS/ROW' - PASSING data - COLUMNS id int PATH '@id', - ordinality FOR ORDINALITY, - "COUNTRY_NAME" text, - country_id text PATH 'COUNTRY_ID', - size_sq_km float PATH 'SIZE[@unit = "sq_km"]', - size_other text PATH - 'concat(SIZE[@unit!="sq_km"], " ", SIZE[@unit!="sq_km"]/@unit)', - premier_name text PATH 'PREMIER_NAME' DEFAULT 'not specified'); - - id | ordinality | COUNTRY_NAME | country_id | size_sq_km | size_other | premier_name -----+------------+--------------+------------+------------+--------------+--------------- - 1 | 1 | Australia | AU | | | not specified - 5 | 2 | Japan | JP | | 145935 sq_mi | Shinzo Abe - 6 | 3 | Singapore | SG | 697 | | not specified -]]> - - The following example shows concatenation of multiple text() nodes, - usage of the column name as XPath filter, and the treatment of whitespace, - XML comments and processing instructions: - - - Hello2a2 bbbxxxCC - -$$ AS data; - -SELECT xmltable.* - FROM xmlelements, XMLTABLE('/root' PASSING data COLUMNS element text); - element -------------------------- - Hello2a2 bbbxxxCC -]]> - - - - The following example illustrates how - the XMLNAMESPACES clause can be used to specify - a list of namespaces - used in the XML document as well as in the XPath expressions: - - - - - -'::xml) -) -SELECT xmltable.* - FROM XMLTABLE(XMLNAMESPACES('http://example.com/myns' AS x, - 'http://example.com/b' AS "B"), - '/x:example/x:item' - PASSING (SELECT data FROM xmldata) - COLUMNS foo int PATH '@foo', - bar int PATH '@B:bar'); - foo | bar ------+----- - 1 | 2 - 3 | 4 - 4 | 5 -(3 rows) -]]> - - - - - - Mapping Tables to XML - - - XML export - - - - The following functions map the contents of relational tables to - XML values. They can be thought of as XML export functionality: - -table_to_xml ( table regclass, nulls boolean, - tableforest boolean, targetns text ) xml -query_to_xml ( query text, nulls boolean, - tableforest boolean, targetns text ) xml -cursor_to_xml ( cursor refcursor, count integer, nulls boolean, - tableforest boolean, targetns text ) xml - - - - - table_to_xml maps the content of the named - table, passed as parameter table. The - regclass type accepts strings identifying tables using the - usual notation, including optional schema qualification and - double quotes (see for details). - query_to_xml executes the - query whose text is passed as parameter - query and maps the result set. - cursor_to_xml fetches the indicated number of - rows from the cursor specified by the parameter - cursor. This variant is recommended if - large tables have to be mapped, because the result value is built - up in memory by each function. - - - - If tableforest is false, then the resulting - XML document looks like this: - - - data - data - - - - ... - - - ... - -]]> - - If tableforest is true, the result is an - XML content fragment that looks like this: - - data - data - - - - ... - - -... -]]> - - If no table name is available, that is, when mapping a query or a - cursor, the string table is used in the first - format, row in the second format. - - - - The choice between these formats is up to the user. The first - format is a proper XML document, which will be important in many - applications. The second format tends to be more useful in the - cursor_to_xml function if the result values are to be - reassembled into one document later on. The functions for - producing XML content discussed above, in particular - xmlelement, can be used to alter the results - to taste. - - - - The data values are mapped in the same way as described for the - function xmlelement above. - - - - The parameter nulls determines whether null - values should be included in the output. If true, null values in - columns are represented as: - -]]> - where xsi is the XML namespace prefix for XML - Schema Instance. An appropriate namespace declaration will be - added to the result value. If false, columns containing null - values are simply omitted from the output. - - - - The parameter targetns specifies the - desired XML namespace of the result. If no particular namespace - is wanted, an empty string should be passed. - - - - The following functions return XML Schema documents describing the - mappings performed by the corresponding functions above: - -table_to_xmlschema ( table regclass, nulls boolean, - tableforest boolean, targetns text ) xml -query_to_xmlschema ( query text, nulls boolean, - tableforest boolean, targetns text ) xml -cursor_to_xmlschema ( cursor refcursor, nulls boolean, - tableforest boolean, targetns text ) xml - - It is essential that the same parameters are passed in order to - obtain matching XML data mappings and XML Schema documents. - - - - The following functions produce XML data mappings and the - corresponding XML Schema in one document (or forest), linked - together. They can be useful where self-contained and - self-describing results are wanted: - -table_to_xml_and_xmlschema ( table regclass, nulls boolean, - tableforest boolean, targetns text ) xml -query_to_xml_and_xmlschema ( query text, nulls boolean, - tableforest boolean, targetns text ) xml - - - - - In addition, the following functions are available to produce - analogous mappings of entire schemas or the entire current - database: - -schema_to_xml ( schema name, nulls boolean, - tableforest boolean, targetns text ) xml -schema_to_xmlschema ( schema name, nulls boolean, - tableforest boolean, targetns text ) xml -schema_to_xml_and_xmlschema ( schema name, nulls boolean, - tableforest boolean, targetns text ) xml - -database_to_xml ( nulls boolean, - tableforest boolean, targetns text ) xml -database_to_xmlschema ( nulls boolean, - tableforest boolean, targetns text ) xml -database_to_xml_and_xmlschema ( nulls boolean, - tableforest boolean, targetns text ) xml - - - These functions ignore tables that are not readable by the current user. - The database-wide functions additionally ignore schemas that the current - user does not have USAGE (lookup) privilege for. - - - - Note that these potentially produce a lot of data, which needs to - be built up in memory. When requesting content mappings of large - schemas or databases, it might be worthwhile to consider mapping the - tables separately instead, possibly even through a cursor. - - - - The result of a schema content mapping looks like this: - - - -table1-mapping - -table2-mapping - -... - -]]> - - where the format of a table mapping depends on the - tableforest parameter as explained above. - - - - The result of a database content mapping looks like this: - - - - - ... - - - - ... - - -... - -]]> - - where the schema mapping is as above. - - - - As an example of using the output produced by these functions, - shows an XSLT stylesheet that - converts the output of - table_to_xml_and_xmlschema to an HTML - document containing a tabular rendition of the table data. In a - similar manner, the results from these functions can be - converted into other XML-based formats. - - - - XSLT Stylesheet for Converting SQL/XML Output to HTML - - - - - - - - - - - - - <xsl:value-of select="name(current())"/> - - - - - - - - - - - - - - - - -

- - - - - -]]> - - - - - - JSON Functions and Operators - - - JSON - functions and operators - - - SQL/JSON - functions and expressions - - - - This section describes: - - - - - functions and operators for processing and creating JSON data - - - - - the SQL/JSON path language - - - - - the SQL/JSON query functions - - - - - - - To provide native support for JSON data types within the SQL environment, - PostgreSQL implements the - SQL/JSON data model. - This model comprises sequences of items. Each item can hold SQL scalar - values, with an additional SQL/JSON null value, and composite data structures - that use JSON arrays and objects. The model is a formalization of the implied - data model in the JSON specification - RFC 7159. - - - - SQL/JSON allows you to handle JSON data alongside regular SQL data, - with transaction support, including: - - - - - Uploading JSON data into the database and storing it in - regular SQL columns as character or binary strings. - - - - - Generating JSON objects and arrays from relational data. - - - - - Querying JSON data using SQL/JSON query functions and - SQL/JSON path language expressions. - - - - - - - To learn more about the SQL/JSON standard, see - . For details on JSON types - supported in PostgreSQL, - see . - - - - Processing and Creating JSON Data - - - shows the operators that - are available for use with JSON data types (see ). - In addition, the usual comparison operators shown in are available for - jsonb, though not for json. The comparison - operators follow the ordering rules for B-tree operations outlined in - . - See also for the aggregate - function json_agg which aggregates record - values as JSON, the aggregate function - json_object_agg which aggregates pairs of values - into a JSON object, and their jsonb equivalents, - jsonb_agg and jsonb_object_agg. - - - - <type>json</type> and <type>jsonb</type> Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - json -> integer - json - - - jsonb -> integer - jsonb - - - Extracts n'th element of JSON array - (array elements are indexed from zero, but negative integers count - from the end). - - - '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -> 2 - {"c":"baz"} - - - '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -> -3 - {"a":"foo"} - - - - - - json -> text - json - - - jsonb -> text - jsonb - - - Extracts JSON object field with the given key. - - - '{"a": {"b":"foo"}}'::json -> 'a' - {"b":"foo"} - - - - - - json ->> integer - text - - - jsonb ->> integer - text - - - Extracts n'th element of JSON array, - as text. - - - '[1,2,3]'::json ->> 2 - 3 - - - - - - json ->> text - text - - - jsonb ->> text - text - - - Extracts JSON object field with the given key, as text. - - - '{"a":1,"b":2}'::json ->> 'b' - 2 - - - - - - json #> text[] - json - - - jsonb #> text[] - jsonb - - - Extracts JSON sub-object at the specified path, where path elements - can be either field keys or array indexes. - - - '{"a": {"b": ["foo","bar"]}}'::json #> '{a,b,1}' - "bar" - - - - - - json #>> text[] - text - - - jsonb #>> text[] - text - - - Extracts JSON sub-object at the specified path as text. - - - '{"a": {"b": ["foo","bar"]}}'::json #>> '{a,b,1}' - bar - - - - -

- - - - The field/element/path extraction operators return NULL, rather than - failing, if the JSON input does not have the right structure to match - the request; for example if no such key or array element exists. - - - - - Some further operators exist only for jsonb, as shown - in . - - describes how these operators can be used to effectively search indexed - jsonb data. - - - - Additional <type>jsonb</type> Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - jsonb @> jsonb - boolean - - - Does the first JSON value contain the second? - (See for details about containment.) - - - '{"a":1, "b":2}'::jsonb @> '{"b":2}'::jsonb - t - - - - - - jsonb <@ jsonb - boolean - - - Is the first JSON value contained in the second? - - - '{"b":2}'::jsonb <@ '{"a":1, "b":2}'::jsonb - t - - - - - - jsonb ? text - boolean - - - Does the text string exist as a top-level key or array element within - the JSON value? - - - '{"a":1, "b":2}'::jsonb ? 'b' - t - - - '["a", "b", "c"]'::jsonb ? 'b' - t - - - - - - jsonb ?| text[] - boolean - - - Do any of the strings in the text array exist as top-level keys or - array elements? - - - '{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'd'] - t - - - - - - jsonb ?& text[] - boolean - - - Do all of the strings in the text array exist as top-level keys or - array elements? - - - '["a", "b", "c"]'::jsonb ?& array['a', 'b'] - t - - - - - - jsonb || jsonb - jsonb - - - Concatenates two jsonb values. - Concatenating two arrays generates an array containing all the - elements of each input. Concatenating two objects generates an - object containing the union of their - keys, taking the second object's value when there are duplicate keys. - All other cases are treated by converting a non-array input into a - single-element array, and then proceeding as for two arrays. - Does not operate recursively: only the top-level array or object - structure is merged. - - - '["a", "b"]'::jsonb || '["a", "d"]'::jsonb - ["a", "b", "a", "d"] - - - '{"a": "b"}'::jsonb || '{"c": "d"}'::jsonb - {"a": "b", "c": "d"} - - - '[1, 2]'::jsonb || '3'::jsonb - [1, 2, 3] - - - '{"a": "b"}'::jsonb || '42'::jsonb - [{"a": "b"}, 42] - - - To append an array to another array as a single entry, wrap it - in an additional layer of array, for example: - - - '[1, 2]'::jsonb || jsonb_build_array('[3, 4]'::jsonb) - [1, 2, [3, 4]] - - - - - - jsonb - text - jsonb - - - Deletes a key (and its value) from a JSON object, or matching string - value(s) from a JSON array. - - - '{"a": "b", "c": "d"}'::jsonb - 'a' - {"c": "d"} - - - '["a", "b", "c", "b"]'::jsonb - 'b' - ["a", "c"] - - - - - - jsonb - text[] - jsonb - - - Deletes all matching keys or array elements from the left operand. - - - '{"a": "b", "c": "d"}'::jsonb - '{a,c}'::text[] - {} - - - - - - jsonb - integer - jsonb - - - Deletes the array element with specified index (negative - integers count from the end). Throws an error if JSON value - is not an array. - - - '["a", "b"]'::jsonb - 1 - ["a"] - - - - - - jsonb #- text[] - jsonb - - - Deletes the field or array element at the specified path, where path - elements can be either field keys or array indexes. - - - '["a", {"b":1}]'::jsonb #- '{1,b}' - ["a", {}] - - - - - - jsonb @? jsonpath - boolean - - - Does JSON path return any item for the specified JSON value? - (This is useful only with SQL-standard JSON path expressions, not - predicate check - expressions, since those always return a value.) - - - '{"a":[1,2,3,4,5]}'::jsonb @? '$.a[*] ? (@ > 2)' - t - - - - - - jsonb @@ jsonpath - boolean - - - Returns the result of a JSON path predicate check for the - specified JSON value. - (This is useful only - with predicate - check expressions, not SQL-standard JSON path expressions, - since it will return NULL if the path result is - not a single boolean value.) - - - '{"a":[1,2,3,4,5]}'::jsonb @@ '$.a[*] > 2' - t - - - - -

- - - - The jsonpath operators @? - and @@ suppress the following errors: missing object - field or array element, unexpected JSON item type, datetime and numeric - errors. The jsonpath-related functions described below can - also be told to suppress these types of errors. This behavior might be - helpful when searching JSON document collections of varying structure. - - - - - shows the functions that are - available for constructing json and jsonb values. - Some functions in this table have a RETURNING clause, - which specifies the data type returned. It must be one of json, - jsonb, bytea, a character string type (text, - char, or varchar), or a type - that can be cast to json. - By default, the json type is returned. - - - - JSON Creation Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - to_json - - to_json ( anyelement ) - json - - - - to_jsonb - - to_jsonb ( anyelement ) - jsonb - - - Converts any SQL value to json or jsonb. - Arrays and composites are converted recursively to arrays and - objects (multidimensional arrays become arrays of arrays in JSON). - Otherwise, if there is a cast from the SQL data type - to json, the cast function will be used to perform the - conversion; - - For example, the extension has a cast - from hstore to json, so that - hstore values converted via the JSON creation functions - will be represented as JSON objects, not as primitive string values. - - - otherwise, a scalar JSON value is produced. For any scalar other than - a number, a Boolean, or a null value, the text representation will be - used, with escaping as necessary to make it a valid JSON string value. - - - to_json('Fred said "Hi."'::text) - "Fred said \"Hi.\"" - - - to_jsonb(row(42, 'Fred said "Hi."'::text)) - {"f1": 42, "f2": "Fred said \"Hi.\""} - - - - - - - array_to_json - - array_to_json ( anyarray , boolean ) - json - - - Converts an SQL array to a JSON array. The behavior is the same - as to_json except that line feeds will be added - between top-level array elements if the optional boolean parameter is - true. - - - array_to_json('{{1,5},{99,100}}'::int[]) - [[1,5],[99,100]] - - - - - - - json_array - json_array ( - { value_expression FORMAT JSON } , ... - { NULL | ABSENT } ON NULL - RETURNING data_type FORMAT JSON ENCODING UTF8 ) - - - json_array ( - query_expression - RETURNING data_type FORMAT JSON ENCODING UTF8 ) - - - Constructs a JSON array from either a series of - value_expression parameters or from the results - of query_expression, - which must be a SELECT query returning a single column. If - ABSENT ON NULL is specified, NULL values are ignored. - This is always the case if a - query_expression is used. - - - json_array(1,true,json '{"a":null}') - [1, true, {"a":null}] - - - json_array(SELECT * FROM (VALUES(1),(2)) t) - [1, 2] - - - - - - - row_to_json - - row_to_json ( record , boolean ) - json - - - Converts an SQL composite value to a JSON object. The behavior is the - same as to_json except that line feeds will be - added between top-level elements if the optional boolean parameter is - true. - - - row_to_json(row(1,'foo')) - {"f1":1,"f2":"foo"} - - - - - - - json_build_array - - json_build_array ( VARIADIC "any" ) - json - - - - jsonb_build_array - - jsonb_build_array ( VARIADIC "any" ) - jsonb - - - Builds a possibly-heterogeneously-typed JSON array out of a variadic - argument list. Each argument is converted as - per to_json or to_jsonb. - - - json_build_array(1, 2, 'foo', 4, 5) - [1, 2, "foo", 4, 5] - - - - - - - json_build_object - - json_build_object ( VARIADIC "any" ) - json - - - - jsonb_build_object - - jsonb_build_object ( VARIADIC "any" ) - jsonb - - - Builds a JSON object out of a variadic argument list. By convention, - the argument list consists of alternating keys and values. Key - arguments are coerced to text; value arguments are converted as - per to_json or to_jsonb. - - - json_build_object('foo', 1, 2, row(3,'bar')) - {"foo" : 1, "2" : {"f1":3,"f2":"bar"}} - - - - - - json_object - json_object ( - { key_expression { VALUE | ':' } - value_expression FORMAT JSON ENCODING UTF8 }, ... - { NULL | ABSENT } ON NULL - { WITH | WITHOUT } UNIQUE KEYS - RETURNING data_type FORMAT JSON ENCODING UTF8 ) - - - Constructs a JSON object of all the key/value pairs given, - or an empty object if none are given. - key_expression is a scalar expression - defining the JSON key, which is - converted to the text type. - It cannot be NULL nor can it - belong to a type that has a cast to the json type. - If WITH UNIQUE KEYS is specified, there must not - be any duplicate key_expression. - Any pair for which the value_expression - evaluates to NULL is omitted from the output - if ABSENT ON NULL is specified; - if NULL ON NULL is specified or the clause - omitted, the key is included with value NULL. - - - json_object('code' VALUE 'P123', 'title': 'Jaws') - {"code" : "P123", "title" : "Jaws"} - - - - - - - json_object - - json_object ( text[] ) - json - - - - jsonb_object - - jsonb_object ( text[] ) - jsonb - - - Builds a JSON object out of a text array. The array must have either - exactly one dimension with an even number of members, in which case - they are taken as alternating key/value pairs, or two dimensions - such that each inner array has exactly two elements, which - are taken as a key/value pair. All values are converted to JSON - strings. - - - json_object('{a, 1, b, "def", c, 3.5}') - {"a" : "1", "b" : "def", "c" : "3.5"} - - json_object('{{a, 1}, {b, "def"}, {c, 3.5}}') - {"a" : "1", "b" : "def", "c" : "3.5"} - - - - - - json_object ( keys text[], values text[] ) - json - - - jsonb_object ( keys text[], values text[] ) - jsonb - - - This form of json_object takes keys and values - pairwise from separate text arrays. Otherwise it is identical to - the one-argument form. - - - json_object('{a,b}', '{1,2}') - {"a": "1", "b": "2"} - - - - - - json constructor - json ( - expression - FORMAT JSON ENCODING UTF8 - { WITH | WITHOUT } UNIQUE KEYS ) - json - - - Converts a given expression specified as text or - bytea string (in UTF8 encoding) into a JSON - value. If expression is NULL, an - SQL null value is returned. - If WITH UNIQUE is specified, the - expression must not contain any duplicate - object keys. - - - json('{"a":123, "b":[true,"foo"], "a":"bar"}') - {"a":123, "b":[true,"foo"], "a":"bar"} - - - - - - - json_scalar - json_scalar ( expression ) - - - Converts a given SQL scalar value into a JSON scalar value. - If the input is NULL, an SQL null is returned. If - the input is number or a boolean value, a corresponding JSON number - or boolean value is returned. For any other value, a JSON string is - returned. - - - json_scalar(123.45) - 123.45 - - - json_scalar(CURRENT_TIMESTAMP) - "2022-05-10T10:51:04.62128-04:00" - - - - - - json_serialize ( - expression FORMAT JSON ENCODING UTF8 - RETURNING data_type FORMAT JSON ENCODING UTF8 ) - - - Converts an SQL/JSON expression into a character or binary string. The - expression can be of any JSON type, any - character string type, or bytea in UTF8 encoding. - The returned type used in RETURNING can be any - character string type or bytea. The default is - text. - - - json_serialize('{ "a" : 1 } ' RETURNING bytea) - \x7b20226122203a2031207d20 - - - - -

- - - details SQL/JSON - facilities for testing JSON. - - - - SQL/JSON Testing Functions - - - - - Function signature - - - Description - - - Example(s) - - - - - - - IS JSON - expression IS NOT JSON - { VALUE | SCALAR | ARRAY | OBJECT } - { WITH | WITHOUT } UNIQUE KEYS - - - This predicate tests whether expression can be - parsed as JSON, possibly of a specified type. - If SCALAR or ARRAY or - OBJECT is specified, the - test is whether or not the JSON is of that particular type. If - WITH UNIQUE KEYS is specified, then any object in the - expression is also tested to see if it - has duplicate keys. - - - -SELECT js, - js IS JSON "json?", - js IS JSON SCALAR "scalar?", - js IS JSON OBJECT "object?", - js IS JSON ARRAY "array?" -FROM (VALUES - ('123'), ('"abc"'), ('{"a": "b"}'), ('[1,2]'),('abc')) foo(js); - js | json? | scalar? | object? | array? -------------+-------+---------+---------+-------- - 123 | t | t | f | f - "abc" | t | t | f | f - {"a": "b"} | t | f | t | f - [1,2] | t | f | f | t - abc | f | f | f | f - - - - -SELECT js, - js IS JSON OBJECT "object?", - js IS JSON ARRAY "array?", - js IS JSON ARRAY WITH UNIQUE KEYS "array w. UK?", - js IS JSON ARRAY WITHOUT UNIQUE KEYS "array w/o UK?" -FROM (VALUES ('[{"a":"1"}, - {"b":"2","b":"3"}]')) foo(js); --[ RECORD 1 ]-+-------------------- -js | [{"a":"1"}, + - | {"b":"2","b":"3"}] -object? | f -array? | t -array w. UK? | f -array w/o UK? | t - - - - - -

- - - shows the functions that - are available for processing json and jsonb values. - - - - JSON Processing Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - json_array_elements - - json_array_elements ( json ) - setof json - - - - jsonb_array_elements - - jsonb_array_elements ( jsonb ) - setof jsonb - - - Expands the top-level JSON array into a set of JSON values. - - - select * from json_array_elements('[1,true, [2,false]]') - - - value ------------ - 1 - true - [2,false] - - - - - - - - json_array_elements_text - - json_array_elements_text ( json ) - setof text - - - - jsonb_array_elements_text - - jsonb_array_elements_text ( jsonb ) - setof text - - - Expands the top-level JSON array into a set of text values. - - - select * from json_array_elements_text('["foo", "bar"]') - - - value ------------ - foo - bar - - - - - - - - json_array_length - - json_array_length ( json ) - integer - - - - jsonb_array_length - - jsonb_array_length ( jsonb ) - integer - - - Returns the number of elements in the top-level JSON array. - - - json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]') - 5 - - - jsonb_array_length('[]') - 0 - - - - - - - json_each - - json_each ( json ) - setof record - ( key text, - value json ) - - - - jsonb_each - - jsonb_each ( jsonb ) - setof record - ( key text, - value jsonb ) - - - Expands the top-level JSON object into a set of key/value pairs. - - - select * from json_each('{"a":"foo", "b":"bar"}') - - - key | value ------+------- - a | "foo" - b | "bar" - - - - - - - - json_each_text - - json_each_text ( json ) - setof record - ( key text, - value text ) - - - - jsonb_each_text - - jsonb_each_text ( jsonb ) - setof record - ( key text, - value text ) - - - Expands the top-level JSON object into a set of key/value pairs. - The returned values will be of - type text. - - - select * from json_each_text('{"a":"foo", "b":"bar"}') - - - key | value ------+------- - a | foo - b | bar - - - - - - - - json_extract_path - - json_extract_path ( from_json json, VARIADIC path_elems text[] ) - json - - - - jsonb_extract_path - - jsonb_extract_path ( from_json jsonb, VARIADIC path_elems text[] ) - jsonb - - - Extracts JSON sub-object at the specified path. - (This is functionally equivalent to the #> - operator, but writing the path out as a variadic list can be more - convenient in some cases.) - - - json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6') - "foo" - - - - - - - json_extract_path_text - - json_extract_path_text ( from_json json, VARIADIC path_elems text[] ) - text - - - - jsonb_extract_path_text - - jsonb_extract_path_text ( from_json jsonb, VARIADIC path_elems text[] ) - text - - - Extracts JSON sub-object at the specified path as text. - (This is functionally equivalent to the #>> - operator.) - - - json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6') - foo - - - - - - - json_object_keys - - json_object_keys ( json ) - setof text - - - - jsonb_object_keys - - jsonb_object_keys ( jsonb ) - setof text - - - Returns the set of keys in the top-level JSON object. - - - select * from json_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}}') - - - json_object_keys ------------------- - f1 - f2 - - - - - - - - json_populate_record - - json_populate_record ( base anyelement, from_json json ) - anyelement - - - - jsonb_populate_record - - jsonb_populate_record ( base anyelement, from_json jsonb ) - anyelement - - - Expands the top-level JSON object to a row having the composite type - of the base argument. The JSON object - is scanned for fields whose names match column names of the output row - type, and their values are inserted into those columns of the output. - (Fields that do not correspond to any output column name are ignored.) - In typical use, the value of base is just - NULL, which means that any output columns that do - not match any object field will be filled with nulls. However, - if base isn't NULL then - the values it contains will be used for unmatched columns. - - - To convert a JSON value to the SQL type of an output column, the - following rules are applied in sequence: - - - - A JSON null value is converted to an SQL null in all cases. - - - - - If the output column is of type json - or jsonb, the JSON value is just reproduced exactly. - - - - - If the output column is a composite (row) type, and the JSON value - is a JSON object, the fields of the object are converted to columns - of the output row type by recursive application of these rules. - - - - - Likewise, if the output column is an array type and the JSON value - is a JSON array, the elements of the JSON array are converted to - elements of the output array by recursive application of these - rules. - - - - - Otherwise, if the JSON value is a string, the contents of the - string are fed to the input conversion function for the column's - data type. - - - - - Otherwise, the ordinary text representation of the JSON value is - fed to the input conversion function for the column's data type. - - - - - - While the example below uses a constant JSON value, typical use would - be to reference a json or jsonb column - laterally from another table in the query's FROM - clause. Writing json_populate_record in - the FROM clause is good practice, since all of the - extracted columns are available for use without duplicate function - calls. - - - create type subrowtype as (d int, e text); - create type myrowtype as (a int, b text[], c subrowtype); - - - select * from json_populate_record(null::myrowtype, - '{"a": 1, "b": ["2", "a b"], "c": {"d": 4, "e": "a b c"}, "x": "foo"}') - - - a | b | c ----+-----------+------------- - 1 | {2,"a b"} | (4,"a b c") - - - - - - - - jsonb_populate_record_valid - - jsonb_populate_record_valid ( base anyelement, from_json json ) - boolean - - - Function for testing jsonb_populate_record. Returns - true if the input jsonb_populate_record - would finish without an error for the given input JSON object; that is, it's - valid input, false otherwise. - - - create type jsb_char2 as (a char(2)); - - - select jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aaa"}'); - - - jsonb_populate_record_valid ------------------------------ - f -(1 row) - - - select * from jsonb_populate_record(NULL::jsb_char2, '{"a": "aaa"}') q; - - -ERROR: value too long for type character(2) - - select jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aa"}'); - - - jsonb_populate_record_valid ------------------------------ - t -(1 row) - - - select * from jsonb_populate_record(NULL::jsb_char2, '{"a": "aa"}') q; - - - a ----- - aa -(1 row) - - - - - - - - json_populate_recordset - - json_populate_recordset ( base anyelement, from_json json ) - setof anyelement - - - - jsonb_populate_recordset - - jsonb_populate_recordset ( base anyelement, from_json jsonb ) - setof anyelement - - - Expands the top-level JSON array of objects to a set of rows having - the composite type of the base argument. - Each element of the JSON array is processed as described above - for json[b]_populate_record. - - - create type twoints as (a int, b int); - - - select * from json_populate_recordset(null::twoints, '[{"a":1,"b":2}, {"a":3,"b":4}]') - - - a | b ----+--- - 1 | 2 - 3 | 4 - - - - - - - - json_to_record - - json_to_record ( json ) - record - - - - jsonb_to_record - - jsonb_to_record ( jsonb ) - record - - - Expands the top-level JSON object to a row having the composite type - defined by an AS clause. (As with all functions - returning record, the calling query must explicitly - define the structure of the record with an AS - clause.) The output record is filled from fields of the JSON object, - in the same way as described above - for json[b]_populate_record. Since there is no - input record value, unmatched columns are always filled with nulls. - - - create type myrowtype as (a int, b text); - - - select * from json_to_record('{"a":1,"b":[1,2,3],"c":[1,2,3],"e":"bar","r": {"a": 123, "b": "a b c"}}') as x(a int, b text, c int[], d text, r myrowtype) - - - a | b | c | d | r ----+---------+---------+---+--------------- - 1 | [1,2,3] | {1,2,3} | | (123,"a b c") - - - - - - - - json_to_recordset - - json_to_recordset ( json ) - setof record - - - - jsonb_to_recordset - - jsonb_to_recordset ( jsonb ) - setof record - - - Expands the top-level JSON array of objects to a set of rows having - the composite type defined by an AS clause. (As - with all functions returning record, the calling query - must explicitly define the structure of the record with - an AS clause.) Each element of the JSON array is - processed as described above - for json[b]_populate_record. - - - select * from json_to_recordset('[{"a":1,"b":"foo"}, {"a":"2","c":"bar"}]') as x(a int, b text) - - - a | b ----+----- - 1 | foo - 2 | - - - - - - - - jsonb_set - - jsonb_set ( target jsonb, path text[], new_value jsonb , create_if_missing boolean ) - jsonb - - - Returns target - with the item designated by path - replaced by new_value, or with - new_value added if - create_if_missing is true (which is the - default) and the item designated by path - does not exist. - All earlier steps in the path must exist, or - the target is returned unchanged. - As with the path oriented operators, negative integers that - appear in the path count from the end - of JSON arrays. - If the last path step is an array index that is out of range, - and create_if_missing is true, the new - value is added at the beginning of the array if the index is negative, - or at the end of the array if it is positive. - - - jsonb_set('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', '[2,3,4]', false) - [{"f1": [2, 3, 4], "f2": null}, 2, null, 3] - - - jsonb_set('[{"f1":1,"f2":null},2]', '{0,f3}', '[2,3,4]') - [{"f1": 1, "f2": null, "f3": [2, 3, 4]}, 2] - - - - - - - jsonb_set_lax - - jsonb_set_lax ( target jsonb, path text[], new_value jsonb , create_if_missing boolean , null_value_treatment text ) - jsonb - - - If new_value is not NULL, - behaves identically to jsonb_set. Otherwise behaves - according to the value - of null_value_treatment which must be one - of 'raise_exception', - 'use_json_null', 'delete_key', or - 'return_target'. The default is - 'use_json_null'. - - - jsonb_set_lax('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', null) - [{"f1": null, "f2": null}, 2, null, 3] - - - jsonb_set_lax('[{"f1":99,"f2":null},2]', '{0,f3}', null, true, 'return_target') - [{"f1": 99, "f2": null}, 2] - - - - - - - jsonb_insert - - jsonb_insert ( target jsonb, path text[], new_value jsonb , insert_after boolean ) - jsonb - - - Returns target - with new_value inserted. If the item - designated by the path is an array - element, new_value will be inserted before - that item if insert_after is false (which - is the default), or after it - if insert_after is true. If the item - designated by the path is an object - field, new_value will be inserted only if - the object does not already contain that key. - All earlier steps in the path must exist, or - the target is returned unchanged. - As with the path oriented operators, negative integers that - appear in the path count from the end - of JSON arrays. - If the last path step is an array index that is out of range, the new - value is added at the beginning of the array if the index is negative, - or at the end of the array if it is positive. - - - jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"') - {"a": [0, "new_value", 1, 2]} - - - jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"', true) - {"a": [0, 1, "new_value", 2]} - - - - - - - json_strip_nulls - - json_strip_nulls ( target json ,strip_in_arrays boolean ) - json - - - - jsonb_strip_nulls - - jsonb_strip_nulls ( target jsonb ,strip_in_arrays boolean ) - jsonb - - - Deletes all object fields that have null values from the given JSON - value, recursively. - If strip_in_arrays is true (the default is false), - null array elements are also stripped. - Otherwise they are not stripped. Bare null values are never stripped. - - - json_strip_nulls('[{"f1":1, "f2":null}, 2, null, 3]') - [{"f1":1},2,null,3] - - - jsonb_strip_nulls('[1,2,null,3,4]', true); - [1,2,3,4] - - - - - - - - jsonb_path_exists - - jsonb_path_exists ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - boolean - - - Checks whether the JSON path returns any item for the specified JSON - value. - (This is useful only with SQL-standard JSON path expressions, not - predicate check - expressions, since those always return a value.) - If the vars argument is specified, it must - be a JSON object, and its fields provide named values to be - substituted into the jsonpath expression. - If the silent argument is specified and - is true, the function suppresses the same errors - as the @? and @@ operators do. - - - jsonb_path_exists('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}') - t - - - - - - - jsonb_path_match - - jsonb_path_match ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - boolean - - - Returns the SQL boolean result of a JSON path predicate check - for the specified JSON value. - (This is useful only - with predicate - check expressions, not SQL-standard JSON path expressions, - since it will either fail or return NULL if the - path result is not a single boolean value.) - The optional vars - and silent arguments act the same as - for jsonb_path_exists. - - - jsonb_path_match('{"a":[1,2,3,4,5]}', 'exists($.a[*] ? (@ >= $min && @ <= $max))', '{"min":2, "max":4}') - t - - - - - - - jsonb_path_query - - jsonb_path_query ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - setof jsonb - - - Returns all JSON items returned by the JSON path for the specified - JSON value. - For SQL-standard JSON path expressions it returns the JSON - values selected from target. - For predicate - check expressions it returns the result of the predicate - check: true, false, - or null. - The optional vars - and silent arguments act the same as - for jsonb_path_exists. - - - select * from jsonb_path_query('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}') - - - jsonb_path_query ------------------- - 2 - 3 - 4 - - - - - - - - jsonb_path_query_array - - jsonb_path_query_array ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - jsonb - - - Returns all JSON items returned by the JSON path for the specified - JSON value, as a JSON array. - The parameters are the same as - for jsonb_path_query. - - - jsonb_path_query_array('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}') - [2, 3, 4] - - - - - - - jsonb_path_query_first - - jsonb_path_query_first ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - jsonb - - - Returns the first JSON item returned by the JSON path for the - specified JSON value, or NULL if there are no - results. - The parameters are the same as - for jsonb_path_query. - - - jsonb_path_query_first('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}') - 2 - - - - - - - jsonb_path_exists_tz - - jsonb_path_exists_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - boolean - - - - jsonb_path_match_tz - - jsonb_path_match_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - boolean - - - - jsonb_path_query_tz - - jsonb_path_query_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - setof jsonb - - - - jsonb_path_query_array_tz - - jsonb_path_query_array_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - jsonb - - - - jsonb_path_query_first_tz - - jsonb_path_query_first_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) - jsonb - - - These functions act like their counterparts described above without - the _tz suffix, except that these functions support - comparisons of date/time values that require timezone-aware - conversions. The example below requires interpretation of the - date-only value 2015-08-02 as a timestamp with time - zone, so the result depends on the current - setting. Due to this dependency, these - functions are marked as stable, which means these functions cannot be - used in indexes. Their counterparts are immutable, and so can be used - in indexes; but they will throw errors if asked to make such - comparisons. - - - jsonb_path_exists_tz('["2015-08-01 12:00:00-05"]', '$[*] ? (@.datetime() < "2015-08-02".datetime())') - t - - - - - - - jsonb_pretty - - jsonb_pretty ( jsonb ) - text - - - Converts the given JSON value to pretty-printed, indented text. - - - jsonb_pretty('[{"f1":1,"f2":null}, 2]') - - -[ - { - "f1": 1, - "f2": null - }, - 2 -] - - - - - - - - json_typeof - - json_typeof ( json ) - text - - - - jsonb_typeof - - jsonb_typeof ( jsonb ) - text - - - Returns the type of the top-level JSON value as a text string. - Possible types are - object, array, - string, number, - boolean, and null. - (The null result should not be confused - with an SQL NULL; see the examples.) - - - json_typeof('-123.4') - number - - - json_typeof('null'::json) - null - - - json_typeof(NULL::json) IS NULL - t - - - - -

- - - - The SQL/JSON Path Language - - - SQL/JSON path language - - - - SQL/JSON path expressions specify item(s) to be retrieved - from a JSON value, similarly to XPath expressions used - for access to XML content. In PostgreSQL, - path expressions are implemented as the jsonpath - data type and can use any elements described in - . - - - - JSON query functions and operators - pass the provided path expression to the path engine - for evaluation. If the expression matches the queried JSON data, - the corresponding JSON item, or set of items, is returned. - If there is no match, the result will be NULL, - false, or an error, depending on the function. - Path expressions are written in the SQL/JSON path language - and can include arithmetic expressions and functions. - - - - A path expression consists of a sequence of elements allowed - by the jsonpath data type. - The path expression is normally evaluated from left to right, but - you can use parentheses to change the order of operations. - If the evaluation is successful, a sequence of JSON items is produced, - and the evaluation result is returned to the JSON query function - that completes the specified computation. - - - - To refer to the JSON value being queried (the - context item), use the $ variable - in the path expression. The first element of a path must always - be $. It can be followed by one or more - accessor operators, - which go down the JSON structure level by level to retrieve sub-items - of the context item. Each accessor operator acts on the - result(s) of the previous evaluation step, producing zero, one, or more - output items from each input item. - - - - For example, suppose you have some JSON data from a GPS tracker that you - would like to parse, such as: - -SELECT '{ - "track": { - "segments": [ - { - "location": [ 47.763, 13.4034 ], - "start time": "2018-10-14 10:05:14", - "HR": 73 - }, - { - "location": [ 47.706, 13.2635 ], - "start time": "2018-10-14 10:39:21", - "HR": 135 - } - ] - } -}' AS json \gset - - (The above example can be copied-and-pasted - into psql to set things up for the following - examples. Then psql will - expand :'json' into a suitably-quoted string - constant containing the JSON value.) - - - - To retrieve the available track segments, you need to use the - .key accessor - operator to descend through surrounding JSON objects, for example: - -=> select jsonb_path_query(:'json', '$.track.segments'); - jsonb_path_query ------------------------------------------------------------&zwsp;-----------------------------------------------------------&zwsp;--------------------------------------------- - [{"HR": 73, "location": [47.763, 13.4034], "start time": "2018-10-14 10:05:14"}, {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"}] - - - - - To retrieve the contents of an array, you typically use the - [*] operator. - The following example will return the location coordinates for all - the available track segments: - -=> select jsonb_path_query(:'json', '$.track.segments[*].location'); - jsonb_path_query -------------------- - [47.763, 13.4034] - [47.706, 13.2635] - - Here we started with the whole JSON input value ($), - then the .track accessor selected the JSON object - associated with the "track" object key, then - the .segments accessor selected the JSON array - associated with the "segments" key within that - object, then the [*] accessor selected each element - of that array (producing a series of items), then - the .location accessor selected the JSON array - associated with the "location" key within each of - those objects. In this example, each of those objects had - a "location" key; but if any of them did not, - the .location accessor would have simply produced no - output for that input item. - - - - To return the coordinates of the first segment only, you can - specify the corresponding subscript in the [] - accessor operator. Recall that JSON array indexes are 0-relative: - -=> select jsonb_path_query(:'json', '$.track.segments[0].location'); - jsonb_path_query -------------------- - [47.763, 13.4034] - - - - - The result of each path evaluation step can be processed - by one or more of the jsonpath operators and methods - listed in . - Each method name must be preceded by a dot. For example, - you can get the size of an array: - -=> select jsonb_path_query(:'json', '$.track.segments.size()'); - jsonb_path_query ------------------- - 2 - - More examples of using jsonpath operators - and methods within path expressions appear below in - . - - - - A path can also contain - filter expressions that work similarly to the - WHERE clause in SQL. A filter expression begins with - a question mark and provides a condition in parentheses: - - -? (condition) - - - - - Filter expressions must be written just after the path evaluation step - to which they should apply. The result of that step is filtered to include - only those items that satisfy the provided condition. SQL/JSON defines - three-valued logic, so the condition can - produce true, false, - or unknown. The unknown value - plays the same role as SQL NULL and can be tested - for with the is unknown predicate. Further path - evaluation steps use only those items for which the filter expression - returned true. - - - - The functions and operators that can be used in filter expressions are - listed in . Within a - filter expression, the @ variable denotes the value - being considered (i.e., one result of the preceding path step). You can - write accessor operators after @ to retrieve component - items. - - - - For example, suppose you would like to retrieve all heart rate values higher - than 130. You can achieve this as follows: - -=> select jsonb_path_query(:'json', '$.track.segments[*].HR ? (@ > 130)'); - jsonb_path_query ------------------- - 135 - - - - - To get the start times of segments with such values, you have to - filter out irrelevant segments before selecting the start times, so the - filter expression is applied to the previous step, and the path used - in the condition is different: - -=> select jsonb_path_query(:'json', '$.track.segments[*] ? (@.HR > 130)."start time"'); - jsonb_path_query ------------------------ - "2018-10-14 10:39:21" - - - - - You can use several filter expressions in sequence, if required. - The following example selects start times of all segments that - contain locations with relevant coordinates and high heart rate values: - -=> select jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] < 13.4) ? (@.HR > 130)."start time"'); - jsonb_path_query ------------------------ - "2018-10-14 10:39:21" - - - - - Using filter expressions at different nesting levels is also allowed. - The following example first filters all segments by location, and then - returns high heart rate values for these segments, if available: - -=> select jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] < 13.4).HR ? (@ > 130)'); - jsonb_path_query ------------------- - 135 - - - - - You can also nest filter expressions within each other. - This example returns the size of the track if it contains any - segments with high heart rate values, or an empty sequence otherwise: - -=> select jsonb_path_query(:'json', '$.track ? (exists(@.segments[*] ? (@.HR > 130))).segments.size()'); - jsonb_path_query ------------------- - 2 - - - - - Deviations from the SQL Standard - - PostgreSQL's implementation of the SQL/JSON path - language has the following deviations from the SQL/JSON standard. - - - - Boolean Predicate Check Expressions - - As an extension to the SQL standard, - a PostgreSQL path expression can be a - Boolean predicate, whereas the SQL standard allows predicates only within - filters. While SQL-standard path expressions return the relevant - element(s) of the queried JSON value, predicate check expressions - return the single three-valued jsonb result of the - predicate: true, - false, or null. - For example, we could write this SQL-standard filter expression: - -=> select jsonb_path_query(:'json', '$.track.segments ?(@[*].HR > 130)'); - jsonb_path_query ------------------------------------------------------------&zwsp;---------------------- - {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"} - - The similar predicate check expression simply - returns true, indicating that a match exists: - -=> select jsonb_path_query(:'json', '$.track.segments[*].HR > 130'); - jsonb_path_query ------------------- - true - - - - - - Predicate check expressions are required in the - @@ operator (and the - jsonb_path_match function), and should not be used - with the @? operator (or the - jsonb_path_exists function). - - - - - - Regular Expression Interpretation - - There are minor differences in the interpretation of regular - expression patterns used in like_regex filters, as - described in . - - - - - - Strict and Lax Modes - - When you query JSON data, the path expression may not match the - actual JSON data structure. An attempt to access a non-existent - member of an object or element of an array is defined as a - structural error. SQL/JSON path expressions have two modes - of handling structural errors: - - - - - - lax (default) — the path engine implicitly adapts - the queried data to the specified path. - Any structural errors that cannot be fixed as described below - are suppressed, producing no match. - - - - - strict — if a structural error occurs, an error is raised. - - - - - - Lax mode facilitates matching of a JSON document and path - expression when the JSON data does not conform to the expected schema. - If an operand does not match the requirements of a particular operation, - it can be automatically wrapped as an SQL/JSON array, or unwrapped by - converting its elements into an SQL/JSON sequence before performing - the operation. Also, comparison operators automatically unwrap their - operands in lax mode, so you can compare SQL/JSON arrays - out-of-the-box. An array of size 1 is considered equal to its sole element. - Automatic unwrapping is not performed when: - - - - The path expression contains type() or - size() methods that return the type - and the number of elements in the array, respectively. - - - - - The queried JSON data contain nested arrays. In this case, only - the outermost array is unwrapped, while all the inner arrays - remain unchanged. Thus, implicit unwrapping can only go one - level down within each path evaluation step. - - - - - - - For example, when querying the GPS data listed above, you can - abstract from the fact that it stores an array of segments - when using lax mode: - -=> select jsonb_path_query(:'json', 'lax $.track.segments.location'); - jsonb_path_query -------------------- - [47.763, 13.4034] - [47.706, 13.2635] - - - - - In strict mode, the specified path must exactly match the structure of - the queried JSON document, so using this path - expression will cause an error: - -=> select jsonb_path_query(:'json', 'strict $.track.segments.location'); -ERROR: jsonpath member accessor can only be applied to an object - - To get the same result as in lax mode, you have to explicitly unwrap the - segments array: - -=> select jsonb_path_query(:'json', 'strict $.track.segments[*].location'); - jsonb_path_query -------------------- - [47.763, 13.4034] - [47.706, 13.2635] - - - - - The unwrapping behavior of lax mode can lead to surprising results. For - instance, the following query using the .** accessor - selects every HR value twice: - -=> select jsonb_path_query(:'json', 'lax $.**.HR'); - jsonb_path_query ------------------- - 73 - 135 - 73 - 135 - - This happens because the .** accessor selects both - the segments array and each of its elements, while - the .HR accessor automatically unwraps arrays when - using lax mode. To avoid surprising results, we recommend using - the .** accessor only in strict mode. The - following query selects each HR value just once: - -=> select jsonb_path_query(:'json', 'strict $.**.HR'); - jsonb_path_query ------------------- - 73 - 135 - - - - - The unwrapping of arrays can also lead to unexpected results. Consider this - example, which selects all the location arrays: - -=> select jsonb_path_query(:'json', 'lax $.track.segments[*].location'); - jsonb_path_query -------------------- - [47.763, 13.4034] - [47.706, 13.2635] -(2 rows) - - As expected it returns the full arrays. But applying a filter expression - causes the arrays to be unwrapped to evaluate each item, returning only the - items that match the expression: - -=> select jsonb_path_query(:'json', 'lax $.track.segments[*].location ?(@[*] > 15)'); - jsonb_path_query ------------------- - 47.763 - 47.706 -(2 rows) - - This despite the fact that the full arrays are selected by the path - expression. Use strict mode to restore selecting the arrays: - -=> select jsonb_path_query(:'json', 'strict $.track.segments[*].location ?(@[*] > 15)'); - jsonb_path_query -------------------- - [47.763, 13.4034] - [47.706, 13.2635] -(2 rows) - - - - - - SQL/JSON Path Operators and Methods - - - shows the operators and - methods available in jsonpath. Note that while the unary - operators and methods can be applied to multiple values resulting from a - preceding path step, the binary operators (addition etc.) can only be - applied to single values. In lax mode, methods applied to an array will be - executed for each value in the array. The exceptions are - .type() and .size(), which apply to - the array itself. - - - - <type>jsonpath</type> Operators and Methods - - - - - Operator/Method - - - Description - - - Example(s) - - - - - - - - number + number - number - - - Addition - - - jsonb_path_query('[2]', '$[0] + 3') - 5 - - - - - - + number - number - - - Unary plus (no operation); unlike addition, this can iterate over - multiple values - - - jsonb_path_query_array('{"x": [2,3,4]}', '+ $.x') - [2, 3, 4] - - - - - - number - number - number - - - Subtraction - - - jsonb_path_query('[2]', '7 - $[0]') - 5 - - - - - - - number - number - - - Negation; unlike subtraction, this can iterate over - multiple values - - - jsonb_path_query_array('{"x": [2,3,4]}', '- $.x') - [-2, -3, -4] - - - - - - number * number - number - - - Multiplication - - - jsonb_path_query('[4]', '2 * $[0]') - 8 - - - - - - number / number - number - - - Division - - - jsonb_path_query('[8.5]', '$[0] / 2') - 4.2500000000000000 - - - - - - number % number - number - - - Modulo (remainder) - - - jsonb_path_query('[32]', '$[0] % 10') - 2 - - - - - - value . type() - string - - - Type of the JSON item (see json_typeof) - - - jsonb_path_query_array('[1, "2", {}]', '$[*].type()') - ["number", "string", "object"] - - - - - - value . size() - number - - - Size of the JSON item (number of array elements, or 1 if not an - array) - - - jsonb_path_query('{"m": [11, 15]}', '$.m.size()') - 2 - - - - - - value . boolean() - boolean - - - Boolean value converted from a JSON boolean, number, or string - - - jsonb_path_query_array('[1, "yes", false]', '$[*].boolean()') - [true, true, false] - - - - - - value . string() - string - - - String value converted from a JSON boolean, number, string, or - datetime - - - jsonb_path_query_array('[1.23, "xyz", false]', '$[*].string()') - ["1.23", "xyz", "false"] - - - jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp().string()') - "2023-08-15T12:34:56" - - - - - - value . double() - number - - - Approximate floating-point number converted from a JSON number or - string - - - jsonb_path_query('{"len": "1.9"}', '$.len.double() * 2') - 3.8 - - - - - - number . ceiling() - number - - - Nearest integer greater than or equal to the given number - - - jsonb_path_query('{"h": 1.3}', '$.h.ceiling()') - 2 - - - - - - number . floor() - number - - - Nearest integer less than or equal to the given number - - - jsonb_path_query('{"h": 1.7}', '$.h.floor()') - 1 - - - - - - number . abs() - number - - - Absolute value of the given number - - - jsonb_path_query('{"z": -0.3}', '$.z.abs()') - 0.3 - - - - - - value . bigint() - bigint - - - Big integer value converted from a JSON number or string - - - jsonb_path_query('{"len": "9876543219"}', '$.len.bigint()') - 9876543219 - - - - - - value . decimal( [ precision [ , scale ] ] ) - decimal - - - Rounded decimal value converted from a JSON number or string - (precision and scale must be - integer values) - - - jsonb_path_query('1234.5678', '$.decimal(6, 2)') - 1234.57 - - - - - - value . integer() - integer - - - Integer value converted from a JSON number or string - - - jsonb_path_query('{"len": "12345"}', '$.len.integer()') - 12345 - - - - - - value . number() - numeric - - - Numeric value converted from a JSON number or string - - - jsonb_path_query('{"len": "123.45"}', '$.len.number()') - 123.45 - - - - - - string . datetime() - datetime_type - (see note) - - - Date/time value converted from a string - - - jsonb_path_query('["2015-8-1", "2015-08-12"]', '$[*] ? (@.datetime() < "2015-08-2".datetime())') - "2015-8-1" - - - - - - string . datetime(template) - datetime_type - (see note) - - - Date/time value converted from a string using the - specified to_timestamp template - - - jsonb_path_query_array('["12:30", "18:40"]', '$[*].datetime("HH24:MI")') - ["12:30:00", "18:40:00"] - - - - - - string . date() - date - - - Date value converted from a string - - - jsonb_path_query('"2023-08-15"', '$.date()') - "2023-08-15" - - - - - - string . time() - time without time zone - - - Time without time zone value converted from a string - - - jsonb_path_query('"12:34:56"', '$.time()') - "12:34:56" - - - - - - string . time(precision) - time without time zone - - - Time without time zone value converted from a string, with fractional - seconds adjusted to the given precision - - - jsonb_path_query('"12:34:56.789"', '$.time(2)') - "12:34:56.79" - - - - - - string . time_tz() - time with time zone - - - Time with time zone value converted from a string - - - jsonb_path_query('"12:34:56 +05:30"', '$.time_tz()') - "12:34:56+05:30" - - - - - - string . time_tz(precision) - time with time zone - - - Time with time zone value converted from a string, with fractional - seconds adjusted to the given precision - - - jsonb_path_query('"12:34:56.789 +05:30"', '$.time_tz(2)') - "12:34:56.79+05:30" - - - - - - string . timestamp() - timestamp without time zone - - - Timestamp without time zone value converted from a string - - - jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp()') - "2023-08-15T12:34:56" - - - - - - string . timestamp(precision) - timestamp without time zone - - - Timestamp without time zone value converted from a string, with - fractional seconds adjusted to the given precision - - - jsonb_path_query('"2023-08-15 12:34:56.789"', '$.timestamp(2)') - "2023-08-15T12:34:56.79" - - - - - - string . timestamp_tz() - timestamp with time zone - - - Timestamp with time zone value converted from a string - - - jsonb_path_query('"2023-08-15 12:34:56 +05:30"', '$.timestamp_tz()') - "2023-08-15T12:34:56+05:30" - - - - - - string . timestamp_tz(precision) - timestamp with time zone - - - Timestamp with time zone value converted from a string, with fractional - seconds adjusted to the given precision - - - jsonb_path_query('"2023-08-15 12:34:56.789 +05:30"', '$.timestamp_tz(2)') - "2023-08-15T12:34:56.79+05:30" - - - - - - object . keyvalue() - array - - - The object's key-value pairs, represented as an array of objects - containing three fields: "key", - "value", and "id"; - "id" is a unique identifier of the object the - key-value pair belongs to - - - jsonb_path_query_array('{"x": "20", "y": 32}', '$.keyvalue()') - [{"id": 0, "key": "x", "value": "20"}, {"id": 0, "key": "y", "value": 32}] - - - - -

- - - - The result type of the datetime() and - datetime(template) - methods can be date, timetz, time, - timestamptz, or timestamp. - Both methods determine their result type dynamically. - - - The datetime() method sequentially tries to - match its input string to the ISO formats - for date, timetz, time, - timestamptz, and timestamp. It stops on - the first matching format and emits the corresponding data type. - - - The datetime(template) - method determines the result type according to the fields used in the - provided template string. - - - The datetime() and - datetime(template) methods - use the same parsing rules as the to_timestamp SQL - function does (see ), with three - exceptions. First, these methods don't allow unmatched template - patterns. Second, only the following separators are allowed in the - template string: minus sign, period, solidus (slash), comma, apostrophe, - semicolon, colon and space. Third, separators in the template string - must exactly match the input string. - - - If different date/time types need to be compared, an implicit cast is - applied. A date value can be cast to timestamp - or timestamptz, timestamp can be cast to - timestamptz, and time to timetz. - However, all but the first of these conversions depend on the current - setting, and thus can only be performed - within timezone-aware jsonpath functions. Similarly, other - date/time-related methods that convert strings to date/time types - also do this casting, which may involve the current - setting. Therefore, these conversions can - also only be performed within timezone-aware jsonpath - functions. - - - - - shows the available - filter expression elements. - - - - <type>jsonpath</type> Filter Expression Elements - - - - - Predicate/Value - - - Description - - - Example(s) - - - - - - - - value == value - boolean - - - Equality comparison (this, and the other comparison operators, work on - all JSON scalar values) - - - jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == 1)') - [1, 1] - - - jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == "a")') - ["a"] - - - - - - value != value - boolean - - - value <> value - boolean - - - Non-equality comparison - - - jsonb_path_query_array('[1, 2, 1, 3]', '$[*] ? (@ != 1)') - [2, 3] - - - jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ <> "b")') - ["a", "c"] - - - - - - value < value - boolean - - - Less-than comparison - - - jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ < 2)') - [1] - - - - - - value <= value - boolean - - - Less-than-or-equal-to comparison - - - jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ <= "b")') - ["a", "b"] - - - - - - value > value - boolean - - - Greater-than comparison - - - jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ > 2)') - [3] - - - - - - value >= value - boolean - - - Greater-than-or-equal-to comparison - - - jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ >= 2)') - [2, 3] - - - - - - true - boolean - - - JSON constant true - - - jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == true)') - {"name": "Chris", "parent": true} - - - - - - false - boolean - - - JSON constant false - - - jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == false)') - {"name": "John", "parent": false} - - - - - - null - value - - - JSON constant null (note that, unlike in SQL, - comparison to null works normally) - - - jsonb_path_query('[{"name": "Mary", "job": null}, {"name": "Michael", "job": "driver"}]', '$[*] ? (@.job == null) .name') - "Mary" - - - - - - boolean && boolean - boolean - - - Boolean AND - - - jsonb_path_query('[1, 3, 7]', '$[*] ? (@ > 1 && @ < 5)') - 3 - - - - - - boolean || boolean - boolean - - - Boolean OR - - - jsonb_path_query('[1, 3, 7]', '$[*] ? (@ < 1 || @ > 5)') - 7 - - - - - - ! boolean - boolean - - - Boolean NOT - - - jsonb_path_query('[1, 3, 7]', '$[*] ? (!(@ < 5))') - 7 - - - - - - boolean is unknown - boolean - - - Tests whether a Boolean condition is unknown. - - - jsonb_path_query('[-1, 2, 7, "foo"]', '$[*] ? ((@ > 0) is unknown)') - "foo" - - - - - - string like_regex string flag string - boolean - - - Tests whether the first operand matches the regular expression - given by the second operand, optionally with modifications - described by a string of flag characters (see - ). - - - jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c")') - ["abc", "abdacb"] - - - jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c" flag "i")') - ["abc", "aBdC", "abdacb"] - - - - - - string starts with string - boolean - - - Tests whether the second operand is an initial substring of the first - operand. - - - jsonb_path_query('["John Smith", "Mary Stone", "Bob Johnson"]', '$[*] ? (@ starts with "John")') - "John Smith" - - - - - - exists ( path_expression ) - boolean - - - Tests whether a path expression matches at least one SQL/JSON item. - Returns unknown if the path expression would result - in an error; the second example uses this to avoid a no-such-key error - in strict mode. - - - jsonb_path_query('{"x": [1, 2], "y": [2, 4]}', 'strict $.* ? (exists (@ ? (@[*] > 2)))') - [2, 4] - - - jsonb_path_query_array('{"value": 41}', 'strict $ ? (exists (@.name)) .name') - [] - - - - -

- - - - - SQL/JSON Regular Expressions - - - LIKE_REGEX - in SQL/JSON - - - - SQL/JSON path expressions allow matching text to a regular expression - with the like_regex filter. For example, the - following SQL/JSON path query would case-insensitively match all - strings in an array that start with an English vowel: - -$[*] ? (@ like_regex "^[aeiou]" flag "i") - - - - - The optional flag string may include one or more of - the characters - i for case-insensitive match, - m to allow ^ - and $ to match at newlines, - s to allow . to match a newline, - and q to quote the whole pattern (reducing the - behavior to a simple substring match). - - - - The SQL/JSON standard borrows its definition for regular expressions - from the LIKE_REGEX operator, which in turn uses the - XQuery standard. PostgreSQL does not currently support the - LIKE_REGEX operator. Therefore, - the like_regex filter is implemented using the - POSIX regular expression engine described in - . This leads to various minor - discrepancies from standard SQL/JSON behavior, which are cataloged in - . - Note, however, that the flag-letter incompatibilities described there - do not apply to SQL/JSON, as it translates the XQuery flag letters to - match what the POSIX engine expects. - - - - Keep in mind that the pattern argument of like_regex - is a JSON path string literal, written according to the rules given in - . This means in particular that any - backslashes you want to use in the regular expression must be doubled. - For example, to match string values of the root document that contain - only digits: - -$.* ? (@ like_regex "^\\d+$") - - - - - - - SQL/JSON Query Functions - - SQL/JSON functions JSON_EXISTS(), - JSON_QUERY(), and JSON_VALUE() - described in can be used - to query JSON documents. Each of these functions apply a - path_expression (an SQL/JSON path query) to a - context_item (the document). See - for more details on what - the path_expression can contain. The - path_expression can also reference variables, - whose values are specified with their respective names in the - PASSING clause that is supported by each function. - context_item can be a jsonb value - or a character string that can be successfully cast to jsonb. - - - - SQL/JSON Query Functions - - - - - Function signature - - - Description - - - Example(s) - - - - - - - json_exists - -JSON_EXISTS ( -context_item, path_expression - PASSING { value AS varname } , ... -{ TRUE | FALSE | UNKNOWN | ERROR } ON ERROR ) boolean - - - - - - Returns true if the SQL/JSON path_expression - applied to the context_item yields any - items, false otherwise. - - - - - The ON ERROR clause specifies the behavior if - an error occurs during path_expression - evaluation. Specifying ERROR will cause an error to - be thrown with the appropriate message. Other options include - returning boolean values FALSE or - TRUE or the value UNKNOWN which - is actually an SQL NULL. The default when no ON ERROR - clause is specified is to return the boolean value - FALSE. - - - - - Examples: - - - JSON_EXISTS(jsonb '{"key1": [1,2,3]}', 'strict $.key1[*] ? (@ > $x)' PASSING 2 AS x) - t - - - JSON_EXISTS(jsonb '{"a": [1,2,3]}', 'lax $.a[5]' ERROR ON ERROR) - f - - - JSON_EXISTS(jsonb '{"a": [1,2,3]}', 'strict $.a[5]' ERROR ON ERROR) - - -ERROR: jsonpath array subscript is out of bounds - - - - - - json_query - -JSON_QUERY ( -context_item, path_expression - PASSING { value AS varname } , ... - RETURNING data_type FORMAT JSON ENCODING UTF8 - { WITHOUT | WITH { CONDITIONAL | UNCONDITIONAL } } ARRAY WRAPPER - { KEEP | OMIT } QUOTES ON SCALAR STRING - { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON EMPTY - { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON ERROR ) jsonb - - - - - - Returns the result of applying the SQL/JSON - path_expression to the - context_item. - - - - - By default, the result is returned as a value of type jsonb, - though the RETURNING clause can be used to return - as some other type to which it can be successfully coerced. - - - - - If the path expression may return multiple values, it might be necessary - to wrap those values using the WITH WRAPPER clause to - make it a valid JSON string, because the default behavior is to not wrap - them, as if WITHOUT WRAPPER were specified. The - WITH WRAPPER clause is by default taken to mean - WITH UNCONDITIONAL WRAPPER, which means that even a - single result value will be wrapped. To apply the wrapper only when - multiple values are present, specify WITH CONDITIONAL WRAPPER. - Getting multiple values in result will be treated as an error if - WITHOUT WRAPPER is specified. - - - - - If the result is a scalar string, by default, the returned value will - be surrounded by quotes, making it a valid JSON value. It can be made - explicit by specifying KEEP QUOTES. Conversely, - quotes can be omitted by specifying OMIT QUOTES. - To ensure that the result is a valid JSON value, OMIT QUOTES - cannot be specified when WITH WRAPPER is also - specified. - - - - - The ON EMPTY clause specifies the behavior if - evaluating path_expression yields an empty - set. The ON ERROR clause specifies the behavior - if an error occurs when evaluating path_expression, - when coercing the result value to the RETURNING type, - or when evaluating the ON EMPTY expression if the - path_expression evaluation returns an empty - set. - - - - - For both ON EMPTY and ON ERROR, - specifying ERROR will cause an error to be thrown with - the appropriate message. Other options include returning an SQL NULL, an - empty array (EMPTY ARRAY), - an empty object (EMPTY OBJECT), or a user-specified - expression (DEFAULT expression) - that can be coerced to jsonb or the type specified in RETURNING. - The default when ON EMPTY or ON ERROR - is not specified is to return an SQL NULL value. - - - - - Examples: - - - JSON_QUERY(jsonb '[1,[2,3],null]', 'lax $[*][$off]' PASSING 1 AS off WITH CONDITIONAL WRAPPER) - 3 - - - JSON_QUERY(jsonb '{"a": "[1, 2]"}', 'lax $.a' OMIT QUOTES) - [1, 2] - - - JSON_QUERY(jsonb '{"a": "[1, 2]"}', 'lax $.a' RETURNING int[] OMIT QUOTES ERROR ON ERROR) - - -ERROR: malformed array literal: "[1, 2]" -DETAIL: Missing "]" after array dimensions. - - - - - - - json_value - -JSON_VALUE ( -context_item, path_expression - PASSING { value AS varname } , ... - RETURNING data_type - { ERROR | NULL | DEFAULT expression } ON EMPTY - { ERROR | NULL | DEFAULT expression } ON ERROR ) text - - - - - - Returns the result of applying the SQL/JSON - path_expression to the - context_item. - - - - - Only use JSON_VALUE() if the extracted value is - expected to be a single SQL/JSON scalar item; - getting multiple values will be treated as an error. If you expect that - extracted value might be an object or an array, use the - JSON_QUERY function instead. - - - - - By default, the result, which must be a single scalar value, is - returned as a value of type text, though the - RETURNING clause can be used to return as some - other type to which it can be successfully coerced. - - - - - The ON ERROR and ON EMPTY - clauses have similar semantics as mentioned in the description of - JSON_QUERY, except the set of values returned in - lieu of throwing an error is different. - - - - - Note that scalar strings returned by JSON_VALUE - always have their quotes removed, equivalent to specifying - OMIT QUOTES in JSON_QUERY. - - - - - Examples: - - - JSON_VALUE(jsonb '"123.45"', '$' RETURNING float) - 123.45 - - - JSON_VALUE(jsonb '"03:04 2015-02-01"', '$.datetime("HH24:MI YYYY-MM-DD")' RETURNING date) - 2015-02-01 - - - JSON_VALUE(jsonb '[1,2]', 'strict $[$off]' PASSING 1 as off) - 2 - - - JSON_VALUE(jsonb '[1,2]', 'strict $[*]' DEFAULT 9 ON ERROR) - 9 - - - - - -

- - - The context_item expression is converted to - jsonb by an implicit cast if the expression is not already of - type jsonb. Note, however, that any parsing errors that occur - during that conversion are thrown unconditionally, that is, are not - handled according to the (specified or implicit) ON ERROR - clause. - - - - - JSON_VALUE() returns an SQL NULL if - path_expression returns a JSON - null, whereas JSON_QUERY() returns - the JSON null as is. - - - - - - JSON_TABLE - - json_table - - - - JSON_TABLE is an SQL/JSON function which - queries JSON data - and presents the results as a relational view, which can be accessed as a - regular SQL table. You can use JSON_TABLE inside - the FROM clause of a SELECT, - UPDATE, or DELETE and as data source - in a MERGE statement. - - - - Taking JSON data as input, JSON_TABLE uses a JSON path - expression to extract a part of the provided data to use as a - row pattern for the constructed view. Each SQL/JSON - value given by the row pattern serves as source for a separate row in the - constructed view. - - - - To split the row pattern into columns, JSON_TABLE - provides the COLUMNS clause that defines the - schema of the created view. For each column, a separate JSON path expression - can be specified to be evaluated against the row pattern to get an SQL/JSON - value that will become the value for the specified column in a given output - row. - - - - JSON data stored at a nested level of the row pattern can be extracted using - the NESTED PATH clause. Each - NESTED PATH clause can be used to generate one or more - columns using the data from a nested level of the row pattern. Those - columns can be specified using a COLUMNS clause that - looks similar to the top-level COLUMNS clause. Rows constructed from - NESTED COLUMNS are called child rows and are joined - against the row constructed from the columns specified in the parent - COLUMNS clause to get the row in the final view. Child - columns themselves may contain a NESTED PATH - specification thus allowing to extract data located at arbitrary nesting - levels. Columns produced by multiple NESTED PATHs at the - same level are considered to be siblings of each - other and their rows after joining with the parent row are combined using - UNION. - - - - The rows produced by JSON_TABLE are laterally - joined to the row that generated them, so you do not have to explicitly join - the constructed view with the original table holding JSON - data. - - - - The syntax is: - - - -JSON_TABLE ( - context_item, path_expression AS json_path_name PASSING { value AS varname } , ... - COLUMNS ( json_table_column , ... ) - { ERROR | EMPTY ARRAY} ON ERROR -) - - -where json_table_column is: - - name FOR ORDINALITY - | name type - FORMAT JSON ENCODING UTF8 - PATH path_expression - { WITHOUT | WITH { CONDITIONAL | UNCONDITIONAL } } ARRAY WRAPPER - { KEEP | OMIT } QUOTES ON SCALAR STRING - { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON EMPTY - { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON ERROR - | name type EXISTS PATH path_expression - { ERROR | TRUE | FALSE | UNKNOWN } ON ERROR - | NESTED PATH path_expression AS json_path_name COLUMNS ( json_table_column , ... ) - - - - Each syntax element is described below in more detail. - - - - - - context_item, path_expression AS json_path_name PASSING { value AS varname } , ... - - - - The context_item specifies the input document - to query, the path_expression is an SQL/JSON - path expression defining the query, and json_path_name - is an optional name for the path_expression. - The optional PASSING clause provides data values for - the variables mentioned in the path_expression. - The result of the input data evaluation using the aforementioned elements - is called the row pattern, which is used as the - source for row values in the constructed view. - - - - - - - COLUMNS ( json_table_column , ... ) - - - - - The COLUMNS clause defining the schema of the - constructed view. In this clause, you can specify each column to be - filled with an SQL/JSON value obtained by applying a JSON path expression - against the row pattern. json_table_column has - the following variants: - - - - - - name FOR ORDINALITY - - - - Adds an ordinality column that provides sequential row numbering starting - from 1. Each NESTED PATH (see below) gets its own - counter for any nested ordinality columns. - - - - - - - name type - FORMAT JSON ENCODING UTF8 - PATH path_expression - - - - Inserts an SQL/JSON value obtained by applying - path_expression against the row pattern into - the view's output row after coercing it to specified - type. - - - Specifying FORMAT JSON makes it explicit that you - expect the value to be a valid json object. It only - makes sense to specify FORMAT JSON if - type is one of bpchar, - bytea, character varying, name, - json, jsonb, text, or a domain over - these types. - - - Optionally, you can specify WRAPPER and - QUOTES clauses to format the output. Note that - specifying OMIT QUOTES overrides - FORMAT JSON if also specified, because unquoted - literals do not constitute valid json values. - - - Optionally, you can use ON EMPTY and - ON ERROR clauses to specify whether to throw the error - or return the specified value when the result of JSON path evaluation is - empty and when an error occurs during JSON path evaluation or when - coercing the SQL/JSON value to the specified type, respectively. The - default for both is to return a NULL value. - - - - This clause is internally turned into and has the same semantics as - JSON_VALUE or JSON_QUERY. - The latter if the specified type is not a scalar type or if either of - FORMAT JSON, WRAPPER, or - QUOTES clause is present. - - - - - - - - name type - EXISTS PATH path_expression - - - - Inserts a boolean value obtained by applying - path_expression against the row pattern - into the view's output row after coercing it to specified - type. - - - The value corresponds to whether applying the PATH - expression to the row pattern yields any values. - - - The specified type should have a cast from the - boolean type. - - - Optionally, you can use ON ERROR to specify whether to - throw the error or return the specified value when an error occurs during - JSON path evaluation or when coercing SQL/JSON value to the specified - type. The default is to return a boolean value - FALSE. - - - - This clause is internally turned into and has the same semantics as - JSON_EXISTS. - - - - - - - - NESTED PATH path_expression AS json_path_name - COLUMNS ( json_table_column , ... ) - - - - - Extracts SQL/JSON values from nested levels of the row pattern, - generates one or more columns as defined by the COLUMNS - subclause, and inserts the extracted SQL/JSON values into those - columns. The json_table_column - expression in the COLUMNS subclause uses the same - syntax as in the parent COLUMNS clause. - - - - The NESTED PATH syntax is recursive, - so you can go down multiple nested levels by specifying several - NESTED PATH subclauses within each other. - It allows to unnest the hierarchy of JSON objects and arrays - in a single function invocation rather than chaining several - JSON_TABLE expressions in an SQL statement. - - - - - - - - In each variant of json_table_column described - above, if the PATH clause is omitted, path expression - $.name is used, where - name is the provided column name. - - - - - - - - - AS json_path_name - - - - - The optional json_path_name serves as an - identifier of the provided path_expression. - The name must be unique and distinct from the column names. - - - - - - - { ERROR | EMPTY } ON ERROR - - - - - The optional ON ERROR can be used to specify how to - handle errors when evaluating the top-level - path_expression. Use ERROR - if you want the errors to be thrown and EMPTY to - return an empty table, that is, a table containing 0 rows. Note that - this clause does not affect the errors that occur when evaluating - columns, for which the behavior depends on whether the - ON ERROR clause is specified against a given column. - - - - - - Examples - - - In the examples that follow, the following table containing JSON data - will be used: - - -CREATE TABLE my_films ( js jsonb ); - -INSERT INTO my_films VALUES ( -'{ "favorites" : [ - { "kind" : "comedy", "films" : [ - { "title" : "Bananas", - "director" : "Woody Allen"}, - { "title" : "The Dinner Game", - "director" : "Francis Veber" } ] }, - { "kind" : "horror", "films" : [ - { "title" : "Psycho", - "director" : "Alfred Hitchcock" } ] }, - { "kind" : "thriller", "films" : [ - { "title" : "Vertigo", - "director" : "Alfred Hitchcock" } ] }, - { "kind" : "drama", "films" : [ - { "title" : "Yojimbo", - "director" : "Akira Kurosawa" } ] } - ] }'); - - - - - The following query shows how to use JSON_TABLE to - turn the JSON objects in the my_films table - to a view containing columns for the keys kind, - title, and director contained in - the original JSON along with an ordinality column: - - -SELECT jt.* FROM - my_films, - JSON_TABLE (js, '$.favorites[*]' COLUMNS ( - id FOR ORDINALITY, - kind text PATH '$.kind', - title text PATH '$.films[*].title' WITH WRAPPER, - director text PATH '$.films[*].director' WITH WRAPPER)) AS jt; - - - - id | kind | title | director -----+----------+--------------------------------+---------------------------------- - 1 | comedy | ["Bananas", "The Dinner Game"] | ["Woody Allen", "Francis Veber"] - 2 | horror | ["Psycho"] | ["Alfred Hitchcock"] - 3 | thriller | ["Vertigo"] | ["Alfred Hitchcock"] - 4 | drama | ["Yojimbo"] | ["Akira Kurosawa"] -(4 rows) - - - - - The following is a modified version of the above query to show the - usage of PASSING arguments in the filter specified in - the top-level JSON path expression and the various options for the - individual columns: - - -SELECT jt.* FROM - my_films, - JSON_TABLE (js, '$.favorites[*] ? (@.films[*].director == $filter)' - PASSING 'Alfred Hitchcock' AS filter - COLUMNS ( - id FOR ORDINALITY, - kind text PATH '$.kind', - title text FORMAT JSON PATH '$.films[*].title' OMIT QUOTES, - director text PATH '$.films[*].director' KEEP QUOTES)) AS jt; - - - - id | kind | title | director -----+----------+---------+-------------------- - 1 | horror | Psycho | "Alfred Hitchcock" - 2 | thriller | Vertigo | "Alfred Hitchcock" -(2 rows) - - - - - The following is a modified version of the above query to show the usage - of NESTED PATH for populating title and director - columns, illustrating how they are joined to the parent columns id and - kind: - - -SELECT jt.* FROM - my_films, - JSON_TABLE ( js, '$.favorites[*] ? (@.films[*].director == $filter)' - PASSING 'Alfred Hitchcock' AS filter - COLUMNS ( - id FOR ORDINALITY, - kind text PATH '$.kind', - NESTED PATH '$.films[*]' COLUMNS ( - title text FORMAT JSON PATH '$.title' OMIT QUOTES, - director text PATH '$.director' KEEP QUOTES))) AS jt; - - - - id | kind | title | director -----+----------+---------+-------------------- - 1 | horror | Psycho | "Alfred Hitchcock" - 2 | thriller | Vertigo | "Alfred Hitchcock" -(2 rows) - - - - - - The following is the same query but without the filter in the root - path: - - -SELECT jt.* FROM - my_films, - JSON_TABLE ( js, '$.favorites[*]' - COLUMNS ( - id FOR ORDINALITY, - kind text PATH '$.kind', - NESTED PATH '$.films[*]' COLUMNS ( - title text FORMAT JSON PATH '$.title' OMIT QUOTES, - director text PATH '$.director' KEEP QUOTES))) AS jt; - - - - id | kind | title | director -----+----------+-----------------+-------------------- - 1 | comedy | Bananas | "Woody Allen" - 1 | comedy | The Dinner Game | "Francis Veber" - 2 | horror | Psycho | "Alfred Hitchcock" - 3 | thriller | Vertigo | "Alfred Hitchcock" - 4 | drama | Yojimbo | "Akira Kurosawa" -(5 rows) - - - - - - The following shows another query using a different JSON - object as input. It shows the UNION "sibling join" between - NESTED paths $.movies[*] and - $.books[*] and also the usage of - FOR ORDINALITY column at NESTED - levels (columns movie_id, book_id, - and author_id): - - -SELECT * FROM JSON_TABLE ( -'{"favorites": - [{"movies": - [{"name": "One", "director": "John Doe"}, - {"name": "Two", "director": "Don Joe"}], - "books": - [{"name": "Mystery", "authors": [{"name": "Brown Dan"}]}, - {"name": "Wonder", "authors": [{"name": "Jun Murakami"}, {"name":"Craig Doe"}]}] -}]}'::json, '$.favorites[*]' -COLUMNS ( - user_id FOR ORDINALITY, - NESTED '$.movies[*]' - COLUMNS ( - movie_id FOR ORDINALITY, - mname text PATH '$.name', - director text), - NESTED '$.books[*]' - COLUMNS ( - book_id FOR ORDINALITY, - bname text PATH '$.name', - NESTED '$.authors[*]' - COLUMNS ( - author_id FOR ORDINALITY, - author_name text PATH '$.name')))); - - - - user_id | movie_id | mname | director | book_id | bname | author_id | author_name ----------+----------+-------+----------+---------+---------+-----------+-------------- - 1 | 1 | One | John Doe | | | | - 1 | 2 | Two | Don Joe | | | | - 1 | | | | 1 | Mystery | 1 | Brown Dan - 1 | | | | 2 | Wonder | 1 | Jun Murakami - 1 | | | | 2 | Wonder | 2 | Craig Doe -(5 rows) - - - - - - - - Sequence Manipulation Functions - - - sequence - - - - This section describes functions for operating on sequence - objects, also called sequence generators or just sequences. - Sequence objects are special single-row tables created with . - Sequence objects are commonly used to generate unique identifiers - for rows of a table. The sequence functions, listed in , provide simple, multiuser-safe - methods for obtaining successive sequence values from sequence - objects. - - - - Sequence Functions - - - - - Function - - - Description - - - - - - - - - nextval - - nextval ( regclass ) - bigint - - - Advances the sequence object to its next value and returns that value. - This is done atomically: even if multiple sessions - execute nextval concurrently, each will safely - receive a distinct sequence value. - If the sequence object has been created with default parameters, - successive nextval calls will return successive - values beginning with 1. Other behaviors can be obtained by using - appropriate parameters in the - command. - - - This function requires USAGE - or UPDATE privilege on the sequence. - - - - - - - setval - - setval ( regclass, bigint , boolean ) - bigint - - - Sets the sequence object's current value, and optionally - its is_called flag. The two-parameter - form sets the sequence's last_value field to the - specified value and sets its is_called field to - true, meaning that the next - nextval will advance the sequence before - returning a value. The value that will be reported - by currval is also set to the specified value. - In the three-parameter form, is_called can be set - to either true - or false. true has the same - effect as the two-parameter form. If it is set - to false, the next nextval - will return exactly the specified value, and sequence advancement - commences with the following nextval. - Furthermore, the value reported by currval is not - changed in this case. For example, - -SELECT setval('myseq', 42); Next nextval will return 43 -SELECT setval('myseq', 42, true); Same as above -SELECT setval('myseq', 42, false); Next nextval will return 42 - - The result returned by setval is just the value of its - second argument. - - - This function requires UPDATE privilege on the - sequence. - - - - - - - currval - - currval ( regclass ) - bigint - - - Returns the value most recently obtained - by nextval for this sequence in the current - session. (An error is reported if nextval has - never been called for this sequence in this session.) Because this is - returning a session-local value, it gives a predictable answer whether - or not other sessions have executed nextval since - the current session did. - - - This function requires USAGE - or SELECT privilege on the sequence. - - - - - - - lastval - - lastval () - bigint - - - Returns the value most recently returned by - nextval in the current session. This function is - identical to currval, except that instead - of taking the sequence name as an argument it refers to whichever - sequence nextval was most recently applied to - in the current session. It is an error to call - lastval if nextval - has not yet been called in the current session. - - - This function requires USAGE - or SELECT privilege on the last used sequence. - - - - -

- - - - To avoid blocking concurrent transactions that obtain numbers from - the same sequence, the value obtained by nextval - is not reclaimed for re-use if the calling transaction later aborts. - This means that transaction aborts or database crashes can result in - gaps in the sequence of assigned values. That can happen without a - transaction abort, too. For example an INSERT with - an ON CONFLICT clause will compute the to-be-inserted - tuple, including doing any required nextval - calls, before detecting any conflict that would cause it to follow - the ON CONFLICT rule instead. - Thus, PostgreSQL sequence - objects cannot be used to obtain gapless - sequences. - - - - Likewise, sequence state changes made by setval - are immediately visible to other transactions, and are not undone if - the calling transaction rolls back. - - - - If the database cluster crashes before committing a transaction - containing a nextval - or setval call, the sequence state change might - not have made its way to persistent storage, so that it is uncertain - whether the sequence will have its original or updated state after the - cluster restarts. This is harmless for usage of the sequence within - the database, since other effects of uncommitted transactions will not - be visible either. However, if you wish to use a sequence value for - persistent outside-the-database purposes, make sure that the - nextval call has been committed before doing so. - - - - - The sequence to be operated on by a sequence function is specified by - a regclass argument, which is simply the OID of the sequence in the - pg_class system catalog. You do not have to look up the - OID by hand, however, since the regclass data type's input - converter will do the work for you. See - for details. - - - - - - Conditional Expressions - - - CASE - - - - conditional expression - - - - This section describes the SQL-compliant conditional expressions - available in PostgreSQL. - - - - - If your needs go beyond the capabilities of these conditional - expressions, you might want to consider writing a server-side function - in a more expressive programming language. - - - - - - Although COALESCE, GREATEST, and - LEAST are syntactically similar to functions, they are - not ordinary functions, and thus cannot be used with explicit - VARIADIC array arguments. - - - - - <literal>CASE</literal> - - - The SQL CASE expression is a - generic conditional expression, similar to if/else statements in - other programming languages: - - -CASE WHEN condition THEN result - WHEN ... - ELSE result -END - - - CASE clauses can be used wherever - an expression is valid. Each condition is an - expression that returns a boolean result. If the condition's - result is true, the value of the CASE expression is the - result that follows the condition, and the - remainder of the CASE expression is not processed. If the - condition's result is not true, any subsequent WHEN clauses - are examined in the same manner. If no WHEN - condition yields true, the value of the - CASE expression is the result of the - ELSE clause. If the ELSE clause is - omitted and no condition is true, the result is null. - - - - An example: - -SELECT * FROM test; - - a ---- - 1 - 2 - 3 - - -SELECT a, - CASE WHEN a=1 THEN 'one' - WHEN a=2 THEN 'two' - ELSE 'other' - END - FROM test; - - a | case ----+------- - 1 | one - 2 | two - 3 | other - - - - - The data types of all the result - expressions must be convertible to a single output type. - See for more details. - - - - There is a simple form of CASE expression - that is a variant of the general form above: - - -CASE expression - WHEN value THEN result - WHEN ... - ELSE result -END - - - The first - expression is computed, then compared to - each of the value expressions in the - WHEN clauses until one is found that is equal to it. If - no match is found, the result of the - ELSE clause (or a null value) is returned. This is similar - to the switch statement in C. - - - - The example above can be written using the simple - CASE syntax: - -SELECT a, - CASE a WHEN 1 THEN 'one' - WHEN 2 THEN 'two' - ELSE 'other' - END - FROM test; - - a | case ----+------- - 1 | one - 2 | two - 3 | other - - - - - A CASE expression does not evaluate any subexpressions - that are not needed to determine the result. For example, this is a - possible way of avoiding a division-by-zero failure: - -SELECT ... WHERE CASE WHEN x <> 0 THEN y/x > 1.5 ELSE false END; - - - - - - As described in , there are various - situations in which subexpressions of an expression are evaluated at - different times, so that the principle that CASE - evaluates only necessary subexpressions is not ironclad. For - example a constant 1/0 subexpression will usually result in - a division-by-zero failure at planning time, even if it's within - a CASE arm that would never be entered at run time. - - - - - - <literal>COALESCE</literal> - - - COALESCE - - - - NVL - - - - IFNULL - - - -COALESCE(value , ...) - - - - The COALESCE function returns the first of its - arguments that is not null. Null is returned only if all arguments - are null. It is often used to substitute a default value for - null values when data is retrieved for display, for example: - -SELECT COALESCE(description, short_description, '(none)') ... - - This returns description if it is not null, otherwise - short_description if it is not null, otherwise (none). - - - - The arguments must all be convertible to a common data type, which - will be the type of the result (see - for details). - - - - Like a CASE expression, COALESCE only - evaluates the arguments that are needed to determine the result; - that is, arguments to the right of the first non-null argument are - not evaluated. This SQL-standard function provides capabilities similar - to NVL and IFNULL, which are used in some other - database systems. - - - - - <literal>NULLIF</literal> - - - NULLIF - - - -NULLIF(value1, value2) - - - - The NULLIF function returns a null value if - value1 equals value2; - otherwise it returns value1. - This can be used to perform the inverse operation of the - COALESCE example given above: - -SELECT NULLIF(value, '(none)') ... - - In this example, if value is (none), - null is returned, otherwise the value of value - is returned. - - - - The two arguments must be of comparable types. - To be specific, they are compared exactly as if you had - written value1 - = value2, so there must be a - suitable = operator available. - - - - The result has the same type as the first argument — but there is - a subtlety. What is actually returned is the first argument of the - implied = operator, and in some cases that will have - been promoted to match the second argument's type. For - example, NULLIF(1, 2.2) yields numeric, - because there is no integer = - numeric operator, - only numeric = numeric. - - - - - - <literal>GREATEST</literal> and <literal>LEAST</literal> - - - GREATEST - - - LEAST - - - -GREATEST(value , ...) - - -LEAST(value , ...) - - - - The GREATEST and LEAST functions select the - largest or smallest value from a list of any number of expressions. - The expressions must all be convertible to a common data type, which - will be the type of the result - (see for details). - - - - NULL values in the argument list are ignored. The result will be NULL - only if all the expressions evaluate to NULL. (This is a deviation from - the SQL standard. According to the standard, the return value is NULL if - any argument is NULL. Some other databases behave this way.) - - - - - - Array Functions and Operators - - - shows the specialized operators - available for array types. - In addition to those, the usual comparison operators shown in are available for - arrays. The comparison operators compare the array contents - element-by-element, using the default B-tree comparison function for - the element data type, and sort based on the first difference. - In multidimensional arrays the elements are visited in row-major order - (last subscript varies most rapidly). - If the contents of two arrays are equal but the dimensionality is - different, the first difference in the dimensionality information - determines the sort order. - - - - Array Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - anyarray @> anyarray - boolean - - - Does the first array contain the second, that is, does each element - appearing in the second array equal some element of the first array? - (Duplicates are not treated specially, - thus ARRAY[1] and ARRAY[1,1] are - each considered to contain the other.) - - - ARRAY[1,4,3] @> ARRAY[3,1,3] - t - - - - - - anyarray <@ anyarray - boolean - - - Is the first array contained by the second? - - - ARRAY[2,2,7] <@ ARRAY[1,7,4,2,6] - t - - - - - - anyarray && anyarray - boolean - - - Do the arrays overlap, that is, have any elements in common? - - - ARRAY[1,4,3] && ARRAY[2,1] - t - - - - - - anycompatiblearray || anycompatiblearray - anycompatiblearray - - - Concatenates the two arrays. Concatenating a null or empty array is a - no-op; otherwise the arrays must have the same number of dimensions - (as illustrated by the first example) or differ in number of - dimensions by one (as illustrated by the second). - If the arrays are not of identical element types, they will be coerced - to a common type (see ). - - - ARRAY[1,2,3] || ARRAY[4,5,6,7] - {1,2,3,4,5,6,7} - - - ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9.9]] - {{1,2,3},{4,5,6},{7,8,9.9}} - - - - - - anycompatible || anycompatiblearray - anycompatiblearray - - - Concatenates an element onto the front of an array (which must be - empty or one-dimensional). - - - 3 || ARRAY[4,5,6] - {3,4,5,6} - - - - - - anycompatiblearray || anycompatible - anycompatiblearray - - - Concatenates an element onto the end of an array (which must be - empty or one-dimensional). - - - ARRAY[4,5,6] || 7 - {4,5,6,7} - - - - -

- - - See for more details about array operator - behavior. See for more details about - which operators support indexed operations. - - - - shows the functions - available for use with array types. See - for more information and examples of the use of these functions. - - - - Array Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - array_append - - array_append ( anycompatiblearray, anycompatible ) - anycompatiblearray - - - Appends an element to the end of an array (same as - the anycompatiblearray || anycompatible - operator). - - - array_append(ARRAY[1,2], 3) - {1,2,3} - - - - - - - array_cat - - array_cat ( anycompatiblearray, anycompatiblearray ) - anycompatiblearray - - - Concatenates two arrays (same as - the anycompatiblearray || anycompatiblearray - operator). - - - array_cat(ARRAY[1,2,3], ARRAY[4,5]) - {1,2,3,4,5} - - - - - - - array_dims - - array_dims ( anyarray ) - text - - - Returns a text representation of the array's dimensions. - - - array_dims(ARRAY[[1,2,3], [4,5,6]]) - [1:2][1:3] - - - - - - - array_fill - - array_fill ( anyelement, integer[] - , integer[] ) - anyarray - - - Returns an array filled with copies of the given value, having - dimensions of the lengths specified by the second argument. - The optional third argument supplies lower-bound values for each - dimension (which default to all 1). - - - array_fill(11, ARRAY[2,3]) - {{11,11,11},{11,11,11}} - - - array_fill(7, ARRAY[3], ARRAY[2]) - [2:4]={7,7,7} - - - - - - - array_length - - array_length ( anyarray, integer ) - integer - - - Returns the length of the requested array dimension. - (Produces NULL instead of 0 for empty or missing array dimensions.) - - - array_length(array[1,2,3], 1) - 3 - - - array_length(array[]::int[], 1) - NULL - - - array_length(array['text'], 2) - NULL - - - - - - - array_lower - - array_lower ( anyarray, integer ) - integer - - - Returns the lower bound of the requested array dimension. - - - array_lower('[0:2]={1,2,3}'::integer[], 1) - 0 - - - - - - - array_ndims - - array_ndims ( anyarray ) - integer - - - Returns the number of dimensions of the array. - - - array_ndims(ARRAY[[1,2,3], [4,5,6]]) - 2 - - - - - - - array_position - - array_position ( anycompatiblearray, anycompatible , integer ) - integer - - - Returns the subscript of the first occurrence of the second argument - in the array, or NULL if it's not present. - If the third argument is given, the search begins at that subscript. - The array must be one-dimensional. - Comparisons are done using IS NOT DISTINCT FROM - semantics, so it is possible to search for NULL. - - - array_position(ARRAY['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'], 'mon') - 2 - - - - - - - array_positions - - array_positions ( anycompatiblearray, anycompatible ) - integer[] - - - Returns an array of the subscripts of all occurrences of the second - argument in the array given as first argument. - The array must be one-dimensional. - Comparisons are done using IS NOT DISTINCT FROM - semantics, so it is possible to search for NULL. - NULL is returned only if the array - is NULL; if the value is not found in the array, an - empty array is returned. - - - array_positions(ARRAY['A','A','B','A'], 'A') - {1,2,4} - - - - - - - array_prepend - - array_prepend ( anycompatible, anycompatiblearray ) - anycompatiblearray - - - Prepends an element to the beginning of an array (same as - the anycompatible || anycompatiblearray - operator). - - - array_prepend(1, ARRAY[2,3]) - {1,2,3} - - - - - - - array_remove - - array_remove ( anycompatiblearray, anycompatible ) - anycompatiblearray - - - Removes all elements equal to the given value from the array. - The array must be one-dimensional. - Comparisons are done using IS NOT DISTINCT FROM - semantics, so it is possible to remove NULLs. - - - array_remove(ARRAY[1,2,3,2], 2) - {1,3} - - - - - - - array_replace - - array_replace ( anycompatiblearray, anycompatible, anycompatible ) - anycompatiblearray - - - Replaces each array element equal to the second argument with the - third argument. - - - array_replace(ARRAY[1,2,5,4], 5, 3) - {1,2,3,4} - - - - - - - array_reverse - - array_reverse ( anyarray ) - anyarray - - - Reverses the first dimension of the array. - - - array_reverse(ARRAY[[1,2],[3,4],[5,6]]) - {{5,6},{3,4},{1,2}} - - - - - - - array_sample - - array_sample ( array anyarray, n integer ) - anyarray - - - Returns an array of n items randomly selected - from array. n may not - exceed the length of array's first dimension. - If array is multi-dimensional, - an item is a slice having a given first subscript. - - - array_sample(ARRAY[1,2,3,4,5,6], 3) - {2,6,1} - - - array_sample(ARRAY[[1,2],[3,4],[5,6]], 2) - {{5,6},{1,2}} - - - - - - - array_shuffle - - array_shuffle ( anyarray ) - anyarray - - - Randomly shuffles the first dimension of the array. - - - array_shuffle(ARRAY[[1,2],[3,4],[5,6]]) - {{5,6},{1,2},{3,4}} - - - - - - - array_sort - - array_sort ( - array anyarray - , descending boolean - , nulls_first boolean - ) - anyarray - - - Sorts the first dimension of the array. - The sort order is determined by the default sort ordering of the - array's element type; however, if the element type is collatable, - the collation to use can be specified by adding - a COLLATE clause to - the array argument. - - - If descending is true then sort in - descending order, otherwise ascending order. If omitted, the - default is ascending order. - If nulls_first is true then nulls appear - before non-null values, otherwise nulls appear after non-null - values. - If omitted, nulls_first is taken to have - the same value as descending. - - - array_sort(ARRAY[[2,4],[2,1],[6,5]]) - {{2,1},{2,4},{6,5}} - - - - - - - array_to_string - - array_to_string ( array anyarray, delimiter text , null_string text ) - text - - - Converts each array element to its text representation, and - concatenates those separated by - the delimiter string. - If null_string is given and is - not NULL, then NULL array - entries are represented by that string; otherwise, they are omitted. - See also string_to_array. - - - array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*') - 1,2,3,*,5 - - - - - - - array_upper - - array_upper ( anyarray, integer ) - integer - - - Returns the upper bound of the requested array dimension. - - - array_upper(ARRAY[1,8,3,7], 1) - 4 - - - - - - - cardinality - - cardinality ( anyarray ) - integer - - - Returns the total number of elements in the array, or 0 if the array - is empty. - - - cardinality(ARRAY[[1,2],[3,4]]) - 4 - - - - - - - trim_array - - trim_array ( array anyarray, n integer ) - anyarray - - - Trims an array by removing the last n elements. - If the array is multidimensional, only the first dimension is trimmed. - - - trim_array(ARRAY[1,2,3,4,5,6], 2) - {1,2,3,4} - - - - - - - unnest - - unnest ( anyarray ) - setof anyelement - - - Expands an array into a set of rows. - The array's elements are read out in storage order. - - - unnest(ARRAY[1,2]) - - - 1 - 2 - - - - unnest(ARRAY[['foo','bar'],['baz','quux']]) - - - foo - bar - baz - quux - - - - - - - unnest ( anyarray, anyarray , ... ) - setof anyelement, anyelement [, ... ] - - - Expands multiple arrays (possibly of different data types) into a set of - rows. If the arrays are not all the same length then the shorter ones - are padded with NULLs. This form is only allowed - in a query's FROM clause; see . - - - select * from unnest(ARRAY[1,2], ARRAY['foo','bar','baz']) as x(a,b) - - - a | b ----+----- - 1 | foo - 2 | bar - | baz - - - - - -

- - - See also about the aggregate - function array_agg for use with arrays. - - - - - Range/Multirange Functions and Operators - - - See for an overview of range types. - - - - shows the specialized operators - available for range types. - shows the specialized operators - available for multirange types. - In addition to those, the usual comparison operators shown in - are available for range - and multirange types. The comparison operators order first by the range lower - bounds, and only if those are equal do they compare the upper bounds. The - multirange operators compare each range until one is unequal. This - does not usually result in a useful overall ordering, but the operators are - provided to allow unique indexes to be constructed on ranges. - - - - Range Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - anyrange @> anyrange - boolean - - - Does the first range contain the second? - - - int4range(2,4) @> int4range(2,3) - t - - - - - - anyrange @> anyelement - boolean - - - Does the range contain the element? - - - '[2011-01-01,2011-03-01)'::tsrange @> '2011-01-10'::timestamp - t - - - - - - anyrange <@ anyrange - boolean - - - Is the first range contained by the second? - - - int4range(2,4) <@ int4range(1,7) - t - - - - - - anyelement <@ anyrange - boolean - - - Is the element contained in the range? - - - 42 <@ int4range(1,7) - f - - - - - - anyrange && anyrange - boolean - - - Do the ranges overlap, that is, have any elements in common? - - - int8range(3,7) && int8range(4,12) - t - - - - - - anyrange << anyrange - boolean - - - Is the first range strictly left of the second? - - - int8range(1,10) << int8range(100,110) - t - - - - - - anyrange >> anyrange - boolean - - - Is the first range strictly right of the second? - - - int8range(50,60) >> int8range(20,30) - t - - - - - - anyrange &< anyrange - boolean - - - Does the first range not extend to the right of the second? - - - int8range(1,20) &< int8range(18,20) - t - - - - - - anyrange &> anyrange - boolean - - - Does the first range not extend to the left of the second? - - - int8range(7,20) &> int8range(5,10) - t - - - - - - anyrange -|- anyrange - boolean - - - Are the ranges adjacent? - - - numrange(1.1,2.2) -|- numrange(2.2,3.3) - t - - - - - - anyrange + anyrange - anyrange - - - Computes the union of the ranges. The ranges must overlap or be - adjacent, so that the union is a single range (but - see range_merge()). - - - numrange(5,15) + numrange(10,20) - [5,20) - - - - - - anyrange * anyrange - anyrange - - - Computes the intersection of the ranges. - - - int8range(5,15) * int8range(10,20) - [10,15) - - - - - - anyrange - anyrange - anyrange - - - Computes the difference of the ranges. The second range must not be - contained in the first in such a way that the difference would not be - a single range. - - - int8range(5,15) - int8range(10,20) - [5,10) - - - - -

- - - Multirange Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - anymultirange @> anymultirange - boolean - - - Does the first multirange contain the second? - - - '{[2,4)}'::int4multirange @> '{[2,3)}'::int4multirange - t - - - - - - anymultirange @> anyrange - boolean - - - Does the multirange contain the range? - - - '{[2,4)}'::int4multirange @> int4range(2,3) - t - - - - - - anymultirange @> anyelement - boolean - - - Does the multirange contain the element? - - - '{[2011-01-01,2011-03-01)}'::tsmultirange @> '2011-01-10'::timestamp - t - - - - - - anyrange @> anymultirange - boolean - - - Does the range contain the multirange? - - - '[2,4)'::int4range @> '{[2,3)}'::int4multirange - t - - - - - - anymultirange <@ anymultirange - boolean - - - Is the first multirange contained by the second? - - - '{[2,4)}'::int4multirange <@ '{[1,7)}'::int4multirange - t - - - - - - anymultirange <@ anyrange - boolean - - - Is the multirange contained by the range? - - - '{[2,4)}'::int4multirange <@ int4range(1,7) - t - - - - - - anyrange <@ anymultirange - boolean - - - Is the range contained by the multirange? - - - int4range(2,4) <@ '{[1,7)}'::int4multirange - t - - - - - - anyelement <@ anymultirange - boolean - - - Is the element contained by the multirange? - - - 4 <@ '{[1,7)}'::int4multirange - t - - - - - - anymultirange && anymultirange - boolean - - - Do the multiranges overlap, that is, have any elements in common? - - - '{[3,7)}'::int8multirange && '{[4,12)}'::int8multirange - t - - - - - - anymultirange && anyrange - boolean - - - Does the multirange overlap the range? - - - '{[3,7)}'::int8multirange && int8range(4,12) - t - - - - - - anyrange && anymultirange - boolean - - - Does the range overlap the multirange? - - - int8range(3,7) && '{[4,12)}'::int8multirange - t - - - - - - anymultirange << anymultirange - boolean - - - Is the first multirange strictly left of the second? - - - '{[1,10)}'::int8multirange << '{[100,110)}'::int8multirange - t - - - - - - anymultirange << anyrange - boolean - - - Is the multirange strictly left of the range? - - - '{[1,10)}'::int8multirange << int8range(100,110) - t - - - - - - anyrange << anymultirange - boolean - - - Is the range strictly left of the multirange? - - - int8range(1,10) << '{[100,110)}'::int8multirange - t - - - - - - anymultirange >> anymultirange - boolean - - - Is the first multirange strictly right of the second? - - - '{[50,60)}'::int8multirange >> '{[20,30)}'::int8multirange - t - - - - - - anymultirange >> anyrange - boolean - - - Is the multirange strictly right of the range? - - - '{[50,60)}'::int8multirange >> int8range(20,30) - t - - - - - - anyrange >> anymultirange - boolean - - - Is the range strictly right of the multirange? - - - int8range(50,60) >> '{[20,30)}'::int8multirange - t - - - - - - anymultirange &< anymultirange - boolean - - - Does the first multirange not extend to the right of the second? - - - '{[1,20)}'::int8multirange &< '{[18,20)}'::int8multirange - t - - - - - - anymultirange &< anyrange - boolean - - - Does the multirange not extend to the right of the range? - - - '{[1,20)}'::int8multirange &< int8range(18,20) - t - - - - - - anyrange &< anymultirange - boolean - - - Does the range not extend to the right of the multirange? - - - int8range(1,20) &< '{[18,20)}'::int8multirange - t - - - - - - anymultirange &> anymultirange - boolean - - - Does the first multirange not extend to the left of the second? - - - '{[7,20)}'::int8multirange &> '{[5,10)}'::int8multirange - t - - - - - - anymultirange &> anyrange - boolean - - - Does the multirange not extend to the left of the range? - - - '{[7,20)}'::int8multirange &> int8range(5,10) - t - - - - - - anyrange &> anymultirange - boolean - - - Does the range not extend to the left of the multirange? - - - int8range(7,20) &> '{[5,10)}'::int8multirange - t - - - - - - anymultirange -|- anymultirange - boolean - - - Are the multiranges adjacent? - - - '{[1.1,2.2)}'::nummultirange -|- '{[2.2,3.3)}'::nummultirange - t - - - - - - anymultirange -|- anyrange - boolean - - - Is the multirange adjacent to the range? - - - '{[1.1,2.2)}'::nummultirange -|- numrange(2.2,3.3) - t - - - - - - anyrange -|- anymultirange - boolean - - - Is the range adjacent to the multirange? - - - numrange(1.1,2.2) -|- '{[2.2,3.3)}'::nummultirange - t - - - - - - anymultirange + anymultirange - anymultirange - - - Computes the union of the multiranges. The multiranges need not overlap - or be adjacent. - - - '{[5,10)}'::nummultirange + '{[15,20)}'::nummultirange - {[5,10), [15,20)} - - - - - - anymultirange * anymultirange - anymultirange - - - Computes the intersection of the multiranges. - - - '{[5,15)}'::int8multirange * '{[10,20)}'::int8multirange - {[10,15)} - - - - - - anymultirange - anymultirange - anymultirange - - - Computes the difference of the multiranges. - - - '{[5,20)}'::int8multirange - '{[10,15)}'::int8multirange - {[5,10), [15,20)} - - - - -

- - - The left-of/right-of/adjacent operators always return false when an empty - range or multirange is involved; that is, an empty range is not considered to - be either before or after any other range. - - - - Elsewhere empty ranges and multiranges are treated as the additive identity: - anything unioned with an empty value is itself. Anything minus an empty - value is itself. An empty multirange has exactly the same points as an empty - range. Every range contains the empty range. Every multirange contains as many - empty ranges as you like. - - - - The range union and difference operators will fail if the resulting range would - need to contain two disjoint sub-ranges, as such a range cannot be - represented. There are separate operators for union and difference that take - multirange parameters and return a multirange, and they do not fail even if - their arguments are disjoint. So if you need a union or difference operation - for ranges that may be disjoint, you can avoid errors by first casting your - ranges to multiranges. - - - - shows the functions - available for use with range types. - shows the functions - available for use with multirange types. - - - - Range Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - lower - - lower ( anyrange ) - anyelement - - - Extracts the lower bound of the range (NULL if the - range is empty or has no lower bound). - - - lower(numrange(1.1,2.2)) - 1.1 - - - - - - - upper - - upper ( anyrange ) - anyelement - - - Extracts the upper bound of the range (NULL if the - range is empty or has no upper bound). - - - upper(numrange(1.1,2.2)) - 2.2 - - - - - - - isempty - - isempty ( anyrange ) - boolean - - - Is the range empty? - - - isempty(numrange(1.1,2.2)) - f - - - - - - - lower_inc - - lower_inc ( anyrange ) - boolean - - - Is the range's lower bound inclusive? - - - lower_inc(numrange(1.1,2.2)) - t - - - - - - - upper_inc - - upper_inc ( anyrange ) - boolean - - - Is the range's upper bound inclusive? - - - upper_inc(numrange(1.1,2.2)) - f - - - - - - - lower_inf - - lower_inf ( anyrange ) - boolean - - - Does the range have no lower bound? (A lower bound of - -Infinity returns false.) - - - lower_inf('(,)'::daterange) - t - - - - - - - upper_inf - - upper_inf ( anyrange ) - boolean - - - Does the range have no upper bound? (An upper bound of - Infinity returns false.) - - - upper_inf('(,)'::daterange) - t - - - - - - - range_merge - - range_merge ( anyrange, anyrange ) - anyrange - - - Computes the smallest range that includes both of the given ranges. - - - range_merge('[1,2)'::int4range, '[3,4)'::int4range) - [1,4) - - - - -

- - - Multirange Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - lower - - lower ( anymultirange ) - anyelement - - - Extracts the lower bound of the multirange (NULL if the - multirange is empty or has no lower bound). - - - lower('{[1.1,2.2)}'::nummultirange) - 1.1 - - - - - - - upper - - upper ( anymultirange ) - anyelement - - - Extracts the upper bound of the multirange (NULL if the - multirange is empty or has no upper bound). - - - upper('{[1.1,2.2)}'::nummultirange) - 2.2 - - - - - - - isempty - - isempty ( anymultirange ) - boolean - - - Is the multirange empty? - - - isempty('{[1.1,2.2)}'::nummultirange) - f - - - - - - - lower_inc - - lower_inc ( anymultirange ) - boolean - - - Is the multirange's lower bound inclusive? - - - lower_inc('{[1.1,2.2)}'::nummultirange) - t - - - - - - - upper_inc - - upper_inc ( anymultirange ) - boolean - - - Is the multirange's upper bound inclusive? - - - upper_inc('{[1.1,2.2)}'::nummultirange) - f - - - - - - - lower_inf - - lower_inf ( anymultirange ) - boolean - - - Does the multirange have no lower bound? (A lower bound of - -Infinity returns false.) - - - lower_inf('{(,)}'::datemultirange) - t - - - - - - - upper_inf - - upper_inf ( anymultirange ) - boolean - - - Does the multirange have no upper bound? (An upper bound of - Infinity returns false.) - - - upper_inf('{(,)}'::datemultirange) - t - - - - - - - range_merge - - range_merge ( anymultirange ) - anyrange - - - Computes the smallest range that includes the entire multirange. - - - range_merge('{[1,2), [3,4)}'::int4multirange) - [1,4) - - - - - - - multirange (function) - - multirange ( anyrange ) - anymultirange - - - Returns a multirange containing just the given range. - - - multirange('[1,2)'::int4range) - {[1,2)} - - - - - - - unnest - for multirange - - unnest ( anymultirange ) - setof anyrange - - - Expands a multirange into a set of ranges in ascending order. - - - unnest('{[1,2), [3,4)}'::int4multirange) - - - [1,2) - [3,4) - - - - - -

- - - The lower_inc, upper_inc, - lower_inf, and upper_inf - functions all return false for an empty range or multirange. - - - - - Aggregate Functions - - - aggregate function - built-in - - - - Aggregate functions compute a single result - from a set of input values. The built-in general-purpose aggregate - functions are listed in - while statistical aggregates are in . - The built-in within-group ordered-set aggregate functions - are listed in - while the built-in within-group hypothetical-set ones are in . Grouping operations, - which are closely related to aggregate functions, are listed in - . - The special syntax considerations for aggregate - functions are explained in . - Consult for additional introductory - information. - - - - Aggregate functions that support Partial Mode - are eligible to participate in various optimizations, such as parallel - aggregation. - - - - While all aggregates below accept an optional - ORDER BY clause (as outlined in ), the clause has only been added to - aggregates whose output is affected by ordering. - - - - General-Purpose Aggregate Functions - - - - - - - Function - - - Description - - Partial Mode - - - - - - - - any_value - - any_value ( anyelement ) - same as input type - - - Returns an arbitrary value from the non-null input values. - - Yes - - - - - - array_agg - - array_agg ( anynonarray ORDER BY input_sort_columns ) - anyarray - - - Collects all the input values, including nulls, into an array. - - Yes - - - - - array_agg ( anyarray ORDER BY input_sort_columns ) - anyarray - - - Concatenates all the input arrays into an array of one higher - dimension. (The inputs must all have the same dimensionality, and - cannot be empty or null.) - - Yes - - - - - - average - - - avg - - avg ( smallint ) - numeric - - - avg ( integer ) - numeric - - - avg ( bigint ) - numeric - - - avg ( numeric ) - numeric - - - avg ( real ) - double precision - - - avg ( double precision ) - double precision - - - avg ( interval ) - interval - - - Computes the average (arithmetic mean) of all the non-null input - values. - - Yes - - - - - - bit_and - - bit_and ( smallint ) - smallint - - - bit_and ( integer ) - integer - - - bit_and ( bigint ) - bigint - - - bit_and ( bit ) - bit - - - Computes the bitwise AND of all non-null input values. - - Yes - - - - - - bit_or - - bit_or ( smallint ) - smallint - - - bit_or ( integer ) - integer - - - bit_or ( bigint ) - bigint - - - bit_or ( bit ) - bit - - - Computes the bitwise OR of all non-null input values. - - Yes - - - - - - bit_xor - - bit_xor ( smallint ) - smallint - - - bit_xor ( integer ) - integer - - - bit_xor ( bigint ) - bigint - - - bit_xor ( bit ) - bit - - - Computes the bitwise exclusive OR of all non-null input values. - Can be useful as a checksum for an unordered set of values. - - Yes - - - - - - bool_and - - bool_and ( boolean ) - boolean - - - Returns true if all non-null input values are true, otherwise false. - - Yes - - - - - - bool_or - - bool_or ( boolean ) - boolean - - - Returns true if any non-null input value is true, otherwise false. - - Yes - - - - - - count - - count ( * ) - bigint - - - Computes the number of input rows. - - Yes - - - - - count ( "any" ) - bigint - - - Computes the number of input rows in which the input value is not - null. - - Yes - - - - - - every - - every ( boolean ) - boolean - - - This is the SQL standard's equivalent to bool_and. - - Yes - - - - - - json_agg - - json_agg ( anyelement ORDER BY input_sort_columns ) - json - - - - jsonb_agg - - jsonb_agg ( anyelement ORDER BY input_sort_columns ) - jsonb - - - Collects all the input values, including nulls, into a JSON array. - Values are converted to JSON as per to_json - or to_jsonb. - - No - - - - - - json_agg_strict - - json_agg_strict ( anyelement ) - json - - - - jsonb_agg_strict - - jsonb_agg_strict ( anyelement ) - jsonb - - - Collects all the input values, skipping nulls, into a JSON array. - Values are converted to JSON as per to_json - or to_jsonb. - - No - - - - - json_arrayagg - json_arrayagg ( - value_expression - ORDER BY sort_expression - { NULL | ABSENT } ON NULL - RETURNING data_type FORMAT JSON ENCODING UTF8 ) - - - Behaves in the same way as json_array - but as an aggregate function so it only takes one - value_expression parameter. - If ABSENT ON NULL is specified, any NULL - values are omitted. - If ORDER BY is specified, the elements will - appear in the array in that order rather than in the input order. - - - SELECT json_arrayagg(v) FROM (VALUES(2),(1)) t(v) - [2, 1] - - No - - - - - json_objectagg - json_objectagg ( - { key_expression { VALUE | ':' } value_expression } - { NULL | ABSENT } ON NULL - { WITH | WITHOUT } UNIQUE KEYS - RETURNING data_type FORMAT JSON ENCODING UTF8 ) - - - Behaves like json_object, but as an - aggregate function, so it only takes one - key_expression and one - value_expression parameter. - - - SELECT json_objectagg(k:v) FROM (VALUES ('a'::text,current_date),('b',current_date + 1)) AS t(k,v) - { "a" : "2022-05-10", "b" : "2022-05-11" } - - No - - - - - - json_object_agg - - json_object_agg ( key - "any", value - "any" - ORDER BY input_sort_columns ) - json - - - - jsonb_object_agg - - jsonb_object_agg ( key - "any", value - "any" - ORDER BY input_sort_columns ) - jsonb - - - Collects all the key/value pairs into a JSON object. Key arguments - are coerced to text; value arguments are converted as per - to_json or to_jsonb. - Values can be null, but keys cannot. - - No - - - - - - json_object_agg_strict - - json_object_agg_strict ( - key "any", - value "any" ) - json - - - - jsonb_object_agg_strict - - jsonb_object_agg_strict ( - key "any", - value "any" ) - jsonb - - - Collects all the key/value pairs into a JSON object. Key arguments - are coerced to text; value arguments are converted as per - to_json or to_jsonb. - The key can not be null. If the - value is null then the entry is skipped, - - No - - - - - - json_object_agg_unique - - json_object_agg_unique ( - key "any", - value "any" ) - json - - - - jsonb_object_agg_unique - - jsonb_object_agg_unique ( - key "any", - value "any" ) - jsonb - - - Collects all the key/value pairs into a JSON object. Key arguments - are coerced to text; value arguments are converted as per - to_json or to_jsonb. - Values can be null, but keys cannot. - If there is a duplicate key an error is thrown. - - No - - - - - - json_object_agg_unique_strict - - json_object_agg_unique_strict ( - key "any", - value "any" ) - json - - - - jsonb_object_agg_unique_strict - - jsonb_object_agg_unique_strict ( - key "any", - value "any" ) - jsonb - - - Collects all the key/value pairs into a JSON object. Key arguments - are coerced to text; value arguments are converted as per - to_json or to_jsonb. - The key can not be null. If the - value is null then the entry is skipped. - If there is a duplicate key an error is thrown. - - No - - - - - - max - - max ( see text ) - same as input type - - - Computes the maximum of the non-null input - values. Available for any numeric, string, date/time, or enum type, - as well as bytea, inet, interval, - money, oid, pg_lsn, - tid, xid8, - and also arrays and composite types containing sortable data types. - - Yes - - - - - - min - - min ( see text ) - same as input type - - - Computes the minimum of the non-null input - values. Available for any numeric, string, date/time, or enum type, - as well as bytea, inet, interval, - money, oid, pg_lsn, - tid, xid8, - and also arrays and composite types containing sortable data types. - - Yes - - - - - - range_agg - - range_agg ( value - anyrange ) - anymultirange - - - range_agg ( value - anymultirange ) - anymultirange - - - Computes the union of the non-null input values. - - No - - - - - - range_intersect_agg - - range_intersect_agg ( value - anyrange ) - anyrange - - - range_intersect_agg ( value - anymultirange ) - anymultirange - - - Computes the intersection of the non-null input values. - - No - - - - - - string_agg - - string_agg ( value - text, delimiter text ) - text - - - string_agg ( value - bytea, delimiter bytea - ORDER BY input_sort_columns ) - bytea - - - Concatenates the non-null input values into a string. Each value - after the first is preceded by the - corresponding delimiter (if it's not null). - - Yes - - - - - - sum - - sum ( smallint ) - bigint - - - sum ( integer ) - bigint - - - sum ( bigint ) - numeric - - - sum ( numeric ) - numeric - - - sum ( real ) - real - - - sum ( double precision ) - double precision - - - sum ( interval ) - interval - - - sum ( money ) - money - - - Computes the sum of the non-null input values. - - Yes - - - - - - xmlagg - - xmlagg ( xml ORDER BY input_sort_columns ) - xml - - - Concatenates the non-null XML input values (see - ). - - No - - - -

- - - It should be noted that except for count, - these functions return a null value when no rows are selected. In - particular, sum of no rows returns null, not - zero as one might expect, and array_agg - returns null rather than an empty array when there are no input - rows. The coalesce function can be used to - substitute zero or an empty array for null when necessary. - - - - The aggregate functions array_agg, - json_agg, jsonb_agg, - json_agg_strict, jsonb_agg_strict, - json_object_agg, jsonb_object_agg, - json_object_agg_strict, jsonb_object_agg_strict, - json_object_agg_unique, jsonb_object_agg_unique, - json_object_agg_unique_strict, - jsonb_object_agg_unique_strict, - string_agg, - and xmlagg, as well as similar user-defined - aggregate functions, produce meaningfully different result values - depending on the order of the input values. This ordering is - unspecified by default, but can be controlled by writing an - ORDER BY clause within the aggregate call, as shown in - . - Alternatively, supplying the input values from a sorted subquery - will usually work. For example: - - - - Beware that this approach can fail if the outer query level contains - additional processing, such as a join, because that might cause the - subquery's output to be reordered before the aggregate is computed. - - - - - ANY - - - SOME - - - The boolean aggregates bool_and and - bool_or correspond to the standard SQL aggregates - every and any or - some. - PostgreSQL - supports every, but not any - or some, because there is an ambiguity built into - the standard syntax: - -SELECT b1 = ANY((SELECT b2 FROM t2 ...)) FROM t1 ...; - - Here ANY can be considered either as introducing - a subquery, or as being an aggregate function, if the subquery - returns one row with a Boolean value. - Thus the standard name cannot be given to these aggregates. - - - - - - Users accustomed to working with other SQL database management - systems might be disappointed by the performance of the - count aggregate when it is applied to the - entire table. A query like: - -SELECT count(*) FROM sometable; - - will require effort proportional to the size of the table: - PostgreSQL will need to scan either the - entire table or the entirety of an index that includes all rows in - the table. - - - - - shows - aggregate functions typically used in statistical analysis. - (These are separated out merely to avoid cluttering the listing - of more-commonly-used aggregates.) Functions shown as - accepting numeric_type are available for all - the types smallint, integer, - bigint, numeric, real, - and double precision. - Where the description mentions - N, it means the - number of input rows for which all the input expressions are non-null. - In all cases, null is returned if the computation is meaningless, - for example when N is zero. - - - - statistics - - - linear regression - - - - Aggregate Functions for Statistics - - - - - - - Function - - - Description - - Partial Mode - - - - - - - - correlation - - - corr - - corr ( Y double precision, X double precision ) - double precision - - - Computes the correlation coefficient. - - Yes - - - - - - covariance - population - - - covar_pop - - covar_pop ( Y double precision, X double precision ) - double precision - - - Computes the population covariance. - - Yes - - - - - - covariance - sample - - - covar_samp - - covar_samp ( Y double precision, X double precision ) - double precision - - - Computes the sample covariance. - - Yes - - - - - - regr_avgx - - regr_avgx ( Y double precision, X double precision ) - double precision - - - Computes the average of the independent variable, - sum(X)/N. - - Yes - - - - - - regr_avgy - - regr_avgy ( Y double precision, X double precision ) - double precision - - - Computes the average of the dependent variable, - sum(Y)/N. - - Yes - - - - - - regr_count - - regr_count ( Y double precision, X double precision ) - bigint - - - Computes the number of rows in which both inputs are non-null. - - Yes - - - - - - regression intercept - - - regr_intercept - - regr_intercept ( Y double precision, X double precision ) - double precision - - - Computes the y-intercept of the least-squares-fit linear equation - determined by the - (X, Y) pairs. - - Yes - - - - - - regr_r2 - - regr_r2 ( Y double precision, X double precision ) - double precision - - - Computes the square of the correlation coefficient. - - Yes - - - - - - regression slope - - - regr_slope - - regr_slope ( Y double precision, X double precision ) - double precision - - - Computes the slope of the least-squares-fit linear equation determined - by the (X, Y) - pairs. - - Yes - - - - - - regr_sxx - - regr_sxx ( Y double precision, X double precision ) - double precision - - - Computes the sum of squares of the independent - variable, - sum(X^2) - sum(X)^2/N. - - Yes - - - - - - regr_sxy - - regr_sxy ( Y double precision, X double precision ) - double precision - - - Computes the sum of products of independent times - dependent variables, - sum(X*Y) - sum(X) * sum(Y)/N. - - Yes - - - - - - regr_syy - - regr_syy ( Y double precision, X double precision ) - double precision - - - Computes the sum of squares of the dependent - variable, - sum(Y^2) - sum(Y)^2/N. - - Yes - - - - - - standard deviation - - - stddev - - stddev ( numeric_type ) - double precision - for real or double precision, - otherwise numeric - - - This is a historical alias for stddev_samp. - - Yes - - - - - - standard deviation - population - - - stddev_pop - - stddev_pop ( numeric_type ) - double precision - for real or double precision, - otherwise numeric - - - Computes the population standard deviation of the input values. - - Yes - - - - - - standard deviation - sample - - - stddev_samp - - stddev_samp ( numeric_type ) - double precision - for real or double precision, - otherwise numeric - - - Computes the sample standard deviation of the input values. - - Yes - - - - - - variance - - variance ( numeric_type ) - double precision - for real or double precision, - otherwise numeric - - - This is a historical alias for var_samp. - - Yes - - - - - - variance - population - - - var_pop - - var_pop ( numeric_type ) - double precision - for real or double precision, - otherwise numeric - - - Computes the population variance of the input values (square of the - population standard deviation). - - Yes - - - - - - variance - sample - - - var_samp - - var_samp ( numeric_type ) - double precision - for real or double precision, - otherwise numeric - - - Computes the sample variance of the input values (square of the sample - standard deviation). - - Yes - - - -

- - - shows some - aggregate functions that use the ordered-set aggregate - syntax. These functions are sometimes referred to as inverse - distribution functions. Their aggregated input is introduced by - ORDER BY, and they may also take a direct - argument that is not aggregated, but is computed only once. - All these functions ignore null values in their aggregated input. - For those that take a fraction parameter, the - fraction value must be between 0 and 1; an error is thrown if not. - However, a null fraction value simply produces a - null result. - - - - ordered-set aggregate - built-in - - - inverse distribution - - - - Ordered-Set Aggregate Functions - - - - - - - Function - - - Description - - Partial Mode - - - - - - - - mode - statistical - - mode () WITHIN GROUP ( ORDER BY anyelement ) - anyelement - - - Computes the mode, the most frequent - value of the aggregated argument (arbitrarily choosing the first one - if there are multiple equally-frequent values). The aggregated - argument must be of a sortable type. - - No - - - - - - percentile - continuous - - percentile_cont ( fraction double precision ) WITHIN GROUP ( ORDER BY double precision ) - double precision - - - percentile_cont ( fraction double precision ) WITHIN GROUP ( ORDER BY interval ) - interval - - - Computes the continuous percentile, a value - corresponding to the specified fraction - within the ordered set of aggregated argument values. This will - interpolate between adjacent input items if needed. - - No - - - - - percentile_cont ( fractions double precision[] ) WITHIN GROUP ( ORDER BY double precision ) - double precision[] - - - percentile_cont ( fractions double precision[] ) WITHIN GROUP ( ORDER BY interval ) - interval[] - - - Computes multiple continuous percentiles. The result is an array of - the same dimensions as the fractions - parameter, with each non-null element replaced by the (possibly - interpolated) value corresponding to that percentile. - - No - - - - - - percentile - discrete - - percentile_disc ( fraction double precision ) WITHIN GROUP ( ORDER BY anyelement ) - anyelement - - - Computes the discrete percentile, the first - value within the ordered set of aggregated argument values whose - position in the ordering equals or exceeds the - specified fraction. The aggregated - argument must be of a sortable type. - - No - - - - - percentile_disc ( fractions double precision[] ) WITHIN GROUP ( ORDER BY anyelement ) - anyarray - - - Computes multiple discrete percentiles. The result is an array of the - same dimensions as the fractions parameter, - with each non-null element replaced by the input value corresponding - to that percentile. - The aggregated argument must be of a sortable type. - - No - - - -

- - - hypothetical-set aggregate - built-in - - - - Each of the hypothetical-set aggregates listed in - is associated with a - window function of the same name defined in - . In each case, the aggregate's result - is the value that the associated window function would have - returned for the hypothetical row constructed from - args, if such a row had been added to the sorted - group of rows represented by the sorted_args. - For each of these functions, the list of direct arguments - given in args must match the number and types of - the aggregated arguments given in sorted_args. - Unlike most built-in aggregates, these aggregates are not strict, that is - they do not drop input rows containing nulls. Null values sort according - to the rule specified in the ORDER BY clause. - - - - Hypothetical-Set Aggregate Functions - - - - - - - Function - - - Description - - Partial Mode - - - - - - - - rank - hypothetical - - rank ( args ) WITHIN GROUP ( ORDER BY sorted_args ) - bigint - - - Computes the rank of the hypothetical row, with gaps; that is, the row - number of the first row in its peer group. - - No - - - - - - dense_rank - hypothetical - - dense_rank ( args ) WITHIN GROUP ( ORDER BY sorted_args ) - bigint - - - Computes the rank of the hypothetical row, without gaps; this function - effectively counts peer groups. - - No - - - - - - percent_rank - hypothetical - - percent_rank ( args ) WITHIN GROUP ( ORDER BY sorted_args ) - double precision - - - Computes the relative rank of the hypothetical row, that is - (rank - 1) / (total rows - 1). - The value thus ranges from 0 to 1 inclusive. - - No - - - - - - cume_dist - hypothetical - - cume_dist ( args ) WITHIN GROUP ( ORDER BY sorted_args ) - double precision - - - Computes the cumulative distribution, that is (number of rows - preceding or peers with hypothetical row) / (total rows). The value - thus ranges from 1/N to 1. - - No - - - -

- - - Grouping Operations - - - - - Function - - - Description - - - - - - - - - GROUPING - - GROUPING ( group_by_expression(s) ) - integer - - - Returns a bit mask indicating which GROUP BY - expressions are not included in the current grouping set. - Bits are assigned with the rightmost argument corresponding to the - least-significant bit; each bit is 0 if the corresponding expression - is included in the grouping criteria of the grouping set generating - the current result row, and 1 if it is not included. - - - - -

- - - The grouping operations shown in - are used in conjunction with - grouping sets (see ) to distinguish - result rows. The arguments to the GROUPING function - are not actually evaluated, but they must exactly match expressions given - in the GROUP BY clause of the associated query level. - For example: - -=> SELECT * FROM items_sold; - make | model | sales --------+-------+------- - Foo | GT | 10 - Foo | Tour | 20 - Bar | City | 15 - Bar | Sport | 5 -(4 rows) - -=> SELECT make, model, GROUPING(make,model), sum(sales) FROM items_sold GROUP BY ROLLUP(make,model); - make | model | grouping | sum --------+-------+----------+----- - Foo | GT | 0 | 10 - Foo | Tour | 0 | 20 - Bar | City | 0 | 15 - Bar | Sport | 0 | 5 - Foo | | 1 | 30 - Bar | | 1 | 20 - | | 3 | 50 -(7 rows) - - Here, the grouping value 0 in the - first four rows shows that those have been grouped normally, over both the - grouping columns. The value 1 indicates - that model was not grouped by in the next-to-last two - rows, and the value 3 indicates that - neither make nor model was grouped - by in the last row (which therefore is an aggregate over all the input - rows). - - - - - - Window Functions - - - window function - built-in - - - - Window functions provide the ability to perform - calculations across sets of rows that are related to the current query - row. See for an introduction to this - feature, and for syntax - details. - - - - The built-in window functions are listed in - . Note that these functions - must be invoked using window function syntax, i.e., an - OVER clause is required. - - - - In addition to these functions, any built-in or user-defined - ordinary aggregate (i.e., not ordered-set or hypothetical-set aggregates) - can be used as a window function; see - for a list of the built-in aggregates. - Aggregate functions act as window functions only when an OVER - clause follows the call; otherwise they act as plain aggregates - and return a single row for the entire set. - - - - General-Purpose Window Functions - - - - - Function - - - Description - - - - - - - - - row_number - - row_number () - bigint - - - Returns the number of the current row within its partition, counting - from 1. - - - - - - - rank - - rank () - bigint - - - Returns the rank of the current row, with gaps; that is, - the row_number of the first row in its peer - group. - - - - - - - dense_rank - - dense_rank () - bigint - - - Returns the rank of the current row, without gaps; this function - effectively counts peer groups. - - - - - - - percent_rank - - percent_rank () - double precision - - - Returns the relative rank of the current row, that is - (rank - 1) / (total partition rows - 1). - The value thus ranges from 0 to 1 inclusive. - - - - - - - cume_dist - - cume_dist () - double precision - - - Returns the cumulative distribution, that is (number of partition rows - preceding or peers with current row) / (total partition rows). - The value thus ranges from 1/N to 1. - - - - - - - ntile - - ntile ( num_buckets integer ) - integer - - - Returns an integer ranging from 1 to the argument value, dividing the - partition as equally as possible. - - - - - - - lag - - lag ( value anycompatible - , offset integer - , default anycompatible ) - anycompatible - - - Returns value evaluated at - the row that is offset - rows before the current row within the partition; if there is no such - row, instead returns default - (which must be of a type compatible with - value). - Both offset and - default are evaluated - with respect to the current row. If omitted, - offset defaults to 1 and - default to NULL. - - - - - - - lead - - lead ( value anycompatible - , offset integer - , default anycompatible ) - anycompatible - - - Returns value evaluated at - the row that is offset - rows after the current row within the partition; if there is no such - row, instead returns default - (which must be of a type compatible with - value). - Both offset and - default are evaluated - with respect to the current row. If omitted, - offset defaults to 1 and - default to NULL. - - - - - - - first_value - - first_value ( value anyelement ) - anyelement - - - Returns value evaluated - at the row that is the first row of the window frame. - - - - - - - last_value - - last_value ( value anyelement ) - anyelement - - - Returns value evaluated - at the row that is the last row of the window frame. - - - - - - - nth_value - - nth_value ( value anyelement, n integer ) - anyelement - - - Returns value evaluated - at the row that is the n'th - row of the window frame (counting from 1); - returns NULL if there is no such row. - - - - -

- - - All of the functions listed in - depend on the sort ordering - specified by the ORDER BY clause of the associated window - definition. Rows that are not distinct when considering only the - ORDER BY columns are said to be peers. - The four ranking functions (including cume_dist) are - defined so that they give the same answer for all rows of a peer group. - - - - Note that first_value, last_value, and - nth_value consider only the rows within the window - frame, which by default contains the rows from the start of the - partition through the last peer of the current row. This is - likely to give unhelpful results for last_value and - sometimes also nth_value. You can redefine the frame by - adding a suitable frame specification (RANGE, - ROWS or GROUPS) to - the OVER clause. - See for more information - about frame specifications. - - - - When an aggregate function is used as a window function, it aggregates - over the rows within the current row's window frame. - An aggregate used with ORDER BY and the default window frame - definition produces a running sum type of behavior, which may or - may not be what's wanted. To obtain - aggregation over the whole partition, omit ORDER BY or use - ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING. - Other frame specifications can be used to obtain other effects. - - - - - The SQL standard defines a RESPECT NULLS or - IGNORE NULLS option for lead, lag, - first_value, last_value, and - nth_value. This is not implemented in - PostgreSQL: the behavior is always the - same as the standard's default, namely RESPECT NULLS. - Likewise, the standard's FROM FIRST or FROM LAST - option for nth_value is not implemented: only the - default FROM FIRST behavior is supported. (You can achieve - the result of FROM LAST by reversing the ORDER BY - ordering.) - - - - - - - Merge Support Functions - - - MERGE - RETURNING - - - - PostgreSQL includes one merge support function - that may be used in the RETURNING list of a - command to identify the action taken for each - row; see . - - - - Merge Support Functions - - - - - - Function - - - Description - - - - - - - - - merge_action - - merge_action ( ) - text - - - Returns the merge action command executed for the current row. This - will be 'INSERT', 'UPDATE', or - 'DELETE'. - - - - -

- - - Example: - 0 THEN - UPDATE SET in_stock = true, quantity = s.quantity - WHEN MATCHED THEN - UPDATE SET in_stock = false, quantity = 0 - WHEN NOT MATCHED THEN - INSERT (product_id, in_stock, quantity) - VALUES (s.product_id, true, s.quantity) - RETURNING merge_action(), p.*; - - merge_action | product_id | in_stock | quantity ---------------+------------+----------+---------- - UPDATE | 1001 | t | 50 - UPDATE | 1002 | f | 0 - INSERT | 1003 | t | 10 -]]> - - - - Note that this function can only be used in the RETURNING - list of a MERGE command. It is an error to use it in any - other part of a query. - - - - - - Subquery Expressions - - - EXISTS - - - - IN - - - - NOT IN - - - - ANY - - - - ALL - - - - SOME - - - - subquery - - - - This section describes the SQL-compliant subquery - expressions available in PostgreSQL. - All of the expression forms documented in this section return - Boolean (true/false) results. - - - - <literal>EXISTS</literal> - - -EXISTS (subquery) - - - - The argument of EXISTS is an arbitrary SELECT statement, - or subquery. The - subquery is evaluated to determine whether it returns any rows. - If it returns at least one row, the result of EXISTS is - true; if the subquery returns no rows, the result of EXISTS - is false. - - - - The subquery can refer to variables from the surrounding query, - which will act as constants during any one evaluation of the subquery. - - - - The subquery will generally only be executed long enough to determine - whether at least one row is returned, not all the way to completion. - It is unwise to write a subquery that has side effects (such as - calling sequence functions); whether the side effects occur - might be unpredictable. - - - - Since the result depends only on whether any rows are returned, - and not on the contents of those rows, the output list of the - subquery is normally unimportant. A common coding convention is - to write all EXISTS tests in the form - EXISTS(SELECT 1 WHERE ...). There are exceptions to - this rule however, such as subqueries that use INTERSECT. - - - - This simple example is like an inner join on col2, but - it produces at most one output row for each tab1 row, - even if there are several matching tab2 rows: - -SELECT col1 -FROM tab1 -WHERE EXISTS (SELECT 1 FROM tab2 WHERE col2 = tab1.col2); - - - - - - <literal>IN</literal> - - -expression IN (subquery) - - - - The right-hand side is a parenthesized - subquery, which must return exactly one column. The left-hand expression - is evaluated and compared to each row of the subquery result. - The result of IN is true if any equal subquery row is found. - The result is false if no equal row is found (including the - case where the subquery returns no rows). - - - - Note that if the left-hand expression yields null, or if there are - no equal right-hand values and at least one right-hand row yields - null, the result of the IN construct will be null, not false. - This is in accordance with SQL's normal rules for Boolean combinations - of null values. - - - - As with EXISTS, it's unwise to assume that the subquery will - be evaluated completely. - - - -row_constructor IN (subquery) - - - - The left-hand side of this form of IN is a row constructor, - as described in . - The right-hand side is a parenthesized - subquery, which must return exactly as many columns as there are - expressions in the left-hand row. The left-hand expressions are - evaluated and compared row-wise to each row of the subquery result. - The result of IN is true if any equal subquery row is found. - The result is false if no equal row is found (including the - case where the subquery returns no rows). - - - - As usual, null values in the rows are combined per - the normal rules of SQL Boolean expressions. Two rows are considered - equal if all their corresponding members are non-null and equal; the rows - are unequal if any corresponding members are non-null and unequal; - otherwise the result of that row comparison is unknown (null). - If all the per-row results are either unequal or null, with at least one - null, then the result of IN is null. - - - - - <literal>NOT IN</literal> - - -expression NOT IN (subquery) - - - - The right-hand side is a parenthesized - subquery, which must return exactly one column. The left-hand expression - is evaluated and compared to each row of the subquery result. - The result of NOT IN is true if only unequal subquery rows - are found (including the case where the subquery returns no rows). - The result is false if any equal row is found. - - - - Note that if the left-hand expression yields null, or if there are - no equal right-hand values and at least one right-hand row yields - null, the result of the NOT IN construct will be null, not true. - This is in accordance with SQL's normal rules for Boolean combinations - of null values. - - - - As with EXISTS, it's unwise to assume that the subquery will - be evaluated completely. - - - -row_constructor NOT IN (subquery) - - - - The left-hand side of this form of NOT IN is a row constructor, - as described in . - The right-hand side is a parenthesized - subquery, which must return exactly as many columns as there are - expressions in the left-hand row. The left-hand expressions are - evaluated and compared row-wise to each row of the subquery result. - The result of NOT IN is true if only unequal subquery rows - are found (including the case where the subquery returns no rows). - The result is false if any equal row is found. - - - - As usual, null values in the rows are combined per - the normal rules of SQL Boolean expressions. Two rows are considered - equal if all their corresponding members are non-null and equal; the rows - are unequal if any corresponding members are non-null and unequal; - otherwise the result of that row comparison is unknown (null). - If all the per-row results are either unequal or null, with at least one - null, then the result of NOT IN is null. - - - - - <literal>ANY</literal>/<literal>SOME</literal> - - -expression operator ANY (subquery) -expression operator SOME (subquery) - - - - The right-hand side is a parenthesized - subquery, which must return exactly one column. The left-hand expression - is evaluated and compared to each row of the subquery result using the - given operator, which must yield a Boolean - result. - The result of ANY is true if any true result is obtained. - The result is false if no true result is found (including the - case where the subquery returns no rows). - - - - SOME is a synonym for ANY. - IN is equivalent to = ANY. - - - - Note that if there are no successes and at least one right-hand row yields - null for the operator's result, the result of the ANY construct - will be null, not false. - This is in accordance with SQL's normal rules for Boolean combinations - of null values. - - - - As with EXISTS, it's unwise to assume that the subquery will - be evaluated completely. - - - -row_constructor operator ANY (subquery) -row_constructor operator SOME (subquery) - - - - The left-hand side of this form of ANY is a row constructor, - as described in . - The right-hand side is a parenthesized - subquery, which must return exactly as many columns as there are - expressions in the left-hand row. The left-hand expressions are - evaluated and compared row-wise to each row of the subquery result, - using the given operator. - The result of ANY is true if the comparison - returns true for any subquery row. - The result is false if the comparison returns false for every - subquery row (including the case where the subquery returns no - rows). - The result is NULL if no comparison with a subquery row returns true, - and at least one comparison returns NULL. - - - - See for details about the meaning - of a row constructor comparison. - - - - - <literal>ALL</literal> - - -expression operator ALL (subquery) - - - - The right-hand side is a parenthesized - subquery, which must return exactly one column. The left-hand expression - is evaluated and compared to each row of the subquery result using the - given operator, which must yield a Boolean - result. - The result of ALL is true if all rows yield true - (including the case where the subquery returns no rows). - The result is false if any false result is found. - The result is NULL if no comparison with a subquery row returns false, - and at least one comparison returns NULL. - - - - NOT IN is equivalent to <> ALL. - - - - As with EXISTS, it's unwise to assume that the subquery will - be evaluated completely. - - - -row_constructor operator ALL (subquery) - - - - The left-hand side of this form of ALL is a row constructor, - as described in . - The right-hand side is a parenthesized - subquery, which must return exactly as many columns as there are - expressions in the left-hand row. The left-hand expressions are - evaluated and compared row-wise to each row of the subquery result, - using the given operator. - The result of ALL is true if the comparison - returns true for all subquery rows (including the - case where the subquery returns no rows). - The result is false if the comparison returns false for any - subquery row. - The result is NULL if no comparison with a subquery row returns false, - and at least one comparison returns NULL. - - - - See for details about the meaning - of a row constructor comparison. - - - - - Single-Row Comparison - - - comparison - subquery result row - - - -row_constructor operator (subquery) - - - - The left-hand side is a row constructor, - as described in . - The right-hand side is a parenthesized subquery, which must return exactly - as many columns as there are expressions in the left-hand row. Furthermore, - the subquery cannot return more than one row. (If it returns zero rows, - the result is taken to be null.) The left-hand side is evaluated and - compared row-wise to the single subquery result row. - - - - See for details about the meaning - of a row constructor comparison. - - - - - - - Row and Array Comparisons - - - IN - - - - NOT IN - - - - ANY - - - - ALL - - - - SOME - - - - composite type - comparison - - - - row-wise comparison - - - - comparison - composite type - - - - comparison - row constructor - - - - IS DISTINCT FROM - - - - IS NOT DISTINCT FROM - - - - This section describes several specialized constructs for making - multiple comparisons between groups of values. These forms are - syntactically related to the subquery forms of the previous section, - but do not involve subqueries. - The forms involving array subexpressions are - PostgreSQL extensions; the rest are - SQL-compliant. - All of the expression forms documented in this section return - Boolean (true/false) results. - - - - <literal>IN</literal> - - -expression IN (value , ...) - - - - The right-hand side is a parenthesized list - of expressions. The result is true if the left-hand expression's - result is equal to any of the right-hand expressions. This is a shorthand - notation for - - -expression = value1 -OR -expression = value2 -OR -... - - - - - Note that if the left-hand expression yields null, or if there are - no equal right-hand values and at least one right-hand expression yields - null, the result of the IN construct will be null, not false. - This is in accordance with SQL's normal rules for Boolean combinations - of null values. - - - - - <literal>NOT IN</literal> - - -expression NOT IN (value , ...) - - - - The right-hand side is a parenthesized list - of expressions. The result is true if the left-hand expression's - result is unequal to all of the right-hand expressions. This is a shorthand - notation for - - -expression <> value1 -AND -expression <> value2 -AND -... - - - - - Note that if the left-hand expression yields null, or if there are - no equal right-hand values and at least one right-hand expression yields - null, the result of the NOT IN construct will be null, not true - as one might naively expect. - This is in accordance with SQL's normal rules for Boolean combinations - of null values. - - - - - x NOT IN y is equivalent to NOT (x IN y) in all - cases. However, null values are much more likely to trip up the novice when - working with NOT IN than when working with IN. - It is best to express your condition positively if possible. - - - - - - <literal>ANY</literal>/<literal>SOME</literal> (array) - - -expression operator ANY (array expression) -expression operator SOME (array expression) - - - - The right-hand side is a parenthesized expression, which must yield an - array value. - The left-hand expression - is evaluated and compared to each element of the array using the - given operator, which must yield a Boolean - result. - The result of ANY is true if any true result is obtained. - The result is false if no true result is found (including the - case where the array has zero elements). - - - - If the array expression yields a null array, the result of - ANY will be null. If the left-hand expression yields null, - the result of ANY is ordinarily null (though a non-strict - comparison operator could possibly yield a different result). - Also, if the right-hand array contains any null elements and no true - comparison result is obtained, the result of ANY - will be null, not false (again, assuming a strict comparison operator). - This is in accordance with SQL's normal rules for Boolean combinations - of null values. - - - - SOME is a synonym for ANY. - - - - - <literal>ALL</literal> (array) - - -expression operator ALL (array expression) - - - - The right-hand side is a parenthesized expression, which must yield an - array value. - The left-hand expression - is evaluated and compared to each element of the array using the - given operator, which must yield a Boolean - result. - The result of ALL is true if all comparisons yield true - (including the case where the array has zero elements). - The result is false if any false result is found. - - - - If the array expression yields a null array, the result of - ALL will be null. If the left-hand expression yields null, - the result of ALL is ordinarily null (though a non-strict - comparison operator could possibly yield a different result). - Also, if the right-hand array contains any null elements and no false - comparison result is obtained, the result of ALL - will be null, not true (again, assuming a strict comparison operator). - This is in accordance with SQL's normal rules for Boolean combinations - of null values. - - - - - Row Constructor Comparison - - -row_constructor operator row_constructor - - - - Each side is a row constructor, - as described in . - The two row constructors must have the same number of fields. - The given operator is applied to each pair - of corresponding fields. (Since the fields could be of different - types, this means that a different specific operator could be selected - for each pair.) - All the selected operators must be members of some B-tree operator - class, or be the negator of an = member of a B-tree - operator class, meaning that row constructor comparison is only - possible when the operator is - =, - <>, - <, - <=, - >, or - >=, - or has semantics similar to one of these. - - - - The = and <> cases work slightly differently - from the others. Two rows are considered - equal if all their corresponding members are non-null and equal; the rows - are unequal if any corresponding members are non-null and unequal; - otherwise the result of the row comparison is unknown (null). - - - - For the <, <=, > and - >= cases, the row elements are compared left-to-right, - stopping as soon as an unequal or null pair of elements is found. - If either of this pair of elements is null, the result of the - row comparison is unknown (null); otherwise comparison of this pair - of elements determines the result. For example, - ROW(1,2,NULL) < ROW(1,3,0) - yields true, not null, because the third pair of elements are not - considered. - - - -row_constructor IS DISTINCT FROM row_constructor - - - - This construct is similar to a <> row comparison, - but it does not yield null for null inputs. Instead, any null value is - considered unequal to (distinct from) any non-null value, and any two - nulls are considered equal (not distinct). Thus the result will - either be true or false, never null. - - - -row_constructor IS NOT DISTINCT FROM row_constructor - - - - This construct is similar to a = row comparison, - but it does not yield null for null inputs. Instead, any null value is - considered unequal to (distinct from) any non-null value, and any two - nulls are considered equal (not distinct). Thus the result will always - be either true or false, never null. - - - - - - Composite Type Comparison - - -record operator record - - - - The SQL specification requires row-wise comparison to return NULL if the - result depends on comparing two NULL values or a NULL and a non-NULL. - PostgreSQL does this only when comparing the - results of two row constructors (as in - ) or comparing a row constructor - to the output of a subquery (as in ). - In other contexts where two composite-type values are compared, two - NULL field values are considered equal, and a NULL is considered larger - than a non-NULL. This is necessary in order to have consistent sorting - and indexing behavior for composite types. - - - - Each side is evaluated and they are compared row-wise. Composite type - comparisons are allowed when the operator is - =, - <>, - <, - <=, - > or - >=, - or has semantics similar to one of these. (To be specific, an operator - can be a row comparison operator if it is a member of a B-tree operator - class, or is the negator of the = member of a B-tree operator - class.) The default behavior of the above operators is the same as for - IS [ NOT ] DISTINCT FROM for row constructors (see - ). - - - - To support matching of rows which include elements without a default - B-tree operator class, the following operators are defined for composite - type comparison: - *=, - *<>, - *<, - *<=, - *>, and - *>=. - These operators compare the internal binary representation of the two - rows. Two rows might have a different binary representation even - though comparisons of the two rows with the equality operator is true. - The ordering of rows under these comparison operators is deterministic - but not otherwise meaningful. These operators are used internally - for materialized views and might be useful for other specialized - purposes such as replication and B-Tree deduplication (see ). They are not intended to be - generally useful for writing queries, though. - - - - - - Set Returning Functions - - - set returning functions - functions - - - - This section describes functions that possibly return more than one row. - The most widely used functions in this class are series generating - functions, as detailed in and - . Other, more specialized - set-returning functions are described elsewhere in this manual. - See for ways to combine multiple - set-returning functions. - - - - Series Generating Functions - - - - - Function - - - Description - - - - - - - - - generate_series - - generate_series ( start integer, stop integer , step integer ) - setof integer - - - generate_series ( start bigint, stop bigint , step bigint ) - setof bigint - - - generate_series ( start numeric, stop numeric , step numeric ) - setof numeric - - - Generates a series of values from start - to stop, with a step size - of step. step - defaults to 1. - - - - - - generate_series ( start timestamp, stop timestamp, step interval ) - setof timestamp - - - generate_series ( start timestamp with time zone, stop timestamp with time zone, step interval , timezone text ) - setof timestamp with time zone - - - Generates a series of values from start - to stop, with a step size - of step. - In the timezone-aware form, times of day and daylight-savings - adjustments are computed according to the time zone named by - the timezone argument, or the current - setting if that is omitted. - - - - -

- - - When step is positive, zero rows are returned if - start is greater than stop. - Conversely, when step is negative, zero rows are - returned if start is less than stop. - Zero rows are also returned if any input is NULL. - It is an error - for step to be zero. Some examples follow: - -SELECT * FROM generate_series(2,4); - generate_series ------------------ - 2 - 3 - 4 -(3 rows) - -SELECT * FROM generate_series(5,1,-2); - generate_series ------------------ - 5 - 3 - 1 -(3 rows) - -SELECT * FROM generate_series(4,3); - generate_series ------------------ -(0 rows) - -SELECT generate_series(1.1, 4, 1.3); - generate_series ------------------ - 1.1 - 2.4 - 3.7 -(3 rows) - --- this example relies on the date-plus-integer operator: -SELECT current_date + s.a AS dates FROM generate_series(0,14,7) AS s(a); - dates ------------- - 2004-02-05 - 2004-02-12 - 2004-02-19 -(3 rows) - -SELECT * FROM generate_series('2008-03-01 00:00'::timestamp, - '2008-03-04 12:00', '10 hours'); - generate_series ---------------------- - 2008-03-01 00:00:00 - 2008-03-01 10:00:00 - 2008-03-01 20:00:00 - 2008-03-02 06:00:00 - 2008-03-02 16:00:00 - 2008-03-03 02:00:00 - 2008-03-03 12:00:00 - 2008-03-03 22:00:00 - 2008-03-04 08:00:00 -(9 rows) - --- this example assumes that TimeZone is set to UTC; note the DST transition: -SELECT * FROM generate_series('2001-10-22 00:00 -04:00'::timestamptz, - '2001-11-01 00:00 -05:00'::timestamptz, - '1 day'::interval, 'America/New_York'); - generate_series ------------------------- - 2001-10-22 04:00:00+00 - 2001-10-23 04:00:00+00 - 2001-10-24 04:00:00+00 - 2001-10-25 04:00:00+00 - 2001-10-26 04:00:00+00 - 2001-10-27 04:00:00+00 - 2001-10-28 04:00:00+00 - 2001-10-29 05:00:00+00 - 2001-10-30 05:00:00+00 - 2001-10-31 05:00:00+00 - 2001-11-01 05:00:00+00 -(11 rows) - - - - - Subscript Generating Functions - - - - - Function - - - Description - - - - - - - - - generate_subscripts - - generate_subscripts ( array anyarray, dim integer ) - setof integer - - - Generates a series comprising the valid subscripts of - the dim'th dimension of the given array. - - - - - - generate_subscripts ( array anyarray, dim integer, reverse boolean ) - setof integer - - - Generates a series comprising the valid subscripts of - the dim'th dimension of the given array. - When reverse is true, returns the series in - reverse order. - - - - -

- - - generate_subscripts is a convenience function that generates - the set of valid subscripts for the specified dimension of the given - array. - Zero rows are returned for arrays that do not have the requested dimension, - or if any input is NULL. - Some examples follow: - --- basic usage: -SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1) AS s; - s ---- - 1 - 2 - 3 - 4 -(4 rows) - --- presenting an array, the subscript and the subscripted --- value requires a subquery: -SELECT * FROM arrays; - a --------------------- - {-1,-2} - {100,200,300} -(2 rows) - -SELECT a AS array, s AS subscript, a[s] AS value -FROM (SELECT generate_subscripts(a, 1) AS s, a FROM arrays) foo; - array | subscript | value ----------------+-----------+------- - {-1,-2} | 1 | -1 - {-1,-2} | 2 | -2 - {100,200,300} | 1 | 100 - {100,200,300} | 2 | 200 - {100,200,300} | 3 | 300 -(5 rows) - --- unnest a 2D array: -CREATE OR REPLACE FUNCTION unnest2(anyarray) -RETURNS SETOF anyelement AS $$ -select $1[i][j] - from generate_subscripts($1,1) g1(i), - generate_subscripts($1,2) g2(j); -$$ LANGUAGE sql IMMUTABLE; -CREATE FUNCTION -SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]); - unnest2 ---------- - 1 - 2 - 3 - 4 -(4 rows) - - - - - ordinality - - - - When a function in the FROM clause is suffixed - by WITH ORDINALITY, a bigint column is - appended to the function's output column(s), which starts from 1 and - increments by 1 for each row of the function's output. - This is most useful in the case of set returning - functions such as unnest(). - - --- set returning function WITH ORDINALITY: -SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n); - ls | n ------------------+---- - pg_serial | 1 - pg_twophase | 2 - postmaster.opts | 3 - pg_notify | 4 - postgresql.conf | 5 - pg_tblspc | 6 - logfile | 7 - base | 8 - postmaster.pid | 9 - pg_ident.conf | 10 - global | 11 - pg_xact | 12 - pg_snapshots | 13 - pg_multixact | 14 - PG_VERSION | 15 - pg_wal | 16 - pg_hba.conf | 17 - pg_stat_tmp | 18 - pg_subtrans | 19 -(19 rows) - - - - - - - System Information Functions and Operators - - - The functions described in this section are used to obtain various - information about a PostgreSQL installation. - - - - Session Information Functions - - - shows several - functions that extract session and system information. - - - - In addition to the functions listed in this section, there are a number of - functions related to the statistics system that also provide system - information. See for more - information. - - - - Session Information Functions - - - - - Function - - - Description - - - - - - - - - current_catalog - - current_catalog - name - - - - current_database - - current_database () - name - - - Returns the name of the current database. (Databases are - called catalogs in the SQL standard, - so current_catalog is the standard's - spelling.) - - - - - - - current_query - - current_query () - text - - - Returns the text of the currently executing query, as submitted - by the client (which might contain more than one statement). - - - - - - - current_role - - current_role - name - - - This is equivalent to current_user. - - - - - - - current_schema - - - schema - current - - current_schema - name - - - current_schema () - name - - - Returns the name of the schema that is first in the search path (or a - null value if the search path is empty). This is the schema that will - be used for any tables or other named objects that are created without - specifying a target schema. - - - - - - - current_schemas - - - search path - current - - current_schemas ( include_implicit boolean ) - name[] - - - Returns an array of the names of all schemas presently in the - effective search path, in their priority order. (Items in the current - setting that do not correspond to - existing, searchable schemas are omitted.) If the Boolean argument - is true, then implicitly-searched system schemas - such as pg_catalog are included in the result. - - - - - - - current_user - - - user - current - - current_user - name - - - Returns the user name of the current execution context. - - - - - - - inet_client_addr - - inet_client_addr () - inet - - - Returns the IP address of the current client, - or NULL if the current connection is via a - Unix-domain socket. - - - - - - - inet_client_port - - inet_client_port () - integer - - - Returns the IP port number of the current client, - or NULL if the current connection is via a - Unix-domain socket. - - - - - - - inet_server_addr - - inet_server_addr () - inet - - - Returns the IP address on which the server accepted the current - connection, - or NULL if the current connection is via a - Unix-domain socket. - - - - - - - inet_server_port - - inet_server_port () - integer - - - Returns the IP port number on which the server accepted the current - connection, - or NULL if the current connection is via a - Unix-domain socket. - - - - - - - pg_backend_pid - - pg_backend_pid () - integer - - - Returns the process ID of the server process attached to the current - session. - - - - - - - pg_blocking_pids - - pg_blocking_pids ( integer ) - integer[] - - - Returns an array of the process ID(s) of the sessions that are - blocking the server process with the specified process ID from - acquiring a lock, or an empty array if there is no such server process - or it is not blocked. - - - One server process blocks another if it either holds a lock that - conflicts with the blocked process's lock request (hard block), or is - waiting for a lock that would conflict with the blocked process's lock - request and is ahead of it in the wait queue (soft block). When using - parallel queries the result always lists client-visible process IDs - (that is, pg_backend_pid results) even if the - actual lock is held or awaited by a child worker process. As a result - of that, there may be duplicated PIDs in the result. Also note that - when a prepared transaction holds a conflicting lock, it will be - represented by a zero process ID. - - - Frequent calls to this function could have some impact on database - performance, because it needs exclusive access to the lock manager's - shared state for a short time. - - - - - - - pg_conf_load_time - - pg_conf_load_time () - timestamp with time zone - - - Returns the time when the server configuration files were last loaded. - If the current session was alive at the time, this will be the time - when the session itself re-read the configuration files (so the - reading will vary a little in different sessions). Otherwise it is - the time when the postmaster process re-read the configuration files. - - - - - - - pg_current_logfile - - - Logging - pg_current_logfile function - - - current_logfiles - and the pg_current_logfile function - - - Logging - current_logfiles file and the pg_current_logfile - function - - pg_current_logfile ( text ) - text - - - Returns the path name of the log file currently in use by the logging - collector. The path includes the - directory and the individual log file name. The result - is NULL if the logging collector is disabled. - When multiple log files exist, each in a different - format, pg_current_logfile without an argument - returns the path of the file having the first format found in the - ordered list: stderr, - csvlog, jsonlog. - NULL is returned if no log file has any of these - formats. - To request information about a specific log file format, supply - either csvlog, jsonlog or - stderr as the - value of the optional parameter. The result is NULL - if the log format requested is not configured in - . - The result reflects the contents of - the current_logfiles file. - - - This function is restricted to superusers and roles with privileges of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - pg_get_loaded_modules - - pg_get_loaded_modules () - setof record - ( module_name text, - version text, - file_name text ) - - - Returns a list of the loadable modules that are loaded into the - current server session. The module_name - and version fields are NULL unless the - module author supplied values for them using - the PG_MODULE_MAGIC_EXT macro. - The file_name field gives the file - name of the module (shared library). - - - - - - - pg_my_temp_schema - - pg_my_temp_schema () - oid - - - Returns the OID of the current session's temporary schema, or zero if - it has none (because it has not created any temporary tables). - - - - - - - pg_is_other_temp_schema - - pg_is_other_temp_schema ( oid ) - boolean - - - Returns true if the given OID is the OID of another session's - temporary schema. (This can be useful, for example, to exclude other - sessions' temporary tables from a catalog display.) - - - - - - - pg_jit_available - - pg_jit_available () - boolean - - - Returns true if a JIT compiler extension is - available (see ) and the - configuration parameter is set to - on. - - - - - - - pg_numa_available - - pg_numa_available () - boolean - - - Returns true if the server has been compiled with NUMA support. - - - - - - - pg_listening_channels - - pg_listening_channels () - setof text - - - Returns the set of names of asynchronous notification channels that - the current session is listening to. - - - - - - - pg_notification_queue_usage - - pg_notification_queue_usage () - double precision - - - Returns the fraction (0–1) of the asynchronous notification - queue's maximum size that is currently occupied by notifications that - are waiting to be processed. - See and - for more information. - - - - - - - pg_postmaster_start_time - - pg_postmaster_start_time () - timestamp with time zone - - - Returns the time when the server started. - - - - - - - pg_safe_snapshot_blocking_pids - - pg_safe_snapshot_blocking_pids ( integer ) - integer[] - - - Returns an array of the process ID(s) of the sessions that are blocking - the server process with the specified process ID from acquiring a safe - snapshot, or an empty array if there is no such server process or it - is not blocked. - - - A session running a SERIALIZABLE transaction blocks - a SERIALIZABLE READ ONLY DEFERRABLE transaction - from acquiring a snapshot until the latter determines that it is safe - to avoid taking any predicate locks. See - for more information about - serializable and deferrable transactions. - - - Frequent calls to this function could have some impact on database - performance, because it needs access to the predicate lock manager's - shared state for a short time. - - - - - - - pg_trigger_depth - - pg_trigger_depth () - integer - - - Returns the current nesting level - of PostgreSQL triggers (0 if not called, - directly or indirectly, from inside a trigger). - - - - - - - session_user - - session_user - name - - - Returns the session user's name. - - - - - - - system_user - - system_user - text - - - Returns the authentication method and the identity (if any) that the - user presented during the authentication cycle before they were - assigned a database role. It is represented as - auth_method:identity or - NULL if the user has not been authenticated (for - example if Trust authentication has - been used). - - - - - - - user - - user - name - - - This is equivalent to current_user. - - - - -

- - - - current_catalog, - current_role, - current_schema, - current_user, - session_user, - and user have special syntactic status - in SQL: they must be called without trailing - parentheses. In PostgreSQL, parentheses can optionally be used with - current_schema, but not with the others. - - - - - The session_user is normally the user who initiated - the current database connection; but superusers can change this setting - with . - The current_user is the user identifier - that is applicable for permission checking. Normally it is equal - to the session user, but it can be changed with - . - It also changes during the execution of - functions with the attribute SECURITY DEFINER. - In Unix parlance, the session user is the real user and - the current user is the effective user. - current_role and user are - synonyms for current_user. (The SQL standard draws - a distinction between current_role - and current_user, but PostgreSQL - does not, since it unifies users and roles into a single kind of entity.) - - - - - - Access Privilege Inquiry Functions - - - privilege - querying - - - - lists functions that - allow querying object access privileges programmatically. - (See for more information about - privileges.) - In these functions, the user whose privileges are being inquired about - can be specified by name or by OID - (pg_authid.oid), or if - the name is given as public then the privileges of the - PUBLIC pseudo-role are checked. Also, the user - argument can be omitted entirely, in which case - the current_user is assumed. - The object that is being inquired about can be specified either by name or - by OID, too. When specifying by name, a schema name can be included if - relevant. - The access privilege of interest is specified by a text string, which must - evaluate to one of the appropriate privilege keywords for the object's type - (e.g., SELECT). Optionally, WITH GRANT - OPTION can be added to a privilege type to test whether the - privilege is held with grant option. Also, multiple privilege types can be - listed separated by commas, in which case the result will be true if any of - the listed privileges is held. (Case of the privilege string is not - significant, and extra whitespace is allowed between but not within - privilege names.) - Some examples: - -SELECT has_table_privilege('myschema.mytable', 'select'); -SELECT has_table_privilege('joe', 'mytable', 'INSERT, SELECT WITH GRANT OPTION'); - - - - - Access Privilege Inquiry Functions - - - - - Function - - - Description - - - - - - - - - has_any_column_privilege - - has_any_column_privilege ( - user name or oid, - table text or oid, - privilege text ) - boolean - - - Does user have privilege for any column of table? - This succeeds either if the privilege is held for the whole table, or - if there is a column-level grant of the privilege for at least one - column. - Allowable privilege types are - SELECT, INSERT, - UPDATE, and REFERENCES. - - - - - - - has_column_privilege - - has_column_privilege ( - user name or oid, - table text or oid, - column text or smallint, - privilege text ) - boolean - - - Does user have privilege for the specified table column? - This succeeds either if the privilege is held for the whole table, or - if there is a column-level grant of the privilege for the column. - The column can be specified by name or by attribute number - (pg_attribute.attnum). - Allowable privilege types are - SELECT, INSERT, - UPDATE, and REFERENCES. - - - - - - - has_database_privilege - - has_database_privilege ( - user name or oid, - database text or oid, - privilege text ) - boolean - - - Does user have privilege for database? - Allowable privilege types are - CREATE, - CONNECT, - TEMPORARY, and - TEMP (which is equivalent to - TEMPORARY). - - - - - - - has_foreign_data_wrapper_privilege - - has_foreign_data_wrapper_privilege ( - user name or oid, - fdw text or oid, - privilege text ) - boolean - - - Does user have privilege for foreign-data wrapper? - The only allowable privilege type is USAGE. - - - - - - - has_function_privilege - - has_function_privilege ( - user name or oid, - function text or oid, - privilege text ) - boolean - - - Does user have privilege for function? - The only allowable privilege type is EXECUTE. - - - When specifying a function by name rather than by OID, the allowed - input is the same as for the regprocedure data type (see - ). - An example is: - -SELECT has_function_privilege('joeuser', 'myfunc(int, text)', 'execute'); - - - - - - - - has_language_privilege - - has_language_privilege ( - user name or oid, - language text or oid, - privilege text ) - boolean - - - Does user have privilege for language? - The only allowable privilege type is USAGE. - - - - - - - has_largeobject_privilege - - has_largeobject_privilege ( - user name or oid, - largeobject oid, - privilege text ) - boolean - - - Does user have privilege for large object? - Allowable privilege types are - SELECT and UPDATE. - - - - - - - has_parameter_privilege - - has_parameter_privilege ( - user name or oid, - parameter text, - privilege text ) - boolean - - - Does user have privilege for configuration parameter? - The parameter name is case-insensitive. - Allowable privilege types are SET - and ALTER SYSTEM. - - - - - - - has_schema_privilege - - has_schema_privilege ( - user name or oid, - schema text or oid, - privilege text ) - boolean - - - Does user have privilege for schema? - Allowable privilege types are - CREATE and - USAGE. - - - - - - - has_sequence_privilege - - has_sequence_privilege ( - user name or oid, - sequence text or oid, - privilege text ) - boolean - - - Does user have privilege for sequence? - Allowable privilege types are - USAGE, - SELECT, and - UPDATE. - - - - - - - has_server_privilege - - has_server_privilege ( - user name or oid, - server text or oid, - privilege text ) - boolean - - - Does user have privilege for foreign server? - The only allowable privilege type is USAGE. - - - - - - - has_table_privilege - - has_table_privilege ( - user name or oid, - table text or oid, - privilege text ) - boolean - - - Does user have privilege for table? - Allowable privilege types - are SELECT, INSERT, - UPDATE, DELETE, - TRUNCATE, REFERENCES, - TRIGGER, and MAINTAIN. - - - - - - - has_tablespace_privilege - - has_tablespace_privilege ( - user name or oid, - tablespace text or oid, - privilege text ) - boolean - - - Does user have privilege for tablespace? - The only allowable privilege type is CREATE. - - - - - - - has_type_privilege - - has_type_privilege ( - user name or oid, - type text or oid, - privilege text ) - boolean - - - Does user have privilege for data type? - The only allowable privilege type is USAGE. - When specifying a type by name rather than by OID, the allowed input - is the same as for the regtype data type (see - ). - - - - - - - pg_has_role - - pg_has_role ( - user name or oid, - role text or oid, - privilege text ) - boolean - - - Does user have privilege for role? - Allowable privilege types are - MEMBER, USAGE, - and SET. - MEMBER denotes direct or indirect membership in - the role without regard to what specific privileges may be conferred. - USAGE denotes whether the privileges of the role - are immediately available without doing SET ROLE, - while SET denotes whether it is possible to change - to the role using the SET ROLE command. - WITH ADMIN OPTION or WITH GRANT - OPTION can be added to any of these privilege types to - test whether the ADMIN privilege is held (all - six spellings test the same thing). - This function does not allow the special case of - setting user to public, - because the PUBLIC pseudo-role can never be a member of real roles. - - - - - - - row_security_active - - row_security_active ( - table text or oid ) - boolean - - - Is row-level security active for the specified table in the context of - the current user and current environment? - - - - -

- - - shows the operators - available for the aclitem type, which is the catalog - representation of access privileges. See - for information about how to read access privilege values. - - - - <type>aclitem</type> Operators - - - - - Operator - - - Description - - - Example(s) - - - - - - - - - aclitemeq - - aclitem = aclitem - boolean - - - Are aclitems equal? (Notice that - type aclitem lacks the usual set of comparison - operators; it has only equality. In turn, aclitem - arrays can only be compared for equality.) - - - 'calvin=r*w/hobbes'::aclitem = 'calvin=r*w*/hobbes'::aclitem - f - - - - - - - aclcontains - - aclitem[] @> aclitem - boolean - - - Does array contain the specified privileges? (This is true if there - is an array entry that matches the aclitem's grantee and - grantor, and has at least the specified set of privileges.) - - - '{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] @> 'calvin=r*/hobbes'::aclitem - t - - - - - - aclitem[] ~ aclitem - boolean - - - This is a deprecated alias for @>. - - - '{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] ~ 'calvin=r*/hobbes'::aclitem - t - - - - -

- - - shows some additional - functions to manage the aclitem type. - - - - <type>aclitem</type> Functions - - - - - Function - - - Description - - - - - - - - - acldefault - - acldefault ( - type "char", - ownerId oid ) - aclitem[] - - - Constructs an aclitem array holding the default access - privileges for an object of type type belonging - to the role with OID ownerId. This represents - the access privileges that will be assumed when an object's - ACL entry is null. (The default access privileges - are described in .) - The type parameter must be one of - 'c' for COLUMN, - 'r' for TABLE and table-like objects, - 's' for SEQUENCE, - 'd' for DATABASE, - 'f' for FUNCTION or PROCEDURE, - 'l' for LANGUAGE, - 'L' for LARGE OBJECT, - 'n' for SCHEMA, - 'p' for PARAMETER, - 't' for TABLESPACE, - 'F' for FOREIGN DATA WRAPPER, - 'S' for FOREIGN SERVER, - or - 'T' for TYPE or DOMAIN. - - - - - - - aclexplode - - aclexplode ( aclitem[] ) - setof record - ( grantor oid, - grantee oid, - privilege_type text, - is_grantable boolean ) - - - Returns the aclitem array as a set of rows. - If the grantee is the pseudo-role PUBLIC, it is represented by zero in - the grantee column. Each granted privilege is - represented as SELECT, INSERT, - etc (see for a full list). - Note that each privilege is broken out as a separate row, so - only one keyword appears in the privilege_type - column. - - - - - - - makeaclitem - - makeaclitem ( - grantee oid, - grantor oid, - privileges text, - is_grantable boolean ) - aclitem - - - Constructs an aclitem with the given properties. - privileges is a comma-separated list of - privilege names such as SELECT, - INSERT, etc, all of which are set in the - result. (Case of the privilege string is not significant, and - extra whitespace is allowed between but not within privilege - names.) - - - - -

- - - - - Schema Visibility Inquiry Functions - - - shows functions that - determine whether a certain object is visible in the - current schema search path. - For example, a table is said to be visible if its - containing schema is in the search path and no table of the same - name appears earlier in the search path. This is equivalent to the - statement that the table can be referenced by name without explicit - schema qualification. Thus, to list the names of all visible tables: - -SELECT relname FROM pg_class WHERE pg_table_is_visible(oid); - - For functions and operators, an object in the search path is said to be - visible if there is no object of the same name and argument data - type(s) earlier in the path. For operator classes and families, - both the name and the associated index access method are considered. - - - - search path - object visibility - - - - Schema Visibility Inquiry Functions - - - - - Function - - - Description - - - - - - - - - pg_collation_is_visible - - pg_collation_is_visible ( collation oid ) - boolean - - - Is collation visible in search path? - - - - - - - pg_conversion_is_visible - - pg_conversion_is_visible ( conversion oid ) - boolean - - - Is conversion visible in search path? - - - - - - - pg_function_is_visible - - pg_function_is_visible ( function oid ) - boolean - - - Is function visible in search path? - (This also works for procedures and aggregates.) - - - - - - - pg_opclass_is_visible - - pg_opclass_is_visible ( opclass oid ) - boolean - - - Is operator class visible in search path? - - - - - - - pg_operator_is_visible - - pg_operator_is_visible ( operator oid ) - boolean - - - Is operator visible in search path? - - - - - - - pg_opfamily_is_visible - - pg_opfamily_is_visible ( opclass oid ) - boolean - - - Is operator family visible in search path? - - - - - - - pg_statistics_obj_is_visible - - pg_statistics_obj_is_visible ( stat oid ) - boolean - - - Is statistics object visible in search path? - - - - - - - pg_table_is_visible - - pg_table_is_visible ( table oid ) - boolean - - - Is table visible in search path? - (This works for all types of relations, including views, materialized - views, indexes, sequences and foreign tables.) - - - - - - - pg_ts_config_is_visible - - pg_ts_config_is_visible ( config oid ) - boolean - - - Is text search configuration visible in search path? - - - - - - - pg_ts_dict_is_visible - - pg_ts_dict_is_visible ( dict oid ) - boolean - - - Is text search dictionary visible in search path? - - - - - - - pg_ts_parser_is_visible - - pg_ts_parser_is_visible ( parser oid ) - boolean - - - Is text search parser visible in search path? - - - - - - - pg_ts_template_is_visible - - pg_ts_template_is_visible ( template oid ) - boolean - - - Is text search template visible in search path? - - - - - - - pg_type_is_visible - - pg_type_is_visible ( type oid ) - boolean - - - Is type (or domain) visible in search path? - - - - -

- - - All these functions require object OIDs to identify the object to be - checked. If you want to test an object by name, it is convenient to use - the OID alias types (regclass, regtype, - regprocedure, regoperator, regconfig, - or regdictionary), - for example: - -SELECT pg_type_is_visible('myschema.widget'::regtype); - - Note that it would not make much sense to test a non-schema-qualified - type name in this way — if the name can be recognized at all, it must be visible. - - - - - - System Catalog Information Functions - - - lists functions that - extract information from the system catalogs. - - - - System Catalog Information Functions - - - - - Function - - - Description - - - - - - - - - format_type - - format_type ( type oid, typemod integer ) - text - - - Returns the SQL name for a data type that is identified by its type - OID and possibly a type modifier. Pass NULL for the type modifier if - no specific modifier is known. - - - - - - - pg_basetype - - pg_basetype ( regtype ) - regtype - - - Returns the OID of the base type of a domain identified by its - type OID. If the argument is the OID of a non-domain type, - returns the argument as-is. Returns NULL if the argument is - not a valid type OID. If there's a chain of domain dependencies, - it will recurse until finding the base type. - - - Assuming CREATE DOMAIN mytext AS text: - - - pg_basetype('mytext'::regtype) - text - - - - - - - pg_char_to_encoding - - pg_char_to_encoding ( encoding name ) - integer - - - Converts the supplied encoding name into an integer representing the - internal identifier used in some system catalog tables. - Returns -1 if an unknown encoding name is provided. - - - - - - - pg_encoding_to_char - - pg_encoding_to_char ( encoding integer ) - name - - - Converts the integer used as the internal identifier of an encoding in some - system catalog tables into a human-readable string. - Returns an empty string if an invalid encoding number is provided. - - - - - - - pg_get_catalog_foreign_keys - - pg_get_catalog_foreign_keys () - setof record - ( fktable regclass, - fkcols text[], - pktable regclass, - pkcols text[], - is_array boolean, - is_opt boolean ) - - - Returns a set of records describing the foreign key relationships - that exist within the PostgreSQL system - catalogs. - The fktable column contains the name of the - referencing catalog, and the fkcols column - contains the name(s) of the referencing column(s). Similarly, - the pktable column contains the name of the - referenced catalog, and the pkcols column - contains the name(s) of the referenced column(s). - If is_array is true, the last referencing - column is an array, each of whose elements should match some entry - in the referenced catalog. - If is_opt is true, the referencing column(s) - are allowed to contain zeroes instead of a valid reference. - - - - - - - pg_get_constraintdef - - pg_get_constraintdef ( constraint oid , pretty boolean ) - text - - - Reconstructs the creating command for a constraint. - (This is a decompiled reconstruction, not the original text - of the command.) - - - - - - - pg_get_expr - - pg_get_expr ( expr pg_node_tree, relation oid , pretty boolean ) - text - - - Decompiles the internal form of an expression stored in the system - catalogs, such as the default value for a column. If the expression - might contain Vars, specify the OID of the relation they refer to as - the second parameter; if no Vars are expected, passing zero is - sufficient. - - - - - - - pg_get_functiondef - - pg_get_functiondef ( func oid ) - text - - - Reconstructs the creating command for a function or procedure. - (This is a decompiled reconstruction, not the original text - of the command.) - The result is a complete CREATE OR REPLACE FUNCTION - or CREATE OR REPLACE PROCEDURE statement. - - - - - - - pg_get_function_arguments - - pg_get_function_arguments ( func oid ) - text - - - Reconstructs the argument list of a function or procedure, in the form - it would need to appear in within CREATE FUNCTION - (including default values). - - - - - - - pg_get_function_identity_arguments - - pg_get_function_identity_arguments ( func oid ) - text - - - Reconstructs the argument list necessary to identify a function or - procedure, in the form it would need to appear in within commands such - as ALTER FUNCTION. This form omits default values. - - - - - - - pg_get_function_result - - pg_get_function_result ( func oid ) - text - - - Reconstructs the RETURNS clause of a function, in - the form it would need to appear in within CREATE - FUNCTION. Returns NULL for a procedure. - - - - - - - pg_get_indexdef - - pg_get_indexdef ( index oid , column integer, pretty boolean ) - text - - - Reconstructs the creating command for an index. - (This is a decompiled reconstruction, not the original text - of the command.) If column is supplied and is - not zero, only the definition of that column is reconstructed. - - - - - - - pg_get_keywords - - pg_get_keywords () - setof record - ( word text, - catcode "char", - barelabel boolean, - catdesc text, - baredesc text ) - - - Returns a set of records describing the SQL keywords recognized by the - server. The word column contains the - keyword. The catcode column contains a - category code: U for an unreserved - keyword, C for a keyword that can be a column - name, T for a keyword that can be a type or - function name, or R for a fully reserved keyword. - The barelabel column - contains true if the keyword can be used as - a bare column label in SELECT lists, - or false if it can only be used - after AS. - The catdesc column contains a - possibly-localized string describing the keyword's category. - The baredesc column contains a - possibly-localized string describing the keyword's column label status. - - - - - - - pg_get_partkeydef - - pg_get_partkeydef ( table oid ) - text - - - Reconstructs the definition of a partitioned table's partition - key, in the form it would have in the PARTITION - BY clause of CREATE TABLE. - (This is a decompiled reconstruction, not the original text - of the command.) - - - - - - - pg_get_ruledef - - pg_get_ruledef ( rule oid , pretty boolean ) - text - - - Reconstructs the creating command for a rule. - (This is a decompiled reconstruction, not the original text - of the command.) - - - - - - - pg_get_serial_sequence - - pg_get_serial_sequence ( table text, column text ) - text - - - Returns the name of the sequence associated with a column, - or NULL if no sequence is associated with the column. - If the column is an identity column, the associated sequence is the - sequence internally created for that column. - For columns created using one of the serial types - (serial, smallserial, bigserial), - it is the sequence created for that serial column definition. - In the latter case, the association can be modified or removed - with ALTER SEQUENCE OWNED BY. - (This function probably should have been - called pg_get_owned_sequence; its current name - reflects the fact that it has historically been used with serial-type - columns.) The first parameter is a table name with optional - schema, and the second parameter is a column name. Because the first - parameter potentially contains both schema and table names, it is - parsed per usual SQL rules, meaning it is lower-cased by default. - The second parameter, being just a column name, is treated literally - and so has its case preserved. The result is suitably formatted - for passing to the sequence functions (see - ). - - - A typical use is in reading the current value of the sequence for an - identity or serial column, for example: - -SELECT currval(pg_get_serial_sequence('sometable', 'id')); - - - - - - - - pg_get_statisticsobjdef - - pg_get_statisticsobjdef ( statobj oid ) - text - - - Reconstructs the creating command for an extended statistics object. - (This is a decompiled reconstruction, not the original text - of the command.) - - - - - - - pg_get_triggerdef - -pg_get_triggerdef ( trigger oid , pretty boolean ) - text - - - Reconstructs the creating command for a trigger. - (This is a decompiled reconstruction, not the original text - of the command.) - - - - - - - pg_get_userbyid - - pg_get_userbyid ( role oid ) - name - - - Returns a role's name given its OID. - - - - - - - pg_get_viewdef - - pg_get_viewdef ( view oid , pretty boolean ) - text - - - Reconstructs the underlying SELECT command for a - view or materialized view. (This is a decompiled reconstruction, not - the original text of the command.) - - - - - - pg_get_viewdef ( view oid, wrap_column integer ) - text - - - Reconstructs the underlying SELECT command for a - view or materialized view. (This is a decompiled reconstruction, not - the original text of the command.) In this form of the function, - pretty-printing is always enabled, and long lines are wrapped to try - to keep them shorter than the specified number of columns. - - - - - - pg_get_viewdef ( view text , pretty boolean ) - text - - - Reconstructs the underlying SELECT command for a - view or materialized view, working from a textual name for the view - rather than its OID. (This is deprecated; use the OID variant - instead.) - - - - - - - pg_index_column_has_property - - pg_index_column_has_property ( index regclass, column integer, property text ) - boolean - - - Tests whether an index column has the named property. - Common index column properties are listed in - . - (Note that extension access methods can define additional property - names for their indexes.) - NULL is returned if the property name is not known - or does not apply to the particular object, or if the OID or column - number does not identify a valid object. - - - - - - - pg_index_has_property - - pg_index_has_property ( index regclass, property text ) - boolean - - - Tests whether an index has the named property. - Common index properties are listed in - . - (Note that extension access methods can define additional property - names for their indexes.) - NULL is returned if the property name is not known - or does not apply to the particular object, or if the OID does not - identify a valid object. - - - - - - - pg_indexam_has_property - - pg_indexam_has_property ( am oid, property text ) - boolean - - - Tests whether an index access method has the named property. - Access method properties are listed in - . - NULL is returned if the property name is not known - or does not apply to the particular object, or if the OID does not - identify a valid object. - - - - - - - pg_options_to_table - - pg_options_to_table ( options_array text[] ) - setof record - ( option_name text, - option_value text ) - - - Returns the set of storage options represented by a value from - pg_class.reloptions or - pg_attribute.attoptions. - - - - - - - pg_settings_get_flags - - pg_settings_get_flags ( guc text ) - text[] - - - Returns an array of the flags associated with the given GUC, or - NULL if it does not exist. The result is - an empty array if the GUC exists but there are no flags to show. - Only the most useful flags listed in - are exposed. - - - - - - - pg_tablespace_databases - - pg_tablespace_databases ( tablespace oid ) - setof oid - - - Returns the set of OIDs of databases that have objects stored in the - specified tablespace. If this function returns any rows, the - tablespace is not empty and cannot be dropped. To identify the specific - objects populating the tablespace, you will need to connect to the - database(s) identified by pg_tablespace_databases - and query their pg_class catalogs. - - - - - - - pg_tablespace_location - - pg_tablespace_location ( tablespace oid ) - text - - - Returns the file system path that this tablespace is located in. - - - - - - - pg_typeof - - pg_typeof ( "any" ) - regtype - - - Returns the OID of the data type of the value that is passed to it. - This can be helpful for troubleshooting or dynamically constructing - SQL queries. The function is declared as - returning regtype, which is an OID alias type (see - ); this means that it is the same as an - OID for comparison purposes but displays as a type name. - - - pg_typeof(33) - integer - - - - - - - COLLATION FOR - - COLLATION FOR ( "any" ) - text - - - Returns the name of the collation of the value that is passed to it. - The value is quoted and schema-qualified if necessary. If no - collation was derived for the argument expression, - then NULL is returned. If the argument is not of a - collatable data type, then an error is raised. - - - collation for ('foo'::text) - "default" - - - collation for ('foo' COLLATE "de_DE") - "de_DE" - - - - - - - to_regclass - - to_regclass ( text ) - regclass - - - Translates a textual relation name to its OID. A similar result is - obtained by casting the string to type regclass (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found. - - - - - - - to_regdatabase - - to_regdatabase ( text ) - regdatabase - - - Translates a textual database name to its OID. A similar result is - obtained by casting the string to type regdatabase (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found. - - - - - - - to_regcollation - - to_regcollation ( text ) - regcollation - - - Translates a textual collation name to its OID. A similar result is - obtained by casting the string to type regcollation (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found. - - - - - - - to_regnamespace - - to_regnamespace ( text ) - regnamespace - - - Translates a textual schema name to its OID. A similar result is - obtained by casting the string to type regnamespace (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found. - - - - - - - to_regoper - - to_regoper ( text ) - regoper - - - Translates a textual operator name to its OID. A similar result is - obtained by casting the string to type regoper (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found or is ambiguous. - - - - - - - to_regoperator - - to_regoperator ( text ) - regoperator - - - Translates a textual operator name (with parameter types) to its OID. A similar result is - obtained by casting the string to type regoperator (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found. - - - - - - - to_regproc - - to_regproc ( text ) - regproc - - - Translates a textual function or procedure name to its OID. A similar result is - obtained by casting the string to type regproc (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found or is ambiguous. - - - - - - - to_regprocedure - - to_regprocedure ( text ) - regprocedure - - - Translates a textual function or procedure name (with argument types) to its OID. A similar result is - obtained by casting the string to type regprocedure (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found. - - - - - - - to_regrole - - to_regrole ( text ) - regrole - - - Translates a textual role name to its OID. A similar result is - obtained by casting the string to type regrole (see - ); however, this function will return - NULL rather than throwing an error if the name is - not found. - - - - - - - to_regtype - - to_regtype ( text ) - regtype - - - Parses a string of text, extracts a potential type name from it, - and translates that name into a type OID. A syntax error in the - string will result in an error; but if the string is a - syntactically valid type name that happens not to be found in the - catalogs, the result is NULL. A similar result - is obtained by casting the string to type regtype - (see ), except that that will throw - error for name not found. - - - - - - - to_regtypemod - - to_regtypemod ( text ) - integer - - - Parses a string of text, extracts a potential type name from it, - and translates its type modifier, if any. A syntax error in the - string will result in an error; but if the string is a - syntactically valid type name that happens not to be found in the - catalogs, the result is NULL. The result is - -1 if no type modifier is present. - - - to_regtypemod can be combined with - to produce appropriate inputs for - , allowing a string representing a - type name to be canonicalized. - - - format_type(to_regtype('varchar(32)'), to_regtypemod('varchar(32)')) - character varying(32) - - - - -

- - - Most of the functions that reconstruct (decompile) database objects - have an optional pretty flag, which - if true causes the result to - be pretty-printed. Pretty-printing suppresses unnecessary - parentheses and adds whitespace for legibility. - The pretty-printed format is more readable, but the default format - is more likely to be interpreted the same way by future versions of - PostgreSQL; so avoid using pretty-printed output - for dump purposes. Passing false for - the pretty parameter yields the same result as - omitting the parameter. - - - - Index Column Properties - - - NameDescription - - - - asc - Does the column sort in ascending order on a forward scan? - - - - desc - Does the column sort in descending order on a forward scan? - - - - nulls_first - Does the column sort with nulls first on a forward scan? - - - - nulls_last - Does the column sort with nulls last on a forward scan? - - - - orderable - Does the column possess any defined sort ordering? - - - - distance_orderable - Can the column be scanned in order by a distance - operator, for example ORDER BY col <-> constant ? - - - - returnable - Can the column value be returned by an index-only scan? - - - - search_array - Does the column natively support col = ANY(array) - searches? - - - - search_nulls - Does the column support IS NULL and - IS NOT NULL searches? - - - - -

- - - Index Properties - - - NameDescription - - - - clusterable - Can the index be used in a CLUSTER command? - - - - index_scan - Does the index support plain (non-bitmap) scans? - - - - bitmap_scan - Does the index support bitmap scans? - - - - backward_scan - Can the scan direction be changed in mid-scan (to - support FETCH BACKWARD on a cursor without - needing materialization)? - - - - -

- - - Index Access Method Properties - - - NameDescription - - - - can_order - Does the access method support ASC, - DESC and related keywords in - CREATE INDEX? - - - - can_unique - Does the access method support unique indexes? - - - - can_multi_col - Does the access method support indexes with multiple columns? - - - - can_exclude - Does the access method support exclusion constraints? - - - - can_include - Does the access method support the INCLUDE - clause of CREATE INDEX? - - - - -

- - - GUC Flags - - - FlagDescription - - - - EXPLAIN - Parameters with this flag are included in - EXPLAIN (SETTINGS) commands. - - - - NO_SHOW_ALL - Parameters with this flag are excluded from - SHOW ALL commands. - - - - NO_RESET - Parameters with this flag do not support - RESET commands. - - - - NO_RESET_ALL - Parameters with this flag are excluded from - RESET ALL commands. - - - - NOT_IN_SAMPLE - Parameters with this flag are not included in - postgresql.conf by default. - - - - RUNTIME_COMPUTED - Parameters with this flag are runtime-computed ones. - - - - -

- - - - - Object Information and Addressing Functions - - - lists functions related to - database object identification and addressing. - - - - Object Information and Addressing Functions - - - - - Function - - - Description - - - - - - - - - pg_get_acl - - pg_get_acl ( classid oid, objid oid, objsubid integer ) - aclitem[] - - - Returns the ACL for a database object, specified - by catalog OID, object OID and sub-object ID. This function returns - NULL values for undefined objects. - - - - - - - pg_describe_object - - pg_describe_object ( classid oid, objid oid, objsubid integer ) - text - - - Returns a textual description of a database object identified by - catalog OID, object OID, and sub-object ID (such as a column number - within a table; the sub-object ID is zero when referring to a whole - object). This description is intended to be human-readable, and might - be translated, depending on server configuration. This is especially - useful to determine the identity of an object referenced in the - pg_depend catalog. This function returns - NULL values for undefined objects. - - - - - - - pg_identify_object - - pg_identify_object ( classid oid, objid oid, objsubid integer ) - record - ( type text, - schema text, - name text, - identity text ) - - - Returns a row containing enough information to uniquely identify the - database object specified by catalog OID, object OID and sub-object - ID. - This information is intended to be machine-readable, and is never - translated. - type identifies the type of database object; - schema is the schema name that the object - belongs in, or NULL for object types that do not - belong to schemas; - name is the name of the object, quoted if - necessary, if the name (along with schema name, if pertinent) is - sufficient to uniquely identify the object, - otherwise NULL; - identity is the complete object identity, with - the precise format depending on object type, and each name within the - format being schema-qualified and quoted as necessary. Undefined - objects are identified with NULL values. - - - - - - - pg_identify_object_as_address - - pg_identify_object_as_address ( classid oid, objid oid, objsubid integer ) - record - ( type text, - object_names text[], - object_args text[] ) - - - Returns a row containing enough information to uniquely identify the - database object specified by catalog OID, object OID and sub-object - ID. - The returned information is independent of the current server, that - is, it could be used to identify an identically named object in - another server. - type identifies the type of database object; - object_names and - object_args - are text arrays that together form a reference to the object. - These three values can be passed - to pg_get_object_address to obtain the internal - address of the object. - - - - - - - pg_get_object_address - - pg_get_object_address ( type text, object_names text[], object_args text[] ) - record - ( classid oid, - objid oid, - objsubid integer ) - - - Returns a row containing enough information to uniquely identify the - database object specified by a type code and object name and argument - arrays. - The returned values are the ones that would be used in system catalogs - such as pg_depend; they can be passed to - other system functions such as pg_describe_object - or pg_identify_object. - classid is the OID of the system catalog - containing the object; - objid is the OID of the object itself, and - objsubid is the sub-object ID, or zero if none. - This function is the inverse - of pg_identify_object_as_address. - Undefined objects are identified with NULL values. - - - - -

- - - pg_get_acl is useful for retrieving and inspecting - the privileges associated with database objects without looking at - specific catalogs. For example, to retrieve all the granted privileges - on objects in the current database: - -postgres=# SELECT - (pg_identify_object(s.classid,s.objid,s.objsubid)).*, - pg_catalog.pg_get_acl(s.classid,s.objid,s.objsubid) AS acl -FROM pg_catalog.pg_shdepend AS s -JOIN pg_catalog.pg_database AS d - ON d.datname = current_database() AND - d.oid = s.dbid -JOIN pg_catalog.pg_authid AS a - ON a.oid = s.refobjid AND - s.refclassid = 'pg_authid'::regclass -WHERE s.deptype = 'a'; --[ RECORD 1 ]----------------------------------------- -type | table -schema | public -name | testtab -identity | public.testtab -acl | {postgres=arwdDxtm/postgres,foo=r/postgres} - - - - - - - Comment Information Functions - - - comment - about database objects - - - - The functions shown in - extract comments previously stored with the - command. A null value is returned if no - comment could be found for the specified parameters. - - - - Comment Information Functions - - - - - Function - - - Description - - - - - - - - - col_description - - col_description ( table oid, column integer ) - text - - - Returns the comment for a table column, which is specified by the OID - of its table and its column number. - (obj_description cannot be used for table - columns, since columns do not have OIDs of their own.) - - - - - - - obj_description - - obj_description ( object oid, catalog name ) - text - - - Returns the comment for a database object specified by its OID and the - name of the containing system catalog. For - example, obj_description(123456, 'pg_class') would - retrieve the comment for the table with OID 123456. - - - - - - obj_description ( object oid ) - text - - - Returns the comment for a database object specified by its OID alone. - This is deprecated since there is no guarantee - that OIDs are unique across different system catalogs; therefore, the - wrong comment might be returned. - - - - - - - shobj_description - - shobj_description ( object oid, catalog name ) - text - - - Returns the comment for a shared database object specified by its OID - and the name of the containing system catalog. This is just - like obj_description except that it is used for - retrieving comments on shared objects (that is, databases, roles, and - tablespaces). Some system catalogs are global to all databases within - each cluster, and the descriptions for objects in them are stored - globally as well. - - - - -

- - - - - Data Validity Checking Functions - - - The functions shown in - can be helpful for checking validity of proposed input data. - - - - Data Validity Checking Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - pg_input_is_valid - - pg_input_is_valid ( - string text, - type text - ) - boolean - - - Tests whether the given string is valid - input for the specified data type, returning true or false. - - - This function will only work as desired if the data type's input - function has been updated to report invalid input as - a soft error. Otherwise, invalid input will abort - the transaction, just as if the string had been cast to the type - directly. - - - pg_input_is_valid('42', 'integer') - t - - - pg_input_is_valid('42000000000', 'integer') - f - - - pg_input_is_valid('1234.567', 'numeric(7,4)') - f - - - - - - pg_input_error_info - - pg_input_error_info ( - string text, - type text - ) - record - ( message text, - detail text, - hint text, - sql_error_code text ) - - - Tests whether the given string is valid - input for the specified data type; if not, return the details of - the error that would have been thrown. If the input is valid, the - results are NULL. The inputs are the same as - for pg_input_is_valid. - - - This function will only work as desired if the data type's input - function has been updated to report invalid input as - a soft error. Otherwise, invalid input will abort - the transaction, just as if the string had been cast to the type - directly. - - - SELECT * FROM pg_input_error_info('42000000000', 'integer') - - - message | detail | hint | sql_error_code -------------------------------------------------------+--------+------+---------------- - value "42000000000" is out of range for type integer | | | 22003 - - - - - -

- - - - - Transaction ID and Snapshot Information Functions - - - The functions shown in - provide server transaction information in an exportable form. The main - use of these functions is to determine which transactions were committed - between two snapshots. - - - - Transaction ID and Snapshot Information Functions - - - - - Function - - - Description - - - - - - - - - age - - age ( xid ) - integer - - - Returns the number of transactions between the supplied - transaction id and the current transaction counter. - - - - - - - mxid_age - - mxid_age ( xid ) - integer - - - Returns the number of multixacts IDs between the supplied - multixact ID and the current multixacts counter. - - - - - - - pg_current_xact_id - - pg_current_xact_id () - xid8 - - - Returns the current transaction's ID. It will assign a new one if the - current transaction does not have one already (because it has not - performed any database updates); see for details. If executed in a - subtransaction, this will return the top-level transaction ID; - see for details. - - - - - - - pg_current_xact_id_if_assigned - - pg_current_xact_id_if_assigned () - xid8 - - - Returns the current transaction's ID, or NULL if no - ID is assigned yet. (It's best to use this variant if the transaction - might otherwise be read-only, to avoid unnecessary consumption of an - XID.) - If executed in a subtransaction, this will return the top-level - transaction ID. - - - - - - - pg_xact_status - - pg_xact_status ( xid8 ) - text - - - Reports the commit status of a recent transaction. - The result is one of in progress, - committed, or aborted, - provided that the transaction is recent enough that the system retains - the commit status of that transaction. - If it is old enough that no references to the transaction survive in - the system and the commit status information has been discarded, the - result is NULL. - Applications might use this function, for example, to determine - whether their transaction committed or aborted after the application - and database server become disconnected while - a COMMIT is in progress. - Note that prepared transactions are reported as in - progress; applications must check pg_prepared_xacts - if they need to determine whether a transaction ID belongs to a - prepared transaction. - - - - - - - pg_current_snapshot - - pg_current_snapshot () - pg_snapshot - - - Returns a current snapshot, a data structure - showing which transaction IDs are now in-progress. - Only top-level transaction IDs are included in the snapshot; - subtransaction IDs are not shown; see - for details. - - - - - - - pg_snapshot_xip - - pg_snapshot_xip ( pg_snapshot ) - setof xid8 - - - Returns the set of in-progress transaction IDs contained in a snapshot. - - - - - - - pg_snapshot_xmax - - pg_snapshot_xmax ( pg_snapshot ) - xid8 - - - Returns the xmax of a snapshot. - - - - - - - pg_snapshot_xmin - - pg_snapshot_xmin ( pg_snapshot ) - xid8 - - - Returns the xmin of a snapshot. - - - - - - - pg_visible_in_snapshot - - pg_visible_in_snapshot ( xid8, pg_snapshot ) - boolean - - - Is the given transaction ID visible according - to this snapshot (that is, was it completed before the snapshot was - taken)? Note that this function will not give the correct answer for - a subtransaction ID (subxid); see for - details. - - - - - - - pg_get_multixact_members - - pg_get_multixact_members ( multixid xid ) - setof record - ( xid xid, - mode text ) - - - Returns the transaction ID and lock mode for each member of the - specified multixact ID. The lock modes forupd, - fornokeyupd, sh, and - keysh correspond to the row-level locks - FOR UPDATE, FOR NO KEY UPDATE, - FOR SHARE, and FOR KEY SHARE, - respectively, as described in . Two - additional modes are specific to multixacts: - nokeyupd, used by updates that do not modify key - columns, and upd, used by updates or deletes that - modify key columns. - - - - -

- - - The internal transaction ID type xid is 32 bits wide and - wraps around every 4 billion transactions. However, - the functions shown in , except - age, mxid_age, and - pg_get_multixact_members, use a - 64-bit type xid8 that does not wrap around during the life - of an installation and can be converted to xid by casting if - required; see for details. - The data type pg_snapshot stores information about - transaction ID visibility at a particular moment in time. Its components - are described in . - pg_snapshot's textual representation is - xmin:xmax:xip_list. - For example 10:20:10,14,15 means - xmin=10, xmax=20, xip_list=10, 14, 15. - - - - Snapshot Components - - - - Name - Description - - - - - - xmin - - Lowest transaction ID that was still active. All transaction IDs - less than xmin are either committed and visible, - or rolled back and dead. - - - - - xmax - - One past the highest completed transaction ID. All transaction IDs - greater than or equal to xmax had not yet - completed as of the time of the snapshot, and thus are invisible. - - - - - xip_list - - Transactions in progress at the time of the snapshot. A transaction - ID that is xmin <= X < - xmax and not in this list was already completed at the time - of the snapshot, and thus is either visible or dead according to its - commit status. This list does not include the transaction IDs of - subtransactions (subxids). - - - - -

- - - In releases of PostgreSQL before 13 there was - no xid8 type, so variants of these functions were provided - that used bigint to represent a 64-bit XID, with a - correspondingly distinct snapshot data type txid_snapshot. - These older functions have txid in their names. They - are still supported for backward compatibility, but may be removed from a - future release. See . - - - - Deprecated Transaction ID and Snapshot Information Functions - - - - - Function - - - Description - - - - - - - - - - txid_current - - txid_current () - bigint - - - See pg_current_xact_id(). - - - - - - - txid_current_if_assigned - - txid_current_if_assigned () - bigint - - - See pg_current_xact_id_if_assigned(). - - - - - - - txid_current_snapshot - - txid_current_snapshot () - txid_snapshot - - - See pg_current_snapshot(). - - - - - - - txid_snapshot_xip - - txid_snapshot_xip ( txid_snapshot ) - setof bigint - - - See pg_snapshot_xip(). - - - - - - - txid_snapshot_xmax - - txid_snapshot_xmax ( txid_snapshot ) - bigint - - - See pg_snapshot_xmax(). - - - - - - - txid_snapshot_xmin - - txid_snapshot_xmin ( txid_snapshot ) - bigint - - - See pg_snapshot_xmin(). - - - - - - - txid_visible_in_snapshot - - txid_visible_in_snapshot ( bigint, txid_snapshot ) - boolean - - - See pg_visible_in_snapshot(). - - - - - - - txid_status - - txid_status ( bigint ) - text - - - See pg_xact_status(). - - - - -

- - - - - Committed Transaction Information Functions - - - The functions shown in - provide information about when past transactions were committed. - They only provide useful data when the - configuration option is - enabled, and only for transactions that were committed after it was - enabled. Commit timestamp information is routinely removed during - vacuum. - - - - Committed Transaction Information Functions - - - - - Function - - - Description - - - - - - - - - pg_xact_commit_timestamp - - pg_xact_commit_timestamp ( xid ) - timestamp with time zone - - - Returns the commit timestamp of a transaction. - - - - - - - pg_xact_commit_timestamp_origin - - pg_xact_commit_timestamp_origin ( xid ) - record - ( timestamp timestamp with time zone, - roident oid) - - - Returns the commit timestamp and replication origin of a transaction. - - - - - - - pg_last_committed_xact - - pg_last_committed_xact () - record - ( xid xid, - timestamp timestamp with time zone, - roident oid ) - - - Returns the transaction ID, commit timestamp and replication origin - of the latest committed transaction. - - - - -

- - - - - Control Data Functions - - - The functions shown in - print information initialized during initdb, such - as the catalog version. They also show information about write-ahead - logging and checkpoint processing. This information is cluster-wide, - not specific to any one database. These functions provide most of the same - information, from the same source, as the - application. - - - - Control Data Functions - - - - - Function - - - Description - - - - - - - - - pg_control_checkpoint - - pg_control_checkpoint () - record - - - Returns information about current checkpoint state, as shown in - . - - - - - - - pg_control_system - - pg_control_system () - record - - - Returns information about current control file state, as shown in - . - - - - - - - pg_control_init - - pg_control_init () - record - - - Returns information about cluster initialization state, as shown in - . - - - - - - - pg_control_recovery - - pg_control_recovery () - record - - - Returns information about recovery state, as shown in - . - - - - -

- - - <function>pg_control_checkpoint</function> Output Columns - - - - Column Name - Data Type - - - - - - - checkpoint_lsn - pg_lsn - - - - redo_lsn - pg_lsn - - - - redo_wal_file - text - - - - timeline_id - integer - - - - prev_timeline_id - integer - - - - full_page_writes - boolean - - - - next_xid - text - - - - next_oid - oid - - - - next_multixact_id - xid - - - - next_multi_offset - xid - - - - oldest_xid - xid - - - - oldest_xid_dbid - oid - - - - oldest_active_xid - xid - - - - oldest_multi_xid - xid - - - - oldest_multi_dbid - oid - - - - oldest_commit_ts_xid - xid - - - - newest_commit_ts_xid - xid - - - - checkpoint_time - timestamp with time zone - - - - -

- - - <function>pg_control_system</function> Output Columns - - - - Column Name - Data Type - - - - - - - pg_control_version - integer - - - - catalog_version_no - integer - - - - system_identifier - bigint - - - - pg_control_last_modified - timestamp with time zone - - - - -

- - - <function>pg_control_init</function> Output Columns - - - - Column Name - Data Type - - - - - - - max_data_alignment - integer - - - - database_block_size - integer - - - - blocks_per_segment - integer - - - - wal_block_size - integer - - - - bytes_per_wal_segment - integer - - - - max_identifier_length - integer - - - - max_index_columns - integer - - - - max_toast_chunk_size - integer - - - - large_object_chunk_size - integer - - - - float8_pass_by_value - boolean - - - - data_page_checksum_version - integer - - - - default_char_signedness - boolean - - - - -

- - - <function>pg_control_recovery</function> Output Columns - - - - Column Name - Data Type - - - - - - - min_recovery_end_lsn - pg_lsn - - - - min_recovery_end_timeline - integer - - - - backup_start_lsn - pg_lsn - - - - backup_end_lsn - pg_lsn - - - - end_of_backup_record_required - boolean - - - - -

- - - - - Version Information Functions - - - The functions shown in - print version information. - - - - Version Information Functions - - - - - Function - - - Description - - - - - - - - - version - - version () - text - - - Returns a string describing the PostgreSQL - server's version. You can also get this information from - , or for a machine-readable - version use . Software - developers should use server_version_num (available - since 8.2) or instead of - parsing the text version. - - - - - - - unicode_version - - unicode_version () - text - - - Returns a string representing the version of Unicode used by - PostgreSQL. - - - - - - icu_unicode_version - - icu_unicode_version () - text - - - Returns a string representing the version of Unicode used by ICU, if - the server was built with ICU support; otherwise returns - NULL - - - -

- - - - - WAL Summarization Information Functions - - - The functions shown in - print information about the status of WAL summarization. - See . - - - - WAL Summarization Information Functions - - - - - Function - - - Description - - - - - - - - - pg_available_wal_summaries - - pg_available_wal_summaries () - setof record - ( tli bigint, - start_lsn pg_lsn, - end_lsn pg_lsn ) - - - Returns information about the WAL summary files present in the - data directory, under pg_wal/summaries. - One row will be returned per WAL summary file. Each file summarizes - WAL on the indicated TLI within the indicated LSN range. This function - might be useful to determine whether enough WAL summaries are present - on the server to take an incremental backup based on some prior - backup whose start LSN is known. - - - - - - - pg_wal_summary_contents - - pg_wal_summary_contents ( tli bigint, start_lsn pg_lsn, end_lsn pg_lsn ) - setof record - ( relfilenode oid, - reltablespace oid, - reldatabase oid, - relforknumber smallint, - relblocknumber bigint, - is_limit_block boolean ) - - - Returns one information about the contents of a single WAL summary file - identified by TLI and starting and ending LSNs. Each row with - is_limit_block false indicates that the block - identified by the remaining output columns was modified by at least - one WAL record within the range of records summarized by this file. - Each row with is_limit_block true indicates either - that (a) the relation fork was truncated to the length given by - relblocknumber within the relevant range of WAL - records or (b) that the relation fork was created or dropped within - the relevant range of WAL records; in such cases, - relblocknumber will be zero. - - - - - - - pg_get_wal_summarizer_state - - pg_get_wal_summarizer_state () - record - ( summarized_tli bigint, - summarized_lsn pg_lsn, - pending_lsn pg_lsn, - summarizer_pid int ) - - - Returns information about the progress of the WAL summarizer. If the - WAL summarizer has never run since the instance was started, then - summarized_tli and summarized_lsn - will be 0 and 0/00000000 respectively; - otherwise, they will be the TLI and ending LSN of the last WAL summary - file written to disk. If the WAL summarizer is currently running, - pending_lsn will be the ending LSN of the last - record that it has consumed, which must always be greater than or - equal to summarized_lsn; if the WAL summarizer is - not running, it will be equal to summarized_lsn. - summarizer_pid is the PID of the WAL summarizer - process, if it is running, and otherwise NULL. - - - As a special exception, the WAL summarizer will refuse to generate - WAL summary files if run on WAL generated under - wal_level=minimal, since such summaries would be - unsafe to use as the basis for an incremental backup. In this case, - the fields above will continue to advance as if summaries were being - generated, but nothing will be written to disk. Once the summarizer - reaches WAL generated while wal_level was set - to replica or higher, it will resume writing - summaries to disk. - - - - -

- - - - - - - System Administration Functions - - - The functions described in this section are used to control and - monitor a PostgreSQL installation. - - - - Configuration Settings Functions - - - SET - - - - SHOW - - - - configuration - of the server - functions - - - - shows the functions - available to query and alter run-time configuration parameters. - - - - Configuration Settings Functions - - - - - Function - - - Description - - - Example(s) - - - - - - - - - current_setting - - current_setting ( setting_name text , missing_ok boolean ) - text - - - Returns the current value of the - setting setting_name. If there is no such - setting, current_setting throws an error - unless missing_ok is supplied and - is true (in which case NULL is returned). - This function corresponds to - the SQL command . - - - current_setting('datestyle') - ISO, MDY - - - - - - - set_config - - set_config ( - setting_name text, - new_value text, - is_local boolean ) - text - - - Sets the parameter setting_name - to new_value, and returns that value. - If is_local is true, the new - value will only apply during the current transaction. If you want the - new value to apply for the rest of the current session, - use false instead. This function corresponds to - the SQL command . - - - set_config accepts the NULL value for - new_value, but as settings cannot be null, it - is interpreted as a request to reset the setting to its default value. - - - set_config('log_statement_stats', 'off', false) - off - - - - -

- - - - - Server Signaling Functions - - - signal - backend processes - - - - The functions shown in send control signals to - other server processes. Use of these functions is restricted to - superusers by default but access may be granted to others using - GRANT, with noted exceptions. - - - - Each of these functions returns true if - the signal was successfully sent and false - if sending the signal failed. - - - - Server Signaling Functions - - - - - Function - - - Description - - - - - - - - - pg_cancel_backend - - pg_cancel_backend ( pid integer ) - boolean - - - Cancels the current query of the session whose backend process has the - specified process ID. This is also allowed if the - calling role is a member of the role whose backend is being canceled or - the calling role has privileges of pg_signal_backend, - however only superusers can cancel superuser backends. - As an exception, roles with privileges of - pg_signal_autovacuum_worker are permitted to - cancel autovacuum worker processes, which are otherwise considered - superuser backends. - - - - - - - pg_log_backend_memory_contexts - - pg_log_backend_memory_contexts ( pid integer ) - boolean - - - Requests to log the memory contexts of the backend with the - specified process ID. This function can send the request to - backends and auxiliary processes except logger. These memory contexts - will be logged at - LOG message level. They will appear in - the server log based on the log configuration set - (see for more information), - but will not be sent to the client regardless of - . - - - - - - - pg_reload_conf - - pg_reload_conf () - boolean - - - Causes all processes of the PostgreSQL - server to reload their configuration files. (This is initiated by - sending a SIGHUP signal to the postmaster - process, which in turn sends SIGHUP to each - of its children.) You can use the - pg_file_settings, - pg_hba_file_rules and - pg_ident_file_mappings views - to check the configuration files for possible errors, before reloading. - - - - - - - pg_rotate_logfile - - pg_rotate_logfile () - boolean - - - Signals the log-file manager to switch to a new output file - immediately. This works only when the built-in log collector is - running, since otherwise there is no log-file manager subprocess. - - - - - - - pg_terminate_backend - - pg_terminate_backend ( pid integer, timeout bigint DEFAULT 0 ) - boolean - - - Terminates the session whose backend process has the - specified process ID. This is also allowed if the calling role - is a member of the role whose backend is being terminated or the - calling role has privileges of pg_signal_backend, - however only superusers can terminate superuser backends. - As an exception, roles with privileges of - pg_signal_autovacuum_worker are permitted to - terminate autovacuum worker processes, which are otherwise considered - superuser backends. - - - If timeout is not specified or zero, this - function returns true whether the process actually - terminates or not, indicating only that the sending of the signal was - successful. If the timeout is specified (in - milliseconds) and greater than zero, the function waits until the - process is actually terminated or until the given time has passed. If - the process is terminated, the function - returns true. On timeout, a warning is emitted and - false is returned. - - - - -

- - - pg_cancel_backend and pg_terminate_backend - send signals (SIGINT or SIGTERM - respectively) to backend processes identified by process ID. - The process ID of an active backend can be found from - the pid column of the - pg_stat_activity view, or by listing the - postgres processes on the server (using - ps on Unix or the Task - Manager on Windows). - The role of an active backend can be found from the - usename column of the - pg_stat_activity view. - - - - pg_log_backend_memory_contexts can be used - to log the memory contexts of a backend process. For example: - -postgres=# SELECT pg_log_backend_memory_contexts(pg_backend_pid()); - pg_log_backend_memory_contexts --------------------------------- - t -(1 row) - -One message for each memory context will be logged. For example: - -LOG: logging memory contexts of PID 10377 -STATEMENT: SELECT pg_log_backend_memory_contexts(pg_backend_pid()); -LOG: level: 1; TopMemoryContext: 80800 total in 6 blocks; 14432 free (5 chunks); 66368 used -LOG: level: 2; pgstat TabStatusArray lookup hash table: 8192 total in 1 blocks; 1408 free (0 chunks); 6784 used -LOG: level: 2; TopTransactionContext: 8192 total in 1 blocks; 7720 free (1 chunks); 472 used -LOG: level: 2; RowDescriptionContext: 8192 total in 1 blocks; 6880 free (0 chunks); 1312 used -LOG: level: 2; MessageContext: 16384 total in 2 blocks; 5152 free (0 chunks); 11232 used -LOG: level: 2; Operator class cache: 8192 total in 1 blocks; 512 free (0 chunks); 7680 used -LOG: level: 2; smgr relation table: 16384 total in 2 blocks; 4544 free (3 chunks); 11840 used -LOG: level: 2; TransactionAbortContext: 32768 total in 1 blocks; 32504 free (0 chunks); 264 used -... -LOG: level: 2; ErrorContext: 8192 total in 1 blocks; 7928 free (3 chunks); 264 used -LOG: Grand total: 1651920 bytes in 201 blocks; 622360 free (88 chunks); 1029560 used - - If there are more than 100 child contexts under the same parent, the first - 100 child contexts are logged, along with a summary of the remaining contexts. - Note that frequent calls to this function could incur significant overhead, - because it may generate a large number of log messages. - - - - - - Backup Control Functions - - - backup - - - - The functions shown in assist in making on-line backups. - These functions cannot be executed during recovery (except - pg_backup_start, - pg_backup_stop, - and pg_wal_lsn_diff). - - - - For details about proper usage of these functions, see - . - - - - Backup Control Functions - - - - - Function - - - Description - - - - - - - - - pg_create_restore_point - - pg_create_restore_point ( name text ) - pg_lsn - - - Creates a named marker record in the write-ahead log that can later be - used as a recovery target, and returns the corresponding write-ahead - log location. The given name can then be used with - to specify the point up to - which recovery will proceed. Avoid creating multiple restore points - with the same name, since recovery will stop at the first one whose - name matches the recovery target. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - - - pg_current_wal_flush_lsn - - pg_current_wal_flush_lsn () - pg_lsn - - - Returns the current write-ahead log flush location (see notes below). - - - - - - - pg_current_wal_insert_lsn - - pg_current_wal_insert_lsn () - pg_lsn - - - Returns the current write-ahead log insert location (see notes below). - - - - - - - pg_current_wal_lsn - - pg_current_wal_lsn () - pg_lsn - - - Returns the current write-ahead log write location (see notes below). - - - - - - - pg_backup_start - - pg_backup_start ( - label text - , fast boolean - ) - pg_lsn - - - Prepares the server to begin an on-line backup. The only required - parameter is an arbitrary user-defined label for the backup. - (Typically this would be the name under which the backup dump file - will be stored.) - If the optional second parameter is given as true, - it specifies executing pg_backup_start as quickly - as possible. This forces a fast checkpoint which will cause a - spike in I/O operations, slowing any concurrently executing queries. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - - - pg_backup_stop - - pg_backup_stop ( - wait_for_archive boolean - ) - record - ( lsn pg_lsn, - labelfile text, - spcmapfile text ) - - - Finishes performing an on-line backup. The desired contents of the - backup label file and the tablespace map file are returned as part of - the result of the function and must be written to files in the - backup area. These files must not be written to the live data directory - (doing so will cause PostgreSQL to fail to restart in the event of a - crash). - - - There is an optional parameter of type boolean. - If false, the function will return immediately after the backup is - completed, without waiting for WAL to be archived. This behavior is - only useful with backup software that independently monitors WAL - archiving. Otherwise, WAL required to make the backup consistent might - be missing and make the backup useless. By default or when this - parameter is true, pg_backup_stop will wait for - WAL to be archived when archiving is enabled. (On a standby, this - means that it will wait only when archive_mode = - always. If write activity on the primary is low, - it may be useful to run pg_switch_wal on the - primary in order to trigger an immediate segment switch.) - - - When executed on a primary, this function also creates a backup - history file in the write-ahead log archive area. The history file - includes the label given to pg_backup_start, the - starting and ending write-ahead log locations for the backup, and the - starting and ending times of the backup. After recording the ending - location, the current write-ahead log insertion point is automatically - advanced to the next write-ahead log file, so that the ending - write-ahead log file can be archived immediately to complete the - backup. - - - The result of the function is a single record. - The lsn column holds the backup's ending - write-ahead log location (which again can be ignored). The second - column returns the contents of the backup label file, and the third - column returns the contents of the tablespace map file. These must be - stored as part of the backup and are required as part of the restore - process. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - - - pg_switch_wal - - pg_switch_wal () - pg_lsn - - - Forces the server to switch to a new write-ahead log file, which - allows the current file to be archived (assuming you are using - continuous archiving). The result is the ending write-ahead log - location plus 1 within the just-completed write-ahead log file. If - there has been no write-ahead log activity since the last write-ahead - log switch, pg_switch_wal does nothing and - returns the start location of the write-ahead log file currently in - use. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - - - pg_walfile_name - - pg_walfile_name ( lsn pg_lsn ) - text - - - Converts a write-ahead log location to the name of the WAL file - holding that location. - - - - - - - pg_walfile_name_offset - - pg_walfile_name_offset ( lsn pg_lsn ) - record - ( file_name text, - file_offset integer ) - - - Converts a write-ahead log location to a WAL file name and byte offset - within that file. - - - - - - - pg_split_walfile_name - - pg_split_walfile_name ( file_name text ) - record - ( segment_number numeric, - timeline_id bigint ) - - - Extracts the sequence number and timeline ID from a WAL file - name. - - - - - - - pg_wal_lsn_diff - - pg_wal_lsn_diff ( lsn1 pg_lsn, lsn2 pg_lsn ) - numeric - - - Calculates the difference in bytes (lsn1 - lsn2) between two write-ahead log - locations. This can be used - with pg_stat_replication or some of the - functions shown in to - get the replication lag. - - - - -

- - - pg_current_wal_lsn displays the current write-ahead - log write location in the same format used by the above functions. - Similarly, pg_current_wal_insert_lsn displays the - current write-ahead log insertion location - and pg_current_wal_flush_lsn displays the current - write-ahead log flush location. The insertion location is - the logical end of the write-ahead log at any instant, - while the write location is the end of what has actually been written out - from the server's internal buffers, and the flush location is the last - location known to be written to durable storage. The write location is the - end of what can be examined from outside the server, and is usually what - you want if you are interested in archiving partially-complete write-ahead - log files. The insertion and flush locations are made available primarily - for server debugging purposes. These are all read-only operations and do - not require superuser permissions. - - - - You can use pg_walfile_name_offset to extract the - corresponding write-ahead log file name and byte offset from - a pg_lsn value. For example: - -postgres=# SELECT * FROM pg_walfile_name_offset((pg_backup_stop()).lsn); - file_name | file_offset ---------------------------+------------- - 00000001000000000000000D | 4039624 -(1 row) - - Similarly, pg_walfile_name extracts just the write-ahead log file name. - - - - pg_split_walfile_name is useful to compute a - LSN from a file offset and WAL file name, for example: - -postgres=# \set file_name '000000010000000100C000AB' -postgres=# \set offset 256 -postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset AS lsn - FROM pg_split_walfile_name(:'file_name') pd, - pg_show_all_settings() ps - WHERE ps.name = 'wal_segment_size'; - lsn ---------------- - C001/AB000100 -(1 row) - - - - - - - Recovery Control Functions - - - The functions shown in provide information - about the current status of a standby server. - These functions may be executed both during recovery and in normal running. - - - - Recovery Information Functions - - - - - Function - - - Description - - - - - - - - - pg_is_in_recovery - - pg_is_in_recovery () - boolean - - - Returns true if recovery is still in progress. - - - - - - - pg_last_wal_receive_lsn - - pg_last_wal_receive_lsn () - pg_lsn - - - Returns the last write-ahead log location that has been received and - synced to disk by streaming replication. While streaming replication - is in progress this will increase monotonically. If recovery has - completed then this will remain static at the location of the last WAL - record received and synced to disk during recovery. If streaming - replication is disabled, or if it has not yet started, the function - returns NULL. - - - - - - - pg_last_wal_replay_lsn - - pg_last_wal_replay_lsn () - pg_lsn - - - Returns the last write-ahead log location that has been replayed - during recovery. If recovery is still in progress this will increase - monotonically. If recovery has completed then this will remain - static at the location of the last WAL record applied during recovery. - When the server has been started normally without recovery, the - function returns NULL. - - - - - - - pg_last_xact_replay_timestamp - - pg_last_xact_replay_timestamp () - timestamp with time zone - - - Returns the time stamp of the last transaction replayed during - recovery. This is the time at which the commit or abort WAL record - for that transaction was generated on the primary. If no transactions - have been replayed during recovery, the function - returns NULL. Otherwise, if recovery is still in - progress this will increase monotonically. If recovery has completed - then this will remain static at the time of the last transaction - applied during recovery. When the server has been started normally - without recovery, the function returns NULL. - - - - - - - pg_get_wal_resource_managers - - pg_get_wal_resource_managers () - setof record - ( rm_id integer, - rm_name text, - rm_builtin boolean ) - - - Returns the currently-loaded WAL resource managers in the system. The - column rm_builtin indicates whether it's a - built-in resource manager, or a custom resource manager loaded by an - extension. - - - - -

- - - The functions shown in control the progress of recovery. - These functions may be executed only during recovery. - - - - Recovery Control Functions - - - - - Function - - - Description - - - - - - - - - pg_is_wal_replay_paused - - pg_is_wal_replay_paused () - boolean - - - Returns true if recovery pause is requested. - - - - - - - pg_get_wal_replay_pause_state - - pg_get_wal_replay_pause_state () - text - - - Returns recovery pause state. The return values are - not paused if pause is not requested, - pause requested if pause is requested but recovery is - not yet paused, and paused if the recovery is - actually paused. - - - - - - - pg_promote - - pg_promote ( wait boolean DEFAULT true, wait_seconds integer DEFAULT 60 ) - boolean - - - Promotes a standby server to primary status. - With wait set to true (the - default), the function waits until promotion is completed - or wait_seconds seconds have passed, and - returns true if promotion is successful - and false otherwise. - If wait is set to false, the - function returns true immediately after sending a - SIGUSR1 signal to the postmaster to trigger - promotion. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - - - pg_wal_replay_pause - - pg_wal_replay_pause () - void - - - Request to pause recovery. A request doesn't mean that recovery stops - right away. If you want a guarantee that recovery is actually paused, - you need to check for the recovery pause state returned by - pg_get_wal_replay_pause_state(). Note that - pg_is_wal_replay_paused() returns whether a request - is made. While recovery is paused, no further database changes are applied. - If hot standby is active, all new queries will see the same consistent - snapshot of the database, and no further query conflicts will be generated - until recovery is resumed. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - - - pg_wal_replay_resume - - pg_wal_replay_resume () - void - - - Restarts recovery if it was paused. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - -

- - - pg_wal_replay_pause and - pg_wal_replay_resume cannot be executed while - a promotion is ongoing. If a promotion is triggered while recovery - is paused, the paused state ends and promotion continues. - - - - If streaming replication is disabled, the paused state may continue - indefinitely without a problem. If streaming replication is in - progress then WAL records will continue to be received, which will - eventually fill available disk space, depending upon the duration of - the pause, the rate of WAL generation and available disk space. - - - - - - Snapshot Synchronization Functions - - - PostgreSQL allows database sessions to synchronize their - snapshots. A snapshot determines which data is visible to the - transaction that is using the snapshot. Synchronized snapshots are - necessary when two or more sessions need to see identical content in the - database. If two sessions just start their transactions independently, - there is always a possibility that some third transaction commits - between the executions of the two START TRANSACTION commands, - so that one session sees the effects of that transaction and the other - does not. - - - - To solve this problem, PostgreSQL allows a transaction to - export the snapshot it is using. As long as the exporting - transaction remains open, other transactions can import its - snapshot, and thereby be guaranteed that they see exactly the same view - of the database that the first transaction sees. But note that any - database changes made by any one of these transactions remain invisible - to the other transactions, as is usual for changes made by uncommitted - transactions. So the transactions are synchronized with respect to - pre-existing data, but act normally for changes they make themselves. - - - - Snapshots are exported with the pg_export_snapshot function, - shown in , and - imported with the command. - - - - Snapshot Synchronization Functions - - - - - Function - - - Description - - - - - - - - - pg_export_snapshot - - pg_export_snapshot () - text - - - Saves the transaction's current snapshot and returns - a text string identifying the snapshot. This string must - be passed (outside the database) to clients that want to import the - snapshot. The snapshot is available for import only until the end of - the transaction that exported it. - - - A transaction can export more than one snapshot, if needed. Note that - doing so is only useful in READ COMMITTED - transactions, since in REPEATABLE READ and higher - isolation levels, transactions use the same snapshot throughout their - lifetime. Once a transaction has exported any snapshots, it cannot be - prepared with . - - - - - - pg_log_standby_snapshot - - pg_log_standby_snapshot () - pg_lsn - - - Take a snapshot of running transactions and write it to WAL, without - having to wait for bgwriter or checkpointer to log one. This is useful - for logical decoding on standby, as logical slot creation has to wait - until such a record is replayed on the standby. - - - - -

- - - - - Replication Management Functions - - - The functions shown - in are for - controlling and interacting with replication features. - See , - , and - - for information about the underlying features. - Use of functions for replication origin is only allowed to the - superuser by default, but may be allowed to other users by using the - GRANT command. - Use of functions for replication slots is restricted to superusers - and users having REPLICATION privilege. - - - - Many of these functions have equivalent commands in the replication - protocol; see . - - - - The functions described in - , - , and - - are also relevant for replication. - - - - Replication Management Functions - - - - - Function - - - Description - - - - - - - - - pg_create_physical_replication_slot - - pg_create_physical_replication_slot ( slot_name name , immediately_reserve boolean, temporary boolean ) - record - ( slot_name name, - lsn pg_lsn ) - - - Creates a new physical replication slot named - slot_name. The name cannot be - pg_conflict_detection as it is reserved for the - conflict detection slot. The optional second parameter, - when true, specifies that the LSN for this - replication slot be reserved immediately; otherwise - the LSN is reserved on first connection from a streaming - replication client. Streaming changes from a physical slot is only - possible with the streaming-replication protocol — - see . The optional third - parameter, temporary, when set to true, specifies that - the slot should not be permanently stored to disk and is only meant - for use by the current session. Temporary slots are also - released upon any error. This function corresponds - to the replication protocol command CREATE_REPLICATION_SLOT - ... PHYSICAL. - - - - - - - pg_drop_replication_slot - - pg_drop_replication_slot ( slot_name name ) - void - - - Drops the physical or logical replication slot - named slot_name. Same as replication protocol - command DROP_REPLICATION_SLOT. - - - - - - - pg_create_logical_replication_slot - - pg_create_logical_replication_slot ( slot_name name, plugin name , temporary boolean, twophase boolean, failover boolean ) - record - ( slot_name name, - lsn pg_lsn ) - - - Creates a new logical (decoding) replication slot named - slot_name using the output plugin - plugin. The name cannot be - pg_conflict_detection as it is reserved for - the conflict detection slot. The optional third - parameter, temporary, when set to true, specifies that - the slot should not be permanently stored to disk and is only meant - for use by the current session. Temporary slots are also - released upon any error. The optional fourth parameter, - twophase, when set to true, specifies - that the decoding of prepared transactions is enabled for this - slot. The optional fifth parameter, - failover, when set to true, - specifies that this slot is enabled to be synced to the - standbys so that logical replication can be resumed after - failover. A call to this function has the same effect as - the replication protocol command - CREATE_REPLICATION_SLOT ... LOGICAL. - - - - - - - pg_copy_physical_replication_slot - - pg_copy_physical_replication_slot ( src_slot_name name, dst_slot_name name , temporary boolean ) - record - ( slot_name name, - lsn pg_lsn ) - - - Copies an existing physical replication slot named src_slot_name - to a physical replication slot named dst_slot_name. - The new slot name cannot be pg_conflict_detection, - as it is reserved for the conflict detection. - The copied physical slot starts to reserve WAL from the same LSN as the - source slot. - temporary is optional. If temporary - is omitted, the same value as the source slot is used. Copy of an - invalidated slot is not allowed. - - - - - - - pg_copy_logical_replication_slot - - pg_copy_logical_replication_slot ( src_slot_name name, dst_slot_name name , temporary boolean , plugin name ) - record - ( slot_name name, - lsn pg_lsn ) - - - Copies an existing logical replication slot - named src_slot_name to a logical replication - slot named dst_slot_name, optionally changing - the output plugin and persistence. The new slot name cannot be - pg_conflict_detection as it is reserved for - the conflict detection. The copied logical slot starts from the same - LSN as the source logical slot. Both - temporary and plugin are - optional; if they are omitted, the values of the source slot are used. - The failover option of the source logical slot - is not copied and is set to false by default. This - is to avoid the risk of being unable to continue logical replication - after failover to standby where the slot is being synchronized. Copy of - an invalidated slot is not allowed. - - - - - - - pg_logical_slot_get_changes - - pg_logical_slot_get_changes ( slot_name name, upto_lsn pg_lsn, upto_nchanges integer, VARIADIC options text[] ) - setof record - ( lsn pg_lsn, - xid xid, - data text ) - - - Returns changes in the slot slot_name, starting - from the point from which changes have been consumed last. If - upto_lsn - and upto_nchanges are NULL, - logical decoding will continue until end of WAL. If - upto_lsn is non-NULL, decoding will include only - those transactions which commit prior to the specified LSN. If - upto_nchanges is non-NULL, decoding will - stop when the number of rows produced by decoding exceeds - the specified value. Note, however, that the actual number of - rows returned may be larger, since this limit is only checked after - adding the rows produced when decoding each new transaction commit. - If the specified slot is a logical failover slot then the function will - not return until all physical slots specified in - synchronized_standby_slots - have confirmed WAL receipt. - - - - - - - pg_logical_slot_peek_changes - - pg_logical_slot_peek_changes ( slot_name name, upto_lsn pg_lsn, upto_nchanges integer, VARIADIC options text[] ) - setof record - ( lsn pg_lsn, - xid xid, - data text ) - - - Behaves just like - the pg_logical_slot_get_changes() function, - except that changes are not consumed; that is, they will be returned - again on future calls. - - - - - - - pg_logical_slot_get_binary_changes - - pg_logical_slot_get_binary_changes ( slot_name name, upto_lsn pg_lsn, upto_nchanges integer, VARIADIC options text[] ) - setof record - ( lsn pg_lsn, - xid xid, - data bytea ) - - - Behaves just like - the pg_logical_slot_get_changes() function, - except that changes are returned as bytea. - - - - - - - pg_logical_slot_peek_binary_changes - - pg_logical_slot_peek_binary_changes ( slot_name name, upto_lsn pg_lsn, upto_nchanges integer, VARIADIC options text[] ) - setof record - ( lsn pg_lsn, - xid xid, - data bytea ) - - - Behaves just like - the pg_logical_slot_peek_changes() function, - except that changes are returned as bytea. - - - - - - - pg_replication_slot_advance - - pg_replication_slot_advance ( slot_name name, upto_lsn pg_lsn ) - record - ( slot_name name, - end_lsn pg_lsn ) - - - Advances the current confirmed position of a replication slot named - slot_name. The slot will not be moved backwards, - and it will not be moved beyond the current insert location. Returns - the name of the slot and the actual position that it was advanced to. - The updated slot position information is written out at the next - checkpoint if any advancing is done. So in the event of a crash, the - slot may return to an earlier position. If the specified slot is a - logical failover slot then the function will not return until all - physical slots specified in - synchronized_standby_slots - have confirmed WAL receipt. - - - - - - - pg_replication_origin_create - - pg_replication_origin_create ( node_name text ) - oid - - - Creates a replication origin with the given external - name, and returns the internal ID assigned to it. - The name must be no longer than 512 bytes. - - - - - - - pg_replication_origin_drop - - pg_replication_origin_drop ( node_name text ) - void - - - Deletes a previously-created replication origin, including any - associated replay progress. - - - - - - - pg_replication_origin_oid - - pg_replication_origin_oid ( node_name text ) - oid - - - Looks up a replication origin by name and returns the internal ID. If - no such replication origin is found, NULL is - returned. - - - - - - - pg_replication_origin_session_setup - - pg_replication_origin_session_setup ( node_name text ) - void - - - Marks the current session as replaying from the given - origin, allowing replay progress to be tracked. - Can only be used if no origin is currently selected. - Use pg_replication_origin_session_reset to undo. - - - - - - - pg_replication_origin_session_reset - - pg_replication_origin_session_reset () - void - - - Cancels the effects - of pg_replication_origin_session_setup(). - - - - - - - pg_replication_origin_session_is_setup - - pg_replication_origin_session_is_setup () - boolean - - - Returns true if a replication origin has been selected in the - current session. - - - - - - - pg_replication_origin_session_progress - - pg_replication_origin_session_progress ( flush boolean ) - pg_lsn - - - Returns the replay location for the replication origin selected in - the current session. The parameter flush - determines whether the corresponding local transaction will be - guaranteed to have been flushed to disk or not. - - - - - - - pg_replication_origin_xact_setup - - pg_replication_origin_xact_setup ( origin_lsn pg_lsn, origin_timestamp timestamp with time zone ) - void - - - Marks the current transaction as replaying a transaction that has - committed at the given LSN and timestamp. Can - only be called when a replication origin has been selected - using pg_replication_origin_session_setup. - - - - - - - pg_replication_origin_xact_reset - - pg_replication_origin_xact_reset () - void - - - Cancels the effects of - pg_replication_origin_xact_setup(). - - - - - - - pg_replication_origin_advance - - pg_replication_origin_advance ( node_name text, lsn pg_lsn ) - void - - - Sets replication progress for the given node to the given - location. This is primarily useful for setting up the initial - location, or setting a new location after configuration changes and - similar. Be aware that careless use of this function can lead to - inconsistently replicated data. - - - - - - - pg_replication_origin_progress - - pg_replication_origin_progress ( node_name text, flush boolean ) - pg_lsn - - - Returns the replay location for the given replication origin. The - parameter flush determines whether the - corresponding local transaction will be guaranteed to have been - flushed to disk or not. - - - - - - - pg_logical_emit_message - - pg_logical_emit_message ( transactional boolean, prefix text, content text , flush boolean DEFAULT false ) - pg_lsn - - - pg_logical_emit_message ( transactional boolean, prefix text, content bytea , flush boolean DEFAULT false ) - pg_lsn - - - Emits a logical decoding message. This can be used to pass generic - messages to logical decoding plugins through - WAL. The transactional parameter specifies if - the message should be part of the current transaction, or if it should - be written immediately and decoded as soon as the logical decoder - reads the record. The prefix parameter is a - textual prefix that can be used by logical decoding plugins to easily - recognize messages that are interesting for them. - The content parameter is the content of the - message, given either in text or binary form. - The flush parameter (default set to - false) controls if the message is immediately - flushed to WAL or not. flush has no effect - with transactional, as the message's WAL - record is flushed along with its transaction. - - - - - - - pg_sync_replication_slots - - pg_sync_replication_slots () - void - - - Synchronize the logical failover replication slots from the primary - server to the standby server. This function can only be executed on the - standby server. Temporary synced slots, if any, cannot be used for - logical decoding and must be dropped after promotion. See - for details. - Note that this function is primarily intended for testing and - debugging purposes and should be used with caution. Additionally, - this function cannot be executed if - - sync_replication_slots is enabled and the slotsync - worker is already running to perform the synchronization of slots. - - - - - If, after executing the function, - - hot_standby_feedback is disabled on - the standby or the physical slot configured in - - primary_slot_name is - removed, then it is possible that the necessary rows of the - synchronized slot will be removed by the VACUUM process on the primary - server, resulting in the synchronized slot becoming invalidated. - - - - - - - -

- - - - - Database Object Management Functions - - - The functions shown in calculate - the disk space usage of database objects, or assist in presentation - or understanding of usage results. bigint results - are measured in bytes. If an OID that does - not represent an existing object is passed to one of these - functions, NULL is returned. - - - - Database Object Size Functions - - - - - Function - - - Description - - - - - - - - - pg_column_size - - pg_column_size ( "any" ) - integer - - - Shows the number of bytes used to store any individual data value. If - applied directly to a table column value, this reflects any - compression that was done. - - - - - - - pg_column_compression - - pg_column_compression ( "any" ) - text - - - Shows the compression algorithm that was used to compress - an individual variable-length value. Returns NULL - if the value is not compressed. - - - - - - - pg_column_toast_chunk_id - - pg_column_toast_chunk_id ( "any" ) - oid - - - Shows the chunk_id of an on-disk - TOASTed value. Returns NULL - if the value is un-TOASTed or not on-disk. See - for more information about - TOAST. - - - - - - - pg_database_size - - pg_database_size ( name ) - bigint - - - pg_database_size ( oid ) - bigint - - - Computes the total disk space used by the database with the specified - name or OID. To use this function, you must - have CONNECT privilege on the specified database - (which is granted by default) or have privileges of - the pg_read_all_stats role. - - - - - - - pg_indexes_size - - pg_indexes_size ( regclass ) - bigint - - - Computes the total disk space used by indexes attached to the - specified table. - - - - - - - pg_relation_size - - pg_relation_size ( relation regclass , fork text ) - bigint - - - Computes the disk space used by one fork of the - specified relation. (Note that for most purposes it is more - convenient to use the higher-level - functions pg_total_relation_size - or pg_table_size, which sum the sizes of all - forks.) With one argument, this returns the size of the main data - fork of the relation. The second argument can be provided to specify - which fork to examine: - - - - main returns the size of the main - data fork of the relation. - - - - - fsm returns the size of the Free Space Map - (see ) associated with the relation. - - - - - vm returns the size of the Visibility Map - (see ) associated with the relation. - - - - - init returns the size of the initialization - fork, if any, associated with the relation. - - - - - - - - - - pg_size_bytes - - pg_size_bytes ( text ) - bigint - - - Converts a size in human-readable format (as returned - by pg_size_pretty) into bytes. Valid units are - bytes, B, kB, - MB, GB, TB, - and PB. - - - - - - - pg_size_pretty - - pg_size_pretty ( bigint ) - text - - - pg_size_pretty ( numeric ) - text - - - Converts a size in bytes into a more easily human-readable format with - size units (bytes, kB, MB, GB, TB, or PB as appropriate). Note that the - units are powers of 2 rather than powers of 10, so 1kB is 1024 bytes, - 1MB is 10242 = 1048576 bytes, and so on. - - - - - - - pg_table_size - - pg_table_size ( regclass ) - bigint - - - Computes the disk space used by the specified table, excluding indexes - (but including its TOAST table if any, free space map, and visibility - map). - - - - - - - pg_tablespace_size - - pg_tablespace_size ( name ) - bigint - - - pg_tablespace_size ( oid ) - bigint - - - Computes the total disk space used in the tablespace with the - specified name or OID. To use this function, you must - have CREATE privilege on the specified tablespace - or have privileges of the pg_read_all_stats role, - unless it is the default tablespace for the current database. - - - - - - - pg_total_relation_size - - pg_total_relation_size ( regclass ) - bigint - - - Computes the total disk space used by the specified table, including - all indexes and TOAST data. The result is - equivalent to pg_table_size - + pg_indexes_size. - - - - -

- - - The functions above that operate on tables or indexes accept a - regclass argument, which is simply the OID of the table or index - in the pg_class system catalog. You do not have to look up - the OID by hand, however, since the regclass data type's input - converter will do the work for you. See - for details. - - - - The functions shown in assist - in identifying the specific disk files associated with database objects. - - - - Database Object Location Functions - - - - - Function - - - Description - - - - - - - - - pg_relation_filenode - - pg_relation_filenode ( relation regclass ) - oid - - - Returns the filenode number currently assigned to the - specified relation. The filenode is the base component of the file - name(s) used for the relation (see - for more information). - For most relations the result is the same as - pg_class.relfilenode, - but for certain system catalogs relfilenode - is zero and this function must be used to get the correct value. The - function returns NULL if passed a relation that does not have storage, - such as a view. - - - - - - - pg_relation_filepath - - pg_relation_filepath ( relation regclass ) - text - - - Returns the entire file path name (relative to the database cluster's - data directory, PGDATA) of the relation. - - - - - - - pg_filenode_relation - - pg_filenode_relation ( tablespace oid, filenode oid ) - regclass - - - Returns a relation's OID given the tablespace OID and filenode it is - stored under. This is essentially the inverse mapping of - pg_relation_filepath. For a relation in the - database's default tablespace, the tablespace can be specified as zero. - Returns NULL if no relation in the current database - is associated with the given values. - - - - -

- - - lists functions used to manage - collations. - - - - Collation Management Functions - - - - - Function - - - Description - - - - - - - - - pg_collation_actual_version - - pg_collation_actual_version ( oid ) - text - - - Returns the actual version of the collation object as it is currently - installed in the operating system. If this is different from the - value in - pg_collation.collversion, - then objects depending on the collation might need to be rebuilt. See - also . - - - - - - - pg_database_collation_actual_version - - pg_database_collation_actual_version ( oid ) - text - - - Returns the actual version of the database's collation as it is currently - installed in the operating system. If this is different from the - value in - pg_database.datcollversion, - then objects depending on the collation might need to be rebuilt. See - also . - - - - - - - pg_import_system_collations - - pg_import_system_collations ( schema regnamespace ) - integer - - - Adds collations to the system - catalog pg_collation based on all the locales - it finds in the operating system. This is - what initdb uses; see - for more details. If additional - locales are installed into the operating system later on, this - function can be run again to add collations for the new locales. - Locales that match existing entries - in pg_collation will be skipped. (But - collation objects based on locales that are no longer present in the - operating system are not removed by this function.) - The schema parameter would typically - be pg_catalog, but that is not a requirement; the - collations could be installed into some other schema as well. The - function returns the number of new collation objects it created. - Use of this function is restricted to superusers. - - - - -

- - - lists functions used to - manipulate statistics. - These functions cannot be executed during recovery. - - - Changes made by these statistics manipulation functions are likely to be - overwritten by autovacuum (or manual - VACUUM or ANALYZE) and should be - considered temporary. - - - - - - Database Object Statistics Manipulation Functions - - - - - Function - - - Description - - - - - - - - - pg_restore_relation_stats - - pg_restore_relation_stats ( - VARIADIC kwargs "any" ) - boolean - - - Updates table-level statistics. Ordinarily, these statistics are - collected automatically or updated as a part of or , so it's not - necessary to call this function. However, it is useful after a - restore to enable the optimizer to choose better plans if - ANALYZE has not been run yet. - - - The tracked statistics may change from version to version, so - arguments are passed as pairs of argname - and argvalue in the form: - -SELECT pg_restore_relation_stats( - 'arg1name', 'arg1value'::arg1type, - 'arg2name', 'arg2value'::arg2type, - 'arg3name', 'arg3value'::arg3type); - - - - For example, to set the relpages and - reltuples values for the table - mytable: - -SELECT pg_restore_relation_stats( - 'schemaname', 'myschema', - 'relname', 'mytable', - 'relpages', 173::integer, - 'reltuples', 10000::real); - - - - The arguments schemaname and - relname are required, and specify the table. Other - arguments are the names and values of statistics corresponding to - certain columns in pg_class. - The currently-supported relation statistics are - relpages with a value of type - integer, reltuples with a value of - type real, relallvisible with a value - of type integer, and relallfrozen - with a value of type integer. - - - Additionally, this function accepts argument name - version of type integer, which - specifies the server version from which the statistics originated. - This is anticipated to be helpful in porting statistics from older - versions of PostgreSQL. - - - Minor errors are reported as a WARNING and - ignored, and remaining statistics will still be restored. If all - specified statistics are successfully restored, returns - true, otherwise false. - - - The caller must have the MAINTAIN privilege on the - table or be the owner of the database. - - - - - - - - - pg_clear_relation_stats - - pg_clear_relation_stats ( schemaname text, relname text ) - void - - - Clears table-level statistics for the given relation, as though the - table was newly created. - - - The caller must have the MAINTAIN privilege on the - table or be the owner of the database. - - - - - - - - pg_restore_attribute_stats - - pg_restore_attribute_stats ( - VARIADIC kwargs "any" ) - boolean - - - Creates or updates column-level statistics. Ordinarily, these - statistics are collected automatically or updated as a part of or , so it's not - necessary to call this function. However, it is useful after a - restore to enable the optimizer to choose better plans if - ANALYZE has not been run yet. - - - The tracked statistics may change from version to version, so - arguments are passed as pairs of argname - and argvalue in the form: - -SELECT pg_restore_attribute_stats( - 'arg1name', 'arg1value'::arg1type, - 'arg2name', 'arg2value'::arg2type, - 'arg3name', 'arg3value'::arg3type); - - - - For example, to set the avg_width and - null_frac values for the attribute - col1 of the table - mytable: - -SELECT pg_restore_attribute_stats( - 'schemaname', 'myschema', - 'relname', 'mytable', - 'attname', 'col1', - 'inherited', false, - 'avg_width', 125::integer, - 'null_frac', 0.5::real); - - - - The required arguments are schemaname and - relname with a value of type text - which specify the table; either attname with a - value of type text or attnum with a - value of type smallint, which specifies the column; and - inherited, which specifies whether the statistics - include values from child tables. Other arguments are the names and - values of statistics corresponding to columns in pg_stats. - - - Additionally, this function accepts argument name - version of type integer, which - specifies the server version from which the statistics originated. - This is anticipated to be helpful in porting statistics from older - versions of PostgreSQL. - - - Minor errors are reported as a WARNING and - ignored, and remaining statistics will still be restored. If all - specified statistics are successfully restored, returns - true, otherwise false. - - - The caller must have the MAINTAIN privilege on the - table or be the owner of the database. - - - - - - - - - pg_clear_attribute_stats - - pg_clear_attribute_stats ( - schemaname text, - relname text, - attname text, - inherited boolean ) - void - - - Clears column-level statistics for the given relation and - attribute, as though the table was newly created. - - - The caller must have the MAINTAIN privilege on - the table or be the owner of the database. - - - - - -

- - - lists functions that provide - information about the structure of partitioned tables. - - - - Partitioning Information Functions - - - - - Function - - - Description - - - - - - - - - pg_partition_tree - - pg_partition_tree ( regclass ) - setof record - ( relid regclass, - parentrelid regclass, - isleaf boolean, - level integer ) - - - Lists the tables or indexes in the partition tree of the - given partitioned table or partitioned index, with one row for each - partition. Information provided includes the OID of the partition, - the OID of its immediate parent, a boolean value telling if the - partition is a leaf, and an integer telling its level in the hierarchy. - The level value is 0 for the input table or index, 1 for its - immediate child partitions, 2 for their partitions, and so on. - Returns no rows if the relation does not exist or is not a partition - or partitioned table. - - - - - - - pg_partition_ancestors - - pg_partition_ancestors ( regclass ) - setof regclass - - - Lists the ancestor relations of the given partition, - including the relation itself. Returns no rows if the relation - does not exist or is not a partition or partitioned table. - - - - - - - pg_partition_root - - pg_partition_root ( regclass ) - regclass - - - Returns the top-most parent of the partition tree to which the given - relation belongs. Returns NULL if the relation - does not exist or is not a partition or partitioned table. - - - - -

- - - For example, to check the total size of the data contained in a - partitioned table measurement, one could use the - following query: - -SELECT pg_size_pretty(sum(pg_relation_size(relid))) AS total_size - FROM pg_partition_tree('measurement'); - - - - - - - Index Maintenance Functions - - - shows the functions - available for index maintenance tasks. (Note that these maintenance - tasks are normally done automatically by autovacuum; use of these - functions is only required in special cases.) - These functions cannot be executed during recovery. - Use of these functions is restricted to superusers and the owner - of the given index. - - - - Index Maintenance Functions - - - - - Function - - - Description - - - - - - - - - brin_summarize_new_values - - brin_summarize_new_values ( index regclass ) - integer - - - Scans the specified BRIN index to find page ranges in the base table - that are not currently summarized by the index; for any such range it - creates a new summary index tuple by scanning those table pages. - Returns the number of new page range summaries that were inserted - into the index. - - - - - - - brin_summarize_range - - brin_summarize_range ( index regclass, blockNumber bigint ) - integer - - - Summarizes the page range covering the given block, if not already - summarized. This is - like brin_summarize_new_values except that it - only processes the page range that covers the given table block number. - - - - - - - brin_desummarize_range - - brin_desummarize_range ( index regclass, blockNumber bigint ) - void - - - Removes the BRIN index tuple that summarizes the page range covering - the given table block, if there is one. - - - - - - - gin_clean_pending_list - - gin_clean_pending_list ( index regclass ) - bigint - - - Cleans up the pending list of the specified GIN index - by moving entries in it, in bulk, to the main GIN data structure. - Returns the number of pages removed from the pending list. - If the argument is a GIN index built with - the fastupdate option disabled, no cleanup happens - and the result is zero, because the index doesn't have a pending list. - See and - for details about the pending list and fastupdate - option. - - - - -

- - - - - Generic File Access Functions - - - The functions shown in provide native access to - files on the machine hosting the server. Only files within the - database cluster directory and the log_directory can be - accessed, unless the user is a superuser or is granted the role - pg_read_server_files. Use a relative path for files in - the cluster directory, and a path matching the log_directory - configuration setting for log files. - - - - Note that granting users the EXECUTE privilege on - pg_read_file(), or related functions, allows them the - ability to read any file on the server that the database server process can - read; these functions bypass all in-database privilege checks. This means - that, for example, a user with such access is able to read the contents of - the pg_authid table where authentication - information is stored, as well as read any table data in the database. - Therefore, granting access to these functions should be carefully - considered. - - - - When granting privilege on these functions, note that the table entries - showing optional parameters are mostly implemented as several physical - functions with different parameter lists. Privilege must be granted - separately on each such function, if it is to be - used. psql's \df command - can be useful to check what the actual function signatures are. - - - - Some of these functions take an optional missing_ok - parameter, which specifies the behavior when the file or directory does - not exist. If true, the function - returns NULL or an empty result set, as appropriate. - If false, an error is raised. (Failure conditions - other than file not found are reported as errors in any - case.) The default is false. - - - - Generic File Access Functions - - - - - Function - - - Description - - - - - - - - - pg_ls_dir - - pg_ls_dir ( dirname text , missing_ok boolean, include_dot_dirs boolean ) - setof text - - - Returns the names of all files (and directories and other special - files) in the specified - directory. The include_dot_dirs parameter - indicates whether . and .. are to be - included in the result set; the default is to exclude them. Including - them can be useful when missing_ok - is true, to distinguish an empty directory from a - non-existent directory. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - - - pg_ls_logdir - - pg_ls_logdir () - setof record - ( name text, - size bigint, - modification timestamp with time zone ) - - - Returns the name, size, and last modification time (mtime) of each - ordinary file in the server's log directory. Filenames beginning with - a dot, directories, and other special files are excluded. - - - This function is restricted to superusers and roles with privileges of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - pg_ls_waldir - - pg_ls_waldir () - setof record - ( name text, - size bigint, - modification timestamp with time zone ) - - - Returns the name, size, and last modification time (mtime) of each - ordinary file in the server's write-ahead log (WAL) directory. - Filenames beginning with a dot, directories, and other special files - are excluded. - - - This function is restricted to superusers and roles with privileges of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - pg_ls_logicalmapdir - - pg_ls_logicalmapdir () - setof record - ( name text, - size bigint, - modification timestamp with time zone ) - - - Returns the name, size, and last modification time (mtime) of each - ordinary file in the server's pg_logical/mappings - directory. Filenames beginning with a dot, directories, and other - special files are excluded. - - - This function is restricted to superusers and members of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - pg_ls_logicalsnapdir - - pg_ls_logicalsnapdir () - setof record - ( name text, - size bigint, - modification timestamp with time zone ) - - - Returns the name, size, and last modification time (mtime) of each - ordinary file in the server's pg_logical/snapshots - directory. Filenames beginning with a dot, directories, and other - special files are excluded. - - - This function is restricted to superusers and members of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - pg_ls_replslotdir - - pg_ls_replslotdir ( slot_name text ) - setof record - ( name text, - size bigint, - modification timestamp with time zone ) - - - Returns the name, size, and last modification time (mtime) of each - ordinary file in the server's pg_replslot/slot_name - directory, where slot_name is the name of the - replication slot provided as input of the function. Filenames beginning - with a dot, directories, and other special files are excluded. - - - This function is restricted to superusers and members of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - pg_ls_summariesdir - - pg_ls_summariesdir () - setof record - ( name text, - size bigint, - modification timestamp with time zone ) - - - Returns the name, size, and last modification time (mtime) of each - ordinary file in the server's WAL summaries directory - (pg_wal/summaries). Filenames beginning - with a dot, directories, and other special files are excluded. - - - This function is restricted to superusers and members of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - pg_ls_archive_statusdir - - pg_ls_archive_statusdir () - setof record - ( name text, - size bigint, - modification timestamp with time zone ) - - - Returns the name, size, and last modification time (mtime) of each - ordinary file in the server's WAL archive status directory - (pg_wal/archive_status). Filenames beginning - with a dot, directories, and other special files are excluded. - - - This function is restricted to superusers and members of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - - pg_ls_tmpdir - - pg_ls_tmpdir ( tablespace oid ) - setof record - ( name text, - size bigint, - modification timestamp with time zone ) - - - Returns the name, size, and last modification time (mtime) of each - ordinary file in the temporary file directory for the - specified tablespace. - If tablespace is not provided, - the pg_default tablespace is examined. Filenames - beginning with a dot, directories, and other special files are - excluded. - - - This function is restricted to superusers and members of - the pg_monitor role by default, but other users can - be granted EXECUTE to run the function. - - - - - - - pg_read_file - - pg_read_file ( filename text , offset bigint, length bigint , missing_ok boolean ) - text - - - Returns all or part of a text file, starting at the - given byte offset, returning at - most length bytes (less if the end of file is - reached first). If offset is negative, it is - relative to the end of the file. If offset - and length are omitted, the entire file is - returned. The bytes read from the file are interpreted as a string in - the database's encoding; an error is thrown if they are not valid in - that encoding. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - - - pg_read_binary_file - - pg_read_binary_file ( filename text , offset bigint, length bigint , missing_ok boolean ) - bytea - - - Returns all or part of a file. This function is identical to - pg_read_file except that it can read arbitrary - binary data, returning the result as bytea - not text; accordingly, no encoding checks are performed. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - In combination with the convert_from function, - this function can be used to read a text file in a specified encoding - and convert to the database's encoding: - -SELECT convert_from(pg_read_binary_file('file_in_utf8.txt'), 'UTF8'); - - - - - - - - pg_stat_file - - pg_stat_file ( filename text , missing_ok boolean ) - record - ( size bigint, - access timestamp with time zone, - modification timestamp with time zone, - change timestamp with time zone, - creation timestamp with time zone, - isdir boolean ) - - - Returns a record containing the file's size, last access time stamp, - last modification time stamp, last file status change time stamp (Unix - platforms only), file creation time stamp (Windows only), and a flag - indicating if it is a directory. - - - This function is restricted to superusers by default, but other users - can be granted EXECUTE to run the function. - - - - - -

- - - - - Advisory Lock Functions - - - The functions shown in - manage advisory locks. For details about proper use of these functions, - see . - - - - All these functions are intended to be used to lock application-defined - resources, which can be identified either by a single 64-bit key value or - two 32-bit key values (note that these two key spaces do not overlap). - If another session already holds a conflicting lock on the same resource - identifier, the functions will either wait until the resource becomes - available, or return a false result, as appropriate for - the function. - Locks can be either shared or exclusive: a shared lock does not conflict - with other shared locks on the same resource, only with exclusive locks. - Locks can be taken at session level (so that they are held until released - or the session ends) or at transaction level (so that they are held until - the current transaction ends; there is no provision for manual release). - Multiple session-level lock requests stack, so that if the same resource - identifier is locked three times there must then be three unlock requests - to release the resource in advance of session end. - - - - Advisory Lock Functions - - - - - Function - - - Description - - - - - - - - - pg_advisory_lock - - pg_advisory_lock ( key bigint ) - void - - - pg_advisory_lock ( key1 integer, key2 integer ) - void - - - Obtains an exclusive session-level advisory lock, waiting if necessary. - - - - - - - pg_advisory_lock_shared - - pg_advisory_lock_shared ( key bigint ) - void - - - pg_advisory_lock_shared ( key1 integer, key2 integer ) - void - - - Obtains a shared session-level advisory lock, waiting if necessary. - - - - - - - pg_advisory_unlock - - pg_advisory_unlock ( key bigint ) - boolean - - - pg_advisory_unlock ( key1 integer, key2 integer ) - boolean - - - Releases a previously-acquired exclusive session-level advisory lock. - Returns true if the lock is successfully released. - If the lock was not held, false is returned, and in - addition, an SQL warning will be reported by the server. - - - - - - - pg_advisory_unlock_all - - pg_advisory_unlock_all () - void - - - Releases all session-level advisory locks held by the current session. - (This function is implicitly invoked at session end, even if the - client disconnects ungracefully.) - - - - - - - pg_advisory_unlock_shared - - pg_advisory_unlock_shared ( key bigint ) - boolean - - - pg_advisory_unlock_shared ( key1 integer, key2 integer ) - boolean - - - Releases a previously-acquired shared session-level advisory lock. - Returns true if the lock is successfully released. - If the lock was not held, false is returned, and in - addition, an SQL warning will be reported by the server. - - - - - - - pg_advisory_xact_lock - - pg_advisory_xact_lock ( key bigint ) - void - - - pg_advisory_xact_lock ( key1 integer, key2 integer ) - void - - - Obtains an exclusive transaction-level advisory lock, waiting if - necessary. - - - - - - - pg_advisory_xact_lock_shared - - pg_advisory_xact_lock_shared ( key bigint ) - void - - - pg_advisory_xact_lock_shared ( key1 integer, key2 integer ) - void - - - Obtains a shared transaction-level advisory lock, waiting if - necessary. - - - - - - - pg_try_advisory_lock - - pg_try_advisory_lock ( key bigint ) - boolean - - - pg_try_advisory_lock ( key1 integer, key2 integer ) - boolean - - - Obtains an exclusive session-level advisory lock if available. - This will either obtain the lock immediately and - return true, or return false - without waiting if the lock cannot be acquired immediately. - - - - - - - pg_try_advisory_lock_shared - - pg_try_advisory_lock_shared ( key bigint ) - boolean - - - pg_try_advisory_lock_shared ( key1 integer, key2 integer ) - boolean - - - Obtains a shared session-level advisory lock if available. - This will either obtain the lock immediately and - return true, or return false - without waiting if the lock cannot be acquired immediately. - - - - - - - pg_try_advisory_xact_lock - - pg_try_advisory_xact_lock ( key bigint ) - boolean - - - pg_try_advisory_xact_lock ( key1 integer, key2 integer ) - boolean - - - Obtains an exclusive transaction-level advisory lock if available. - This will either obtain the lock immediately and - return true, or return false - without waiting if the lock cannot be acquired immediately. - - - - - - - pg_try_advisory_xact_lock_shared - - pg_try_advisory_xact_lock_shared ( key bigint ) - boolean - - - pg_try_advisory_xact_lock_shared ( key1 integer, key2 integer ) - boolean - - - Obtains a shared transaction-level advisory lock if available. - This will either obtain the lock immediately and - return true, or return false - without waiting if the lock cannot be acquired immediately. - - - - -

- - - - - - - Trigger Functions - - - While many uses of triggers involve user-written trigger functions, - PostgreSQL provides a few built-in trigger - functions that can be used directly in user-defined triggers. These - are summarized in . - (Additional built-in trigger functions exist, which implement foreign - key constraints and deferred index constraints. Those are not documented - here since users need not use them directly.) - - - - For more information about creating triggers, see - . - - - - Built-In Trigger Functions - - - - - Function - - - Description - - - Example Usage - - - - - - - - - suppress_redundant_updates_trigger - - suppress_redundant_updates_trigger ( ) - trigger - - - Suppresses do-nothing update operations. See below for details. - - - CREATE TRIGGER ... suppress_redundant_updates_trigger() - - - - - - - tsvector_update_trigger - - tsvector_update_trigger ( ) - trigger - - - Automatically updates a tsvector column from associated - plain-text document column(s). The text search configuration to use - is specified by name as a trigger argument. See - for details. - - - CREATE TRIGGER ... tsvector_update_trigger(tsvcol, 'pg_catalog.swedish', title, body) - - - - - - - tsvector_update_trigger_column - - tsvector_update_trigger_column ( ) - trigger - - - Automatically updates a tsvector column from associated - plain-text document column(s). The text search configuration to use - is taken from a regconfig column of the table. See - for details. - - - CREATE TRIGGER ... tsvector_update_trigger_column(tsvcol, tsconfigcol, title, body) - - - - -

- - - The suppress_redundant_updates_trigger function, - when applied as a row-level BEFORE UPDATE trigger, - will prevent any update that does not actually change the data in the - row from taking place. This overrides the normal behavior which always - performs a physical row update - regardless of whether or not the data has changed. (This normal behavior - makes updates run faster, since no checking is required, and is also - useful in certain cases.) - - - - Ideally, you should avoid running updates that don't actually - change the data in the record. Redundant updates can cost considerable - unnecessary time, especially if there are lots of indexes to alter, - and space in dead rows that will eventually have to be vacuumed. - However, detecting such situations in client code is not - always easy, or even possible, and writing expressions to detect - them can be error-prone. An alternative is to use - suppress_redundant_updates_trigger, which will skip - updates that don't change the data. You should use this with care, - however. The trigger takes a small but non-trivial time for each record, - so if most of the records affected by updates do actually change, - use of this trigger will make updates run slower on average. - - - - The suppress_redundant_updates_trigger function can be - added to a table like this: - -CREATE TRIGGER z_min_update -BEFORE UPDATE ON tablename -FOR EACH ROW EXECUTE FUNCTION suppress_redundant_updates_trigger(); - - In most cases, you need to fire this trigger last for each row, so that - it does not override other triggers that might wish to alter the row. - Bearing in mind that triggers fire in name order, you would therefore - choose a trigger name that comes after the name of any other trigger - you might have on the table. (Hence the z prefix in the - example.) - - - - - Event Trigger Functions - - - PostgreSQL provides these helper functions - to retrieve information from event triggers. - - - - For more information about event triggers, - see . - - - - Capturing Changes at Command End - - - pg_event_trigger_ddl_commands - - - -pg_event_trigger_ddl_commands () setof record - - - - pg_event_trigger_ddl_commands returns a list of - DDL commands executed by each user action, - when invoked in a function attached to a - ddl_command_end event trigger. If called in any other - context, an error is raised. - pg_event_trigger_ddl_commands returns one row for each - base command executed; some commands that are a single SQL sentence - may return more than one row. This function returns the following - columns: - - - - - - Name - Type - Description - - - - - - classid - oid - OID of catalog the object belongs in - - - objid - oid - OID of the object itself - - - objsubid - integer - Sub-object ID (e.g., attribute number for a column) - - - command_tag - text - Command tag - - - object_type - text - Type of the object - - - schema_name - text - - Name of the schema the object belongs in, if any; otherwise NULL. - No quoting is applied. - - - - object_identity - text - - Text rendering of the object identity, schema-qualified. Each - identifier included in the identity is quoted if necessary. - - - - in_extension - boolean - True if the command is part of an extension script - - - command - pg_ddl_command - - A complete representation of the command, in internal format. - This cannot be output directly, but it can be passed to other - functions to obtain different pieces of information about the - command. - - - - - - - - - - Processing Objects Dropped by a DDL Command - - - pg_event_trigger_dropped_objects - - - -pg_event_trigger_dropped_objects () setof record - - - - pg_event_trigger_dropped_objects returns a list of all objects - dropped by the command in whose sql_drop event it is called. - If called in any other context, an error is raised. - This function returns the following columns: - - - - - - Name - Type - Description - - - - - - classid - oid - OID of catalog the object belonged in - - - objid - oid - OID of the object itself - - - objsubid - integer - Sub-object ID (e.g., attribute number for a column) - - - original - boolean - True if this was one of the root object(s) of the deletion - - - normal - boolean - - True if there was a normal dependency relationship - in the dependency graph leading to this object - - - - is_temporary - boolean - - True if this was a temporary object - - - - object_type - text - Type of the object - - - schema_name - text - - Name of the schema the object belonged in, if any; otherwise NULL. - No quoting is applied. - - - - object_name - text - - Name of the object, if the combination of schema and name can be - used as a unique identifier for the object; otherwise NULL. - No quoting is applied, and name is never schema-qualified. - - - - object_identity - text - - Text rendering of the object identity, schema-qualified. Each - identifier included in the identity is quoted if necessary. - - - - address_names - text[] - - An array that, together with object_type and - address_args, can be used by - the pg_get_object_address function to - recreate the object address in a remote server containing an - identically named object of the same kind. - - - - address_args - text[] - - Complement for address_names - - - - - - - - - The pg_event_trigger_dropped_objects function can be used - in an event trigger like this: - -CREATE FUNCTION test_event_trigger_for_drops() - RETURNS event_trigger LANGUAGE plpgsql AS $$ -DECLARE - obj record; -BEGIN - FOR obj IN SELECT * FROM pg_event_trigger_dropped_objects() - LOOP - RAISE NOTICE '% dropped object: % %.% %', - tg_tag, - obj.object_type, - obj.schema_name, - obj.object_name, - obj.object_identity; - END LOOP; -END; -$$; -CREATE EVENT TRIGGER test_event_trigger_for_drops - ON sql_drop - EXECUTE FUNCTION test_event_trigger_for_drops(); - - - - - - Handling a Table Rewrite Event - - - The functions shown in - - provide information about a table for which a - table_rewrite event has just been called. - If called in any other context, an error is raised. - - - - Table Rewrite Information Functions - - - - - Function - - - Description - - - - - - - - - pg_event_trigger_table_rewrite_oid - - pg_event_trigger_table_rewrite_oid () - oid - - - Returns the OID of the table about to be rewritten. - - - - - - - pg_event_trigger_table_rewrite_reason - - pg_event_trigger_table_rewrite_reason () - integer - - - Returns a code explaining the reason(s) for rewriting. The value is - a bitmap built from the following values: 1 - (the table has changed its persistence), 2 - (default value of a column has changed), 4 - (a column has a new data type) and 8 - (the table access method has changed). - - - - -

- - - These functions can be used in an event trigger like this: - -CREATE FUNCTION test_event_trigger_table_rewrite_oid() - RETURNS event_trigger - LANGUAGE plpgsql AS -$$ -BEGIN - RAISE NOTICE 'rewriting table % for reason %', - pg_event_trigger_table_rewrite_oid()::regclass, - pg_event_trigger_table_rewrite_reason(); -END; -$$; - -CREATE EVENT TRIGGER test_table_rewrite_oid - ON table_rewrite - EXECUTE FUNCTION test_event_trigger_table_rewrite_oid(); - - - - - - - Statistics Information Functions - - - function - statistics - - - - PostgreSQL provides a function to inspect complex - statistics defined using the CREATE STATISTICS command. - - - - Inspecting MCV Lists - - - pg_mcv_list_items - - - -pg_mcv_list_items ( pg_mcv_list ) setof record - - - - pg_mcv_list_items returns a set of records describing - all items stored in a multi-column MCV list. It - returns the following columns: - - - - - - Name - Type - Description - - - - - - index - integer - index of the item in the MCV list - - - values - text[] - values stored in the MCV item - - - nulls - boolean[] - flags identifying NULL values - - - frequency - double precision - frequency of this MCV item - - - base_frequency - double precision - base frequency of this MCV item - - - - - - - - The pg_mcv_list_items function can be used like this: - - -SELECT m.* FROM pg_statistic_ext join pg_statistic_ext_data on (oid = stxoid), - pg_mcv_list_items(stxdmcv) m WHERE stxname = 'stts'; - - - Values of the pg_mcv_list type can be obtained only from the - pg_statistic_ext_data.stxdmcv - column. - - - - - - diff --git a/doc/src/sgml/func/allfiles.sgml b/doc/src/sgml/func/allfiles.sgml new file mode 100644 index 00000000000..ce11ef1d5d8 --- /dev/null +++ b/doc/src/sgml/func/allfiles.sgml @@ -0,0 +1,40 @@ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + diff --git a/doc/src/sgml/func/func-admin.sgml b/doc/src/sgml/func/func-admin.sgml new file mode 100644 index 00000000000..446fdfe56f4 --- /dev/null +++ b/doc/src/sgml/func/func-admin.sgml @@ -0,0 +1,2962 @@ + + System Administration Functions + + + The functions described in this section are used to control and + monitor a PostgreSQL installation. + + + + Configuration Settings Functions + + + SET + + + + SHOW + + + + configuration + of the server + functions + + + + shows the functions + available to query and alter run-time configuration parameters. + + + + Configuration Settings Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + current_setting + + current_setting ( setting_name text , missing_ok boolean ) + text + + + Returns the current value of the + setting setting_name. If there is no such + setting, current_setting throws an error + unless missing_ok is supplied and + is true (in which case NULL is returned). + This function corresponds to + the SQL command . + + + current_setting('datestyle') + ISO, MDY + + + + + + + set_config + + set_config ( + setting_name text, + new_value text, + is_local boolean ) + text + + + Sets the parameter setting_name + to new_value, and returns that value. + If is_local is true, the new + value will only apply during the current transaction. If you want the + new value to apply for the rest of the current session, + use false instead. This function corresponds to + the SQL command . + + + set_config accepts the NULL value for + new_value, but as settings cannot be null, it + is interpreted as a request to reset the setting to its default value. + + + set_config('log_statement_stats', 'off', false) + off + + + + +

+ + + + + Server Signaling Functions + + + signal + backend processes + + + + The functions shown in send control signals to + other server processes. Use of these functions is restricted to + superusers by default but access may be granted to others using + GRANT, with noted exceptions. + + + + Each of these functions returns true if + the signal was successfully sent and false + if sending the signal failed. + + + + Server Signaling Functions + + + + + Function + + + Description + + + + + + + + + pg_cancel_backend + + pg_cancel_backend ( pid integer ) + boolean + + + Cancels the current query of the session whose backend process has the + specified process ID. This is also allowed if the + calling role is a member of the role whose backend is being canceled or + the calling role has privileges of pg_signal_backend, + however only superusers can cancel superuser backends. + As an exception, roles with privileges of + pg_signal_autovacuum_worker are permitted to + cancel autovacuum worker processes, which are otherwise considered + superuser backends. + + + + + + + pg_log_backend_memory_contexts + + pg_log_backend_memory_contexts ( pid integer ) + boolean + + + Requests to log the memory contexts of the backend with the + specified process ID. This function can send the request to + backends and auxiliary processes except logger. These memory contexts + will be logged at + LOG message level. They will appear in + the server log based on the log configuration set + (see for more information), + but will not be sent to the client regardless of + . + + + + + + + pg_reload_conf + + pg_reload_conf () + boolean + + + Causes all processes of the PostgreSQL + server to reload their configuration files. (This is initiated by + sending a SIGHUP signal to the postmaster + process, which in turn sends SIGHUP to each + of its children.) You can use the + pg_file_settings, + pg_hba_file_rules and + pg_ident_file_mappings views + to check the configuration files for possible errors, before reloading. + + + + + + + pg_rotate_logfile + + pg_rotate_logfile () + boolean + + + Signals the log-file manager to switch to a new output file + immediately. This works only when the built-in log collector is + running, since otherwise there is no log-file manager subprocess. + + + + + + + pg_terminate_backend + + pg_terminate_backend ( pid integer, timeout bigint DEFAULT 0 ) + boolean + + + Terminates the session whose backend process has the + specified process ID. This is also allowed if the calling role + is a member of the role whose backend is being terminated or the + calling role has privileges of pg_signal_backend, + however only superusers can terminate superuser backends. + As an exception, roles with privileges of + pg_signal_autovacuum_worker are permitted to + terminate autovacuum worker processes, which are otherwise considered + superuser backends. + + + If timeout is not specified or zero, this + function returns true whether the process actually + terminates or not, indicating only that the sending of the signal was + successful. If the timeout is specified (in + milliseconds) and greater than zero, the function waits until the + process is actually terminated or until the given time has passed. If + the process is terminated, the function + returns true. On timeout, a warning is emitted and + false is returned. + + + + +

+ + + pg_cancel_backend and pg_terminate_backend + send signals (SIGINT or SIGTERM + respectively) to backend processes identified by process ID. + The process ID of an active backend can be found from + the pid column of the + pg_stat_activity view, or by listing the + postgres processes on the server (using + ps on Unix or the Task + Manager on Windows). + The role of an active backend can be found from the + usename column of the + pg_stat_activity view. + + + + pg_log_backend_memory_contexts can be used + to log the memory contexts of a backend process. For example: + +postgres=# SELECT pg_log_backend_memory_contexts(pg_backend_pid()); + pg_log_backend_memory_contexts +-------------------------------- + t +(1 row) + +One message for each memory context will be logged. For example: + +LOG: logging memory contexts of PID 10377 +STATEMENT: SELECT pg_log_backend_memory_contexts(pg_backend_pid()); +LOG: level: 1; TopMemoryContext: 80800 total in 6 blocks; 14432 free (5 chunks); 66368 used +LOG: level: 2; pgstat TabStatusArray lookup hash table: 8192 total in 1 blocks; 1408 free (0 chunks); 6784 used +LOG: level: 2; TopTransactionContext: 8192 total in 1 blocks; 7720 free (1 chunks); 472 used +LOG: level: 2; RowDescriptionContext: 8192 total in 1 blocks; 6880 free (0 chunks); 1312 used +LOG: level: 2; MessageContext: 16384 total in 2 blocks; 5152 free (0 chunks); 11232 used +LOG: level: 2; Operator class cache: 8192 total in 1 blocks; 512 free (0 chunks); 7680 used +LOG: level: 2; smgr relation table: 16384 total in 2 blocks; 4544 free (3 chunks); 11840 used +LOG: level: 2; TransactionAbortContext: 32768 total in 1 blocks; 32504 free (0 chunks); 264 used +... +LOG: level: 2; ErrorContext: 8192 total in 1 blocks; 7928 free (3 chunks); 264 used +LOG: Grand total: 1651920 bytes in 201 blocks; 622360 free (88 chunks); 1029560 used + + If there are more than 100 child contexts under the same parent, the first + 100 child contexts are logged, along with a summary of the remaining contexts. + Note that frequent calls to this function could incur significant overhead, + because it may generate a large number of log messages. + + + + + + Backup Control Functions + + + backup + + + + The functions shown in assist in making on-line backups. + These functions cannot be executed during recovery (except + pg_backup_start, + pg_backup_stop, + and pg_wal_lsn_diff). + + + + For details about proper usage of these functions, see + . + + + + Backup Control Functions + + + + + Function + + + Description + + + + + + + + + pg_create_restore_point + + pg_create_restore_point ( name text ) + pg_lsn + + + Creates a named marker record in the write-ahead log that can later be + used as a recovery target, and returns the corresponding write-ahead + log location. The given name can then be used with + to specify the point up to + which recovery will proceed. Avoid creating multiple restore points + with the same name, since recovery will stop at the first one whose + name matches the recovery target. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + + + pg_current_wal_flush_lsn + + pg_current_wal_flush_lsn () + pg_lsn + + + Returns the current write-ahead log flush location (see notes below). + + + + + + + pg_current_wal_insert_lsn + + pg_current_wal_insert_lsn () + pg_lsn + + + Returns the current write-ahead log insert location (see notes below). + + + + + + + pg_current_wal_lsn + + pg_current_wal_lsn () + pg_lsn + + + Returns the current write-ahead log write location (see notes below). + + + + + + + pg_backup_start + + pg_backup_start ( + label text + , fast boolean + ) + pg_lsn + + + Prepares the server to begin an on-line backup. The only required + parameter is an arbitrary user-defined label for the backup. + (Typically this would be the name under which the backup dump file + will be stored.) + If the optional second parameter is given as true, + it specifies executing pg_backup_start as quickly + as possible. This forces a fast checkpoint which will cause a + spike in I/O operations, slowing any concurrently executing queries. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + + + pg_backup_stop + + pg_backup_stop ( + wait_for_archive boolean + ) + record + ( lsn pg_lsn, + labelfile text, + spcmapfile text ) + + + Finishes performing an on-line backup. The desired contents of the + backup label file and the tablespace map file are returned as part of + the result of the function and must be written to files in the + backup area. These files must not be written to the live data directory + (doing so will cause PostgreSQL to fail to restart in the event of a + crash). + + + There is an optional parameter of type boolean. + If false, the function will return immediately after the backup is + completed, without waiting for WAL to be archived. This behavior is + only useful with backup software that independently monitors WAL + archiving. Otherwise, WAL required to make the backup consistent might + be missing and make the backup useless. By default or when this + parameter is true, pg_backup_stop will wait for + WAL to be archived when archiving is enabled. (On a standby, this + means that it will wait only when archive_mode = + always. If write activity on the primary is low, + it may be useful to run pg_switch_wal on the + primary in order to trigger an immediate segment switch.) + + + When executed on a primary, this function also creates a backup + history file in the write-ahead log archive area. The history file + includes the label given to pg_backup_start, the + starting and ending write-ahead log locations for the backup, and the + starting and ending times of the backup. After recording the ending + location, the current write-ahead log insertion point is automatically + advanced to the next write-ahead log file, so that the ending + write-ahead log file can be archived immediately to complete the + backup. + + + The result of the function is a single record. + The lsn column holds the backup's ending + write-ahead log location (which again can be ignored). The second + column returns the contents of the backup label file, and the third + column returns the contents of the tablespace map file. These must be + stored as part of the backup and are required as part of the restore + process. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + + + pg_switch_wal + + pg_switch_wal () + pg_lsn + + + Forces the server to switch to a new write-ahead log file, which + allows the current file to be archived (assuming you are using + continuous archiving). The result is the ending write-ahead log + location plus 1 within the just-completed write-ahead log file. If + there has been no write-ahead log activity since the last write-ahead + log switch, pg_switch_wal does nothing and + returns the start location of the write-ahead log file currently in + use. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + + + pg_walfile_name + + pg_walfile_name ( lsn pg_lsn ) + text + + + Converts a write-ahead log location to the name of the WAL file + holding that location. + + + + + + + pg_walfile_name_offset + + pg_walfile_name_offset ( lsn pg_lsn ) + record + ( file_name text, + file_offset integer ) + + + Converts a write-ahead log location to a WAL file name and byte offset + within that file. + + + + + + + pg_split_walfile_name + + pg_split_walfile_name ( file_name text ) + record + ( segment_number numeric, + timeline_id bigint ) + + + Extracts the sequence number and timeline ID from a WAL file + name. + + + + + + + pg_wal_lsn_diff + + pg_wal_lsn_diff ( lsn1 pg_lsn, lsn2 pg_lsn ) + numeric + + + Calculates the difference in bytes (lsn1 - lsn2) between two write-ahead log + locations. This can be used + with pg_stat_replication or some of the + functions shown in to + get the replication lag. + + + + +

+ + + pg_current_wal_lsn displays the current write-ahead + log write location in the same format used by the above functions. + Similarly, pg_current_wal_insert_lsn displays the + current write-ahead log insertion location + and pg_current_wal_flush_lsn displays the current + write-ahead log flush location. The insertion location is + the logical end of the write-ahead log at any instant, + while the write location is the end of what has actually been written out + from the server's internal buffers, and the flush location is the last + location known to be written to durable storage. The write location is the + end of what can be examined from outside the server, and is usually what + you want if you are interested in archiving partially-complete write-ahead + log files. The insertion and flush locations are made available primarily + for server debugging purposes. These are all read-only operations and do + not require superuser permissions. + + + + You can use pg_walfile_name_offset to extract the + corresponding write-ahead log file name and byte offset from + a pg_lsn value. For example: + +postgres=# SELECT * FROM pg_walfile_name_offset((pg_backup_stop()).lsn); + file_name | file_offset +--------------------------+------------- + 00000001000000000000000D | 4039624 +(1 row) + + Similarly, pg_walfile_name extracts just the write-ahead log file name. + + + + pg_split_walfile_name is useful to compute a + LSN from a file offset and WAL file name, for example: + +postgres=# \set file_name '000000010000000100C000AB' +postgres=# \set offset 256 +postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset AS lsn + FROM pg_split_walfile_name(:'file_name') pd, + pg_show_all_settings() ps + WHERE ps.name = 'wal_segment_size'; + lsn +--------------- + C001/AB000100 +(1 row) + + + + + + + Recovery Control Functions + + + The functions shown in provide information + about the current status of a standby server. + These functions may be executed both during recovery and in normal running. + + + + Recovery Information Functions + + + + + Function + + + Description + + + + + + + + + pg_is_in_recovery + + pg_is_in_recovery () + boolean + + + Returns true if recovery is still in progress. + + + + + + + pg_last_wal_receive_lsn + + pg_last_wal_receive_lsn () + pg_lsn + + + Returns the last write-ahead log location that has been received and + synced to disk by streaming replication. While streaming replication + is in progress this will increase monotonically. If recovery has + completed then this will remain static at the location of the last WAL + record received and synced to disk during recovery. If streaming + replication is disabled, or if it has not yet started, the function + returns NULL. + + + + + + + pg_last_wal_replay_lsn + + pg_last_wal_replay_lsn () + pg_lsn + + + Returns the last write-ahead log location that has been replayed + during recovery. If recovery is still in progress this will increase + monotonically. If recovery has completed then this will remain + static at the location of the last WAL record applied during recovery. + When the server has been started normally without recovery, the + function returns NULL. + + + + + + + pg_last_xact_replay_timestamp + + pg_last_xact_replay_timestamp () + timestamp with time zone + + + Returns the time stamp of the last transaction replayed during + recovery. This is the time at which the commit or abort WAL record + for that transaction was generated on the primary. If no transactions + have been replayed during recovery, the function + returns NULL. Otherwise, if recovery is still in + progress this will increase monotonically. If recovery has completed + then this will remain static at the time of the last transaction + applied during recovery. When the server has been started normally + without recovery, the function returns NULL. + + + + + + + pg_get_wal_resource_managers + + pg_get_wal_resource_managers () + setof record + ( rm_id integer, + rm_name text, + rm_builtin boolean ) + + + Returns the currently-loaded WAL resource managers in the system. The + column rm_builtin indicates whether it's a + built-in resource manager, or a custom resource manager loaded by an + extension. + + + + +

+ + + The functions shown in control the progress of recovery. + These functions may be executed only during recovery. + + + + Recovery Control Functions + + + + + Function + + + Description + + + + + + + + + pg_is_wal_replay_paused + + pg_is_wal_replay_paused () + boolean + + + Returns true if recovery pause is requested. + + + + + + + pg_get_wal_replay_pause_state + + pg_get_wal_replay_pause_state () + text + + + Returns recovery pause state. The return values are + not paused if pause is not requested, + pause requested if pause is requested but recovery is + not yet paused, and paused if the recovery is + actually paused. + + + + + + + pg_promote + + pg_promote ( wait boolean DEFAULT true, wait_seconds integer DEFAULT 60 ) + boolean + + + Promotes a standby server to primary status. + With wait set to true (the + default), the function waits until promotion is completed + or wait_seconds seconds have passed, and + returns true if promotion is successful + and false otherwise. + If wait is set to false, the + function returns true immediately after sending a + SIGUSR1 signal to the postmaster to trigger + promotion. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + + + pg_wal_replay_pause + + pg_wal_replay_pause () + void + + + Request to pause recovery. A request doesn't mean that recovery stops + right away. If you want a guarantee that recovery is actually paused, + you need to check for the recovery pause state returned by + pg_get_wal_replay_pause_state(). Note that + pg_is_wal_replay_paused() returns whether a request + is made. While recovery is paused, no further database changes are applied. + If hot standby is active, all new queries will see the same consistent + snapshot of the database, and no further query conflicts will be generated + until recovery is resumed. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + + + pg_wal_replay_resume + + pg_wal_replay_resume () + void + + + Restarts recovery if it was paused. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + +

+ + + pg_wal_replay_pause and + pg_wal_replay_resume cannot be executed while + a promotion is ongoing. If a promotion is triggered while recovery + is paused, the paused state ends and promotion continues. + + + + If streaming replication is disabled, the paused state may continue + indefinitely without a problem. If streaming replication is in + progress then WAL records will continue to be received, which will + eventually fill available disk space, depending upon the duration of + the pause, the rate of WAL generation and available disk space. + + + + + + Snapshot Synchronization Functions + + + PostgreSQL allows database sessions to synchronize their + snapshots. A snapshot determines which data is visible to the + transaction that is using the snapshot. Synchronized snapshots are + necessary when two or more sessions need to see identical content in the + database. If two sessions just start their transactions independently, + there is always a possibility that some third transaction commits + between the executions of the two START TRANSACTION commands, + so that one session sees the effects of that transaction and the other + does not. + + + + To solve this problem, PostgreSQL allows a transaction to + export the snapshot it is using. As long as the exporting + transaction remains open, other transactions can import its + snapshot, and thereby be guaranteed that they see exactly the same view + of the database that the first transaction sees. But note that any + database changes made by any one of these transactions remain invisible + to the other transactions, as is usual for changes made by uncommitted + transactions. So the transactions are synchronized with respect to + pre-existing data, but act normally for changes they make themselves. + + + + Snapshots are exported with the pg_export_snapshot function, + shown in , and + imported with the command. + + + + Snapshot Synchronization Functions + + + + + Function + + + Description + + + + + + + + + pg_export_snapshot + + pg_export_snapshot () + text + + + Saves the transaction's current snapshot and returns + a text string identifying the snapshot. This string must + be passed (outside the database) to clients that want to import the + snapshot. The snapshot is available for import only until the end of + the transaction that exported it. + + + A transaction can export more than one snapshot, if needed. Note that + doing so is only useful in READ COMMITTED + transactions, since in REPEATABLE READ and higher + isolation levels, transactions use the same snapshot throughout their + lifetime. Once a transaction has exported any snapshots, it cannot be + prepared with . + + + + + + pg_log_standby_snapshot + + pg_log_standby_snapshot () + pg_lsn + + + Take a snapshot of running transactions and write it to WAL, without + having to wait for bgwriter or checkpointer to log one. This is useful + for logical decoding on standby, as logical slot creation has to wait + until such a record is replayed on the standby. + + + + +

+ + + + + Replication Management Functions + + + The functions shown + in are for + controlling and interacting with replication features. + See , + , and + + for information about the underlying features. + Use of functions for replication origin is only allowed to the + superuser by default, but may be allowed to other users by using the + GRANT command. + Use of functions for replication slots is restricted to superusers + and users having REPLICATION privilege. + + + + Many of these functions have equivalent commands in the replication + protocol; see . + + + + The functions described in + , + , and + + are also relevant for replication. + + + + Replication Management Functions + + + + + Function + + + Description + + + + + + + + + pg_create_physical_replication_slot + + pg_create_physical_replication_slot ( slot_name name , immediately_reserve boolean, temporary boolean ) + record + ( slot_name name, + lsn pg_lsn ) + + + Creates a new physical replication slot named + slot_name. The name cannot be + pg_conflict_detection as it is reserved for the + conflict detection slot. The optional second parameter, + when true, specifies that the LSN for this + replication slot be reserved immediately; otherwise + the LSN is reserved on first connection from a streaming + replication client. Streaming changes from a physical slot is only + possible with the streaming-replication protocol — + see . The optional third + parameter, temporary, when set to true, specifies that + the slot should not be permanently stored to disk and is only meant + for use by the current session. Temporary slots are also + released upon any error. This function corresponds + to the replication protocol command CREATE_REPLICATION_SLOT + ... PHYSICAL. + + + + + + + pg_drop_replication_slot + + pg_drop_replication_slot ( slot_name name ) + void + + + Drops the physical or logical replication slot + named slot_name. Same as replication protocol + command DROP_REPLICATION_SLOT. + + + + + + + pg_create_logical_replication_slot + + pg_create_logical_replication_slot ( slot_name name, plugin name , temporary boolean, twophase boolean, failover boolean ) + record + ( slot_name name, + lsn pg_lsn ) + + + Creates a new logical (decoding) replication slot named + slot_name using the output plugin + plugin. The name cannot be + pg_conflict_detection as it is reserved for + the conflict detection slot. The optional third + parameter, temporary, when set to true, specifies that + the slot should not be permanently stored to disk and is only meant + for use by the current session. Temporary slots are also + released upon any error. The optional fourth parameter, + twophase, when set to true, specifies + that the decoding of prepared transactions is enabled for this + slot. The optional fifth parameter, + failover, when set to true, + specifies that this slot is enabled to be synced to the + standbys so that logical replication can be resumed after + failover. A call to this function has the same effect as + the replication protocol command + CREATE_REPLICATION_SLOT ... LOGICAL. + + + + + + + pg_copy_physical_replication_slot + + pg_copy_physical_replication_slot ( src_slot_name name, dst_slot_name name , temporary boolean ) + record + ( slot_name name, + lsn pg_lsn ) + + + Copies an existing physical replication slot named src_slot_name + to a physical replication slot named dst_slot_name. + The new slot name cannot be pg_conflict_detection, + as it is reserved for the conflict detection. + The copied physical slot starts to reserve WAL from the same LSN as the + source slot. + temporary is optional. If temporary + is omitted, the same value as the source slot is used. Copy of an + invalidated slot is not allowed. + + + + + + + pg_copy_logical_replication_slot + + pg_copy_logical_replication_slot ( src_slot_name name, dst_slot_name name , temporary boolean , plugin name ) + record + ( slot_name name, + lsn pg_lsn ) + + + Copies an existing logical replication slot + named src_slot_name to a logical replication + slot named dst_slot_name, optionally changing + the output plugin and persistence. The new slot name cannot be + pg_conflict_detection as it is reserved for + the conflict detection. The copied logical slot starts from the same + LSN as the source logical slot. Both + temporary and plugin are + optional; if they are omitted, the values of the source slot are used. + The failover option of the source logical slot + is not copied and is set to false by default. This + is to avoid the risk of being unable to continue logical replication + after failover to standby where the slot is being synchronized. Copy of + an invalidated slot is not allowed. + + + + + + + pg_logical_slot_get_changes + + pg_logical_slot_get_changes ( slot_name name, upto_lsn pg_lsn, upto_nchanges integer, VARIADIC options text[] ) + setof record + ( lsn pg_lsn, + xid xid, + data text ) + + + Returns changes in the slot slot_name, starting + from the point from which changes have been consumed last. If + upto_lsn + and upto_nchanges are NULL, + logical decoding will continue until end of WAL. If + upto_lsn is non-NULL, decoding will include only + those transactions which commit prior to the specified LSN. If + upto_nchanges is non-NULL, decoding will + stop when the number of rows produced by decoding exceeds + the specified value. Note, however, that the actual number of + rows returned may be larger, since this limit is only checked after + adding the rows produced when decoding each new transaction commit. + If the specified slot is a logical failover slot then the function will + not return until all physical slots specified in + synchronized_standby_slots + have confirmed WAL receipt. + + + + + + + pg_logical_slot_peek_changes + + pg_logical_slot_peek_changes ( slot_name name, upto_lsn pg_lsn, upto_nchanges integer, VARIADIC options text[] ) + setof record + ( lsn pg_lsn, + xid xid, + data text ) + + + Behaves just like + the pg_logical_slot_get_changes() function, + except that changes are not consumed; that is, they will be returned + again on future calls. + + + + + + + pg_logical_slot_get_binary_changes + + pg_logical_slot_get_binary_changes ( slot_name name, upto_lsn pg_lsn, upto_nchanges integer, VARIADIC options text[] ) + setof record + ( lsn pg_lsn, + xid xid, + data bytea ) + + + Behaves just like + the pg_logical_slot_get_changes() function, + except that changes are returned as bytea. + + + + + + + pg_logical_slot_peek_binary_changes + + pg_logical_slot_peek_binary_changes ( slot_name name, upto_lsn pg_lsn, upto_nchanges integer, VARIADIC options text[] ) + setof record + ( lsn pg_lsn, + xid xid, + data bytea ) + + + Behaves just like + the pg_logical_slot_peek_changes() function, + except that changes are returned as bytea. + + + + + + + pg_replication_slot_advance + + pg_replication_slot_advance ( slot_name name, upto_lsn pg_lsn ) + record + ( slot_name name, + end_lsn pg_lsn ) + + + Advances the current confirmed position of a replication slot named + slot_name. The slot will not be moved backwards, + and it will not be moved beyond the current insert location. Returns + the name of the slot and the actual position that it was advanced to. + The updated slot position information is written out at the next + checkpoint if any advancing is done. So in the event of a crash, the + slot may return to an earlier position. If the specified slot is a + logical failover slot then the function will not return until all + physical slots specified in + synchronized_standby_slots + have confirmed WAL receipt. + + + + + + + pg_replication_origin_create + + pg_replication_origin_create ( node_name text ) + oid + + + Creates a replication origin with the given external + name, and returns the internal ID assigned to it. + The name must be no longer than 512 bytes. + + + + + + + pg_replication_origin_drop + + pg_replication_origin_drop ( node_name text ) + void + + + Deletes a previously-created replication origin, including any + associated replay progress. + + + + + + + pg_replication_origin_oid + + pg_replication_origin_oid ( node_name text ) + oid + + + Looks up a replication origin by name and returns the internal ID. If + no such replication origin is found, NULL is + returned. + + + + + + + pg_replication_origin_session_setup + + pg_replication_origin_session_setup ( node_name text ) + void + + + Marks the current session as replaying from the given + origin, allowing replay progress to be tracked. + Can only be used if no origin is currently selected. + Use pg_replication_origin_session_reset to undo. + + + + + + + pg_replication_origin_session_reset + + pg_replication_origin_session_reset () + void + + + Cancels the effects + of pg_replication_origin_session_setup(). + + + + + + + pg_replication_origin_session_is_setup + + pg_replication_origin_session_is_setup () + boolean + + + Returns true if a replication origin has been selected in the + current session. + + + + + + + pg_replication_origin_session_progress + + pg_replication_origin_session_progress ( flush boolean ) + pg_lsn + + + Returns the replay location for the replication origin selected in + the current session. The parameter flush + determines whether the corresponding local transaction will be + guaranteed to have been flushed to disk or not. + + + + + + + pg_replication_origin_xact_setup + + pg_replication_origin_xact_setup ( origin_lsn pg_lsn, origin_timestamp timestamp with time zone ) + void + + + Marks the current transaction as replaying a transaction that has + committed at the given LSN and timestamp. Can + only be called when a replication origin has been selected + using pg_replication_origin_session_setup. + + + + + + + pg_replication_origin_xact_reset + + pg_replication_origin_xact_reset () + void + + + Cancels the effects of + pg_replication_origin_xact_setup(). + + + + + + + pg_replication_origin_advance + + pg_replication_origin_advance ( node_name text, lsn pg_lsn ) + void + + + Sets replication progress for the given node to the given + location. This is primarily useful for setting up the initial + location, or setting a new location after configuration changes and + similar. Be aware that careless use of this function can lead to + inconsistently replicated data. + + + + + + + pg_replication_origin_progress + + pg_replication_origin_progress ( node_name text, flush boolean ) + pg_lsn + + + Returns the replay location for the given replication origin. The + parameter flush determines whether the + corresponding local transaction will be guaranteed to have been + flushed to disk or not. + + + + + + + pg_logical_emit_message + + pg_logical_emit_message ( transactional boolean, prefix text, content text , flush boolean DEFAULT false ) + pg_lsn + + + pg_logical_emit_message ( transactional boolean, prefix text, content bytea , flush boolean DEFAULT false ) + pg_lsn + + + Emits a logical decoding message. This can be used to pass generic + messages to logical decoding plugins through + WAL. The transactional parameter specifies if + the message should be part of the current transaction, or if it should + be written immediately and decoded as soon as the logical decoder + reads the record. The prefix parameter is a + textual prefix that can be used by logical decoding plugins to easily + recognize messages that are interesting for them. + The content parameter is the content of the + message, given either in text or binary form. + The flush parameter (default set to + false) controls if the message is immediately + flushed to WAL or not. flush has no effect + with transactional, as the message's WAL + record is flushed along with its transaction. + + + + + + + pg_sync_replication_slots + + pg_sync_replication_slots () + void + + + Synchronize the logical failover replication slots from the primary + server to the standby server. This function can only be executed on the + standby server. Temporary synced slots, if any, cannot be used for + logical decoding and must be dropped after promotion. See + for details. + Note that this function is primarily intended for testing and + debugging purposes and should be used with caution. Additionally, + this function cannot be executed if + + sync_replication_slots is enabled and the slotsync + worker is already running to perform the synchronization of slots. + + + + + If, after executing the function, + + hot_standby_feedback is disabled on + the standby or the physical slot configured in + + primary_slot_name is + removed, then it is possible that the necessary rows of the + synchronized slot will be removed by the VACUUM process on the primary + server, resulting in the synchronized slot becoming invalidated. + + + + + + + +

+ + + + + Database Object Management Functions + + + The functions shown in calculate + the disk space usage of database objects, or assist in presentation + or understanding of usage results. bigint results + are measured in bytes. If an OID that does + not represent an existing object is passed to one of these + functions, NULL is returned. + + + + Database Object Size Functions + + + + + Function + + + Description + + + + + + + + + pg_column_size + + pg_column_size ( "any" ) + integer + + + Shows the number of bytes used to store any individual data value. If + applied directly to a table column value, this reflects any + compression that was done. + + + + + + + pg_column_compression + + pg_column_compression ( "any" ) + text + + + Shows the compression algorithm that was used to compress + an individual variable-length value. Returns NULL + if the value is not compressed. + + + + + + + pg_column_toast_chunk_id + + pg_column_toast_chunk_id ( "any" ) + oid + + + Shows the chunk_id of an on-disk + TOASTed value. Returns NULL + if the value is un-TOASTed or not on-disk. See + for more information about + TOAST. + + + + + + + pg_database_size + + pg_database_size ( name ) + bigint + + + pg_database_size ( oid ) + bigint + + + Computes the total disk space used by the database with the specified + name or OID. To use this function, you must + have CONNECT privilege on the specified database + (which is granted by default) or have privileges of + the pg_read_all_stats role. + + + + + + + pg_indexes_size + + pg_indexes_size ( regclass ) + bigint + + + Computes the total disk space used by indexes attached to the + specified table. + + + + + + + pg_relation_size + + pg_relation_size ( relation regclass , fork text ) + bigint + + + Computes the disk space used by one fork of the + specified relation. (Note that for most purposes it is more + convenient to use the higher-level + functions pg_total_relation_size + or pg_table_size, which sum the sizes of all + forks.) With one argument, this returns the size of the main data + fork of the relation. The second argument can be provided to specify + which fork to examine: + + + + main returns the size of the main + data fork of the relation. + + + + + fsm returns the size of the Free Space Map + (see ) associated with the relation. + + + + + vm returns the size of the Visibility Map + (see ) associated with the relation. + + + + + init returns the size of the initialization + fork, if any, associated with the relation. + + + + + + + + + + pg_size_bytes + + pg_size_bytes ( text ) + bigint + + + Converts a size in human-readable format (as returned + by pg_size_pretty) into bytes. Valid units are + bytes, B, kB, + MB, GB, TB, + and PB. + + + + + + + pg_size_pretty + + pg_size_pretty ( bigint ) + text + + + pg_size_pretty ( numeric ) + text + + + Converts a size in bytes into a more easily human-readable format with + size units (bytes, kB, MB, GB, TB, or PB as appropriate). Note that the + units are powers of 2 rather than powers of 10, so 1kB is 1024 bytes, + 1MB is 10242 = 1048576 bytes, and so on. + + + + + + + pg_table_size + + pg_table_size ( regclass ) + bigint + + + Computes the disk space used by the specified table, excluding indexes + (but including its TOAST table if any, free space map, and visibility + map). + + + + + + + pg_tablespace_size + + pg_tablespace_size ( name ) + bigint + + + pg_tablespace_size ( oid ) + bigint + + + Computes the total disk space used in the tablespace with the + specified name or OID. To use this function, you must + have CREATE privilege on the specified tablespace + or have privileges of the pg_read_all_stats role, + unless it is the default tablespace for the current database. + + + + + + + pg_total_relation_size + + pg_total_relation_size ( regclass ) + bigint + + + Computes the total disk space used by the specified table, including + all indexes and TOAST data. The result is + equivalent to pg_table_size + + pg_indexes_size. + + + + +

+ + + The functions above that operate on tables or indexes accept a + regclass argument, which is simply the OID of the table or index + in the pg_class system catalog. You do not have to look up + the OID by hand, however, since the regclass data type's input + converter will do the work for you. See + for details. + + + + The functions shown in assist + in identifying the specific disk files associated with database objects. + + + + Database Object Location Functions + + + + + Function + + + Description + + + + + + + + + pg_relation_filenode + + pg_relation_filenode ( relation regclass ) + oid + + + Returns the filenode number currently assigned to the + specified relation. The filenode is the base component of the file + name(s) used for the relation (see + for more information). + For most relations the result is the same as + pg_class.relfilenode, + but for certain system catalogs relfilenode + is zero and this function must be used to get the correct value. The + function returns NULL if passed a relation that does not have storage, + such as a view. + + + + + + + pg_relation_filepath + + pg_relation_filepath ( relation regclass ) + text + + + Returns the entire file path name (relative to the database cluster's + data directory, PGDATA) of the relation. + + + + + + + pg_filenode_relation + + pg_filenode_relation ( tablespace oid, filenode oid ) + regclass + + + Returns a relation's OID given the tablespace OID and filenode it is + stored under. This is essentially the inverse mapping of + pg_relation_filepath. For a relation in the + database's default tablespace, the tablespace can be specified as zero. + Returns NULL if no relation in the current database + is associated with the given values. + + + + +

+ + + lists functions used to manage + collations. + + + + Collation Management Functions + + + + + Function + + + Description + + + + + + + + + pg_collation_actual_version + + pg_collation_actual_version ( oid ) + text + + + Returns the actual version of the collation object as it is currently + installed in the operating system. If this is different from the + value in + pg_collation.collversion, + then objects depending on the collation might need to be rebuilt. See + also . + + + + + + + pg_database_collation_actual_version + + pg_database_collation_actual_version ( oid ) + text + + + Returns the actual version of the database's collation as it is currently + installed in the operating system. If this is different from the + value in + pg_database.datcollversion, + then objects depending on the collation might need to be rebuilt. See + also . + + + + + + + pg_import_system_collations + + pg_import_system_collations ( schema regnamespace ) + integer + + + Adds collations to the system + catalog pg_collation based on all the locales + it finds in the operating system. This is + what initdb uses; see + for more details. If additional + locales are installed into the operating system later on, this + function can be run again to add collations for the new locales. + Locales that match existing entries + in pg_collation will be skipped. (But + collation objects based on locales that are no longer present in the + operating system are not removed by this function.) + The schema parameter would typically + be pg_catalog, but that is not a requirement; the + collations could be installed into some other schema as well. The + function returns the number of new collation objects it created. + Use of this function is restricted to superusers. + + + + +

+ + + lists functions used to + manipulate statistics. + These functions cannot be executed during recovery. + + + Changes made by these statistics manipulation functions are likely to be + overwritten by autovacuum (or manual + VACUUM or ANALYZE) and should be + considered temporary. + + + + + + Database Object Statistics Manipulation Functions + + + + + Function + + + Description + + + + + + + + + pg_restore_relation_stats + + pg_restore_relation_stats ( + VARIADIC kwargs "any" ) + boolean + + + Updates table-level statistics. Ordinarily, these statistics are + collected automatically or updated as a part of or , so it's not + necessary to call this function. However, it is useful after a + restore to enable the optimizer to choose better plans if + ANALYZE has not been run yet. + + + The tracked statistics may change from version to version, so + arguments are passed as pairs of argname + and argvalue in the form: + +SELECT pg_restore_relation_stats( + 'arg1name', 'arg1value'::arg1type, + 'arg2name', 'arg2value'::arg2type, + 'arg3name', 'arg3value'::arg3type); + + + + For example, to set the relpages and + reltuples values for the table + mytable: + +SELECT pg_restore_relation_stats( + 'schemaname', 'myschema', + 'relname', 'mytable', + 'relpages', 173::integer, + 'reltuples', 10000::real); + + + + The arguments schemaname and + relname are required, and specify the table. Other + arguments are the names and values of statistics corresponding to + certain columns in pg_class. + The currently-supported relation statistics are + relpages with a value of type + integer, reltuples with a value of + type real, relallvisible with a value + of type integer, and relallfrozen + with a value of type integer. + + + Additionally, this function accepts argument name + version of type integer, which + specifies the server version from which the statistics originated. + This is anticipated to be helpful in porting statistics from older + versions of PostgreSQL. + + + Minor errors are reported as a WARNING and + ignored, and remaining statistics will still be restored. If all + specified statistics are successfully restored, returns + true, otherwise false. + + + The caller must have the MAINTAIN privilege on the + table or be the owner of the database. + + + + + + + + + pg_clear_relation_stats + + pg_clear_relation_stats ( schemaname text, relname text ) + void + + + Clears table-level statistics for the given relation, as though the + table was newly created. + + + The caller must have the MAINTAIN privilege on the + table or be the owner of the database. + + + + + + + + pg_restore_attribute_stats + + pg_restore_attribute_stats ( + VARIADIC kwargs "any" ) + boolean + + + Creates or updates column-level statistics. Ordinarily, these + statistics are collected automatically or updated as a part of or , so it's not + necessary to call this function. However, it is useful after a + restore to enable the optimizer to choose better plans if + ANALYZE has not been run yet. + + + The tracked statistics may change from version to version, so + arguments are passed as pairs of argname + and argvalue in the form: + +SELECT pg_restore_attribute_stats( + 'arg1name', 'arg1value'::arg1type, + 'arg2name', 'arg2value'::arg2type, + 'arg3name', 'arg3value'::arg3type); + + + + For example, to set the avg_width and + null_frac values for the attribute + col1 of the table + mytable: + +SELECT pg_restore_attribute_stats( + 'schemaname', 'myschema', + 'relname', 'mytable', + 'attname', 'col1', + 'inherited', false, + 'avg_width', 125::integer, + 'null_frac', 0.5::real); + + + + The required arguments are schemaname and + relname with a value of type text + which specify the table; either attname with a + value of type text or attnum with a + value of type smallint, which specifies the column; and + inherited, which specifies whether the statistics + include values from child tables. Other arguments are the names and + values of statistics corresponding to columns in pg_stats. + + + Additionally, this function accepts argument name + version of type integer, which + specifies the server version from which the statistics originated. + This is anticipated to be helpful in porting statistics from older + versions of PostgreSQL. + + + Minor errors are reported as a WARNING and + ignored, and remaining statistics will still be restored. If all + specified statistics are successfully restored, returns + true, otherwise false. + + + The caller must have the MAINTAIN privilege on the + table or be the owner of the database. + + + + + + + + + pg_clear_attribute_stats + + pg_clear_attribute_stats ( + schemaname text, + relname text, + attname text, + inherited boolean ) + void + + + Clears column-level statistics for the given relation and + attribute, as though the table was newly created. + + + The caller must have the MAINTAIN privilege on + the table or be the owner of the database. + + + + + +

+ + + lists functions that provide + information about the structure of partitioned tables. + + + + Partitioning Information Functions + + + + + Function + + + Description + + + + + + + + + pg_partition_tree + + pg_partition_tree ( regclass ) + setof record + ( relid regclass, + parentrelid regclass, + isleaf boolean, + level integer ) + + + Lists the tables or indexes in the partition tree of the + given partitioned table or partitioned index, with one row for each + partition. Information provided includes the OID of the partition, + the OID of its immediate parent, a boolean value telling if the + partition is a leaf, and an integer telling its level in the hierarchy. + The level value is 0 for the input table or index, 1 for its + immediate child partitions, 2 for their partitions, and so on. + Returns no rows if the relation does not exist or is not a partition + or partitioned table. + + + + + + + pg_partition_ancestors + + pg_partition_ancestors ( regclass ) + setof regclass + + + Lists the ancestor relations of the given partition, + including the relation itself. Returns no rows if the relation + does not exist or is not a partition or partitioned table. + + + + + + + pg_partition_root + + pg_partition_root ( regclass ) + regclass + + + Returns the top-most parent of the partition tree to which the given + relation belongs. Returns NULL if the relation + does not exist or is not a partition or partitioned table. + + + + +

+ + + For example, to check the total size of the data contained in a + partitioned table measurement, one could use the + following query: + +SELECT pg_size_pretty(sum(pg_relation_size(relid))) AS total_size + FROM pg_partition_tree('measurement'); + + + + + + + Index Maintenance Functions + + + shows the functions + available for index maintenance tasks. (Note that these maintenance + tasks are normally done automatically by autovacuum; use of these + functions is only required in special cases.) + These functions cannot be executed during recovery. + Use of these functions is restricted to superusers and the owner + of the given index. + + + + Index Maintenance Functions + + + + + Function + + + Description + + + + + + + + + brin_summarize_new_values + + brin_summarize_new_values ( index regclass ) + integer + + + Scans the specified BRIN index to find page ranges in the base table + that are not currently summarized by the index; for any such range it + creates a new summary index tuple by scanning those table pages. + Returns the number of new page range summaries that were inserted + into the index. + + + + + + + brin_summarize_range + + brin_summarize_range ( index regclass, blockNumber bigint ) + integer + + + Summarizes the page range covering the given block, if not already + summarized. This is + like brin_summarize_new_values except that it + only processes the page range that covers the given table block number. + + + + + + + brin_desummarize_range + + brin_desummarize_range ( index regclass, blockNumber bigint ) + void + + + Removes the BRIN index tuple that summarizes the page range covering + the given table block, if there is one. + + + + + + + gin_clean_pending_list + + gin_clean_pending_list ( index regclass ) + bigint + + + Cleans up the pending list of the specified GIN index + by moving entries in it, in bulk, to the main GIN data structure. + Returns the number of pages removed from the pending list. + If the argument is a GIN index built with + the fastupdate option disabled, no cleanup happens + and the result is zero, because the index doesn't have a pending list. + See and + for details about the pending list and fastupdate + option. + + + + +

+ + + + + Generic File Access Functions + + + The functions shown in provide native access to + files on the machine hosting the server. Only files within the + database cluster directory and the log_directory can be + accessed, unless the user is a superuser or is granted the role + pg_read_server_files. Use a relative path for files in + the cluster directory, and a path matching the log_directory + configuration setting for log files. + + + + Note that granting users the EXECUTE privilege on + pg_read_file(), or related functions, allows them the + ability to read any file on the server that the database server process can + read; these functions bypass all in-database privilege checks. This means + that, for example, a user with such access is able to read the contents of + the pg_authid table where authentication + information is stored, as well as read any table data in the database. + Therefore, granting access to these functions should be carefully + considered. + + + + When granting privilege on these functions, note that the table entries + showing optional parameters are mostly implemented as several physical + functions with different parameter lists. Privilege must be granted + separately on each such function, if it is to be + used. psql's \df command + can be useful to check what the actual function signatures are. + + + + Some of these functions take an optional missing_ok + parameter, which specifies the behavior when the file or directory does + not exist. If true, the function + returns NULL or an empty result set, as appropriate. + If false, an error is raised. (Failure conditions + other than file not found are reported as errors in any + case.) The default is false. + + + + Generic File Access Functions + + + + + Function + + + Description + + + + + + + + + pg_ls_dir + + pg_ls_dir ( dirname text , missing_ok boolean, include_dot_dirs boolean ) + setof text + + + Returns the names of all files (and directories and other special + files) in the specified + directory. The include_dot_dirs parameter + indicates whether . and .. are to be + included in the result set; the default is to exclude them. Including + them can be useful when missing_ok + is true, to distinguish an empty directory from a + non-existent directory. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + + + pg_ls_logdir + + pg_ls_logdir () + setof record + ( name text, + size bigint, + modification timestamp with time zone ) + + + Returns the name, size, and last modification time (mtime) of each + ordinary file in the server's log directory. Filenames beginning with + a dot, directories, and other special files are excluded. + + + This function is restricted to superusers and roles with privileges of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + pg_ls_waldir + + pg_ls_waldir () + setof record + ( name text, + size bigint, + modification timestamp with time zone ) + + + Returns the name, size, and last modification time (mtime) of each + ordinary file in the server's write-ahead log (WAL) directory. + Filenames beginning with a dot, directories, and other special files + are excluded. + + + This function is restricted to superusers and roles with privileges of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + pg_ls_logicalmapdir + + pg_ls_logicalmapdir () + setof record + ( name text, + size bigint, + modification timestamp with time zone ) + + + Returns the name, size, and last modification time (mtime) of each + ordinary file in the server's pg_logical/mappings + directory. Filenames beginning with a dot, directories, and other + special files are excluded. + + + This function is restricted to superusers and members of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + pg_ls_logicalsnapdir + + pg_ls_logicalsnapdir () + setof record + ( name text, + size bigint, + modification timestamp with time zone ) + + + Returns the name, size, and last modification time (mtime) of each + ordinary file in the server's pg_logical/snapshots + directory. Filenames beginning with a dot, directories, and other + special files are excluded. + + + This function is restricted to superusers and members of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + pg_ls_replslotdir + + pg_ls_replslotdir ( slot_name text ) + setof record + ( name text, + size bigint, + modification timestamp with time zone ) + + + Returns the name, size, and last modification time (mtime) of each + ordinary file in the server's pg_replslot/slot_name + directory, where slot_name is the name of the + replication slot provided as input of the function. Filenames beginning + with a dot, directories, and other special files are excluded. + + + This function is restricted to superusers and members of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + pg_ls_summariesdir + + pg_ls_summariesdir () + setof record + ( name text, + size bigint, + modification timestamp with time zone ) + + + Returns the name, size, and last modification time (mtime) of each + ordinary file in the server's WAL summaries directory + (pg_wal/summaries). Filenames beginning + with a dot, directories, and other special files are excluded. + + + This function is restricted to superusers and members of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + pg_ls_archive_statusdir + + pg_ls_archive_statusdir () + setof record + ( name text, + size bigint, + modification timestamp with time zone ) + + + Returns the name, size, and last modification time (mtime) of each + ordinary file in the server's WAL archive status directory + (pg_wal/archive_status). Filenames beginning + with a dot, directories, and other special files are excluded. + + + This function is restricted to superusers and members of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + + pg_ls_tmpdir + + pg_ls_tmpdir ( tablespace oid ) + setof record + ( name text, + size bigint, + modification timestamp with time zone ) + + + Returns the name, size, and last modification time (mtime) of each + ordinary file in the temporary file directory for the + specified tablespace. + If tablespace is not provided, + the pg_default tablespace is examined. Filenames + beginning with a dot, directories, and other special files are + excluded. + + + This function is restricted to superusers and members of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + pg_read_file + + pg_read_file ( filename text , offset bigint, length bigint , missing_ok boolean ) + text + + + Returns all or part of a text file, starting at the + given byte offset, returning at + most length bytes (less if the end of file is + reached first). If offset is negative, it is + relative to the end of the file. If offset + and length are omitted, the entire file is + returned. The bytes read from the file are interpreted as a string in + the database's encoding; an error is thrown if they are not valid in + that encoding. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + + + pg_read_binary_file + + pg_read_binary_file ( filename text , offset bigint, length bigint , missing_ok boolean ) + bytea + + + Returns all or part of a file. This function is identical to + pg_read_file except that it can read arbitrary + binary data, returning the result as bytea + not text; accordingly, no encoding checks are performed. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + In combination with the convert_from function, + this function can be used to read a text file in a specified encoding + and convert to the database's encoding: + +SELECT convert_from(pg_read_binary_file('file_in_utf8.txt'), 'UTF8'); + + + + + + + + pg_stat_file + + pg_stat_file ( filename text , missing_ok boolean ) + record + ( size bigint, + access timestamp with time zone, + modification timestamp with time zone, + change timestamp with time zone, + creation timestamp with time zone, + isdir boolean ) + + + Returns a record containing the file's size, last access time stamp, + last modification time stamp, last file status change time stamp (Unix + platforms only), file creation time stamp (Windows only), and a flag + indicating if it is a directory. + + + This function is restricted to superusers by default, but other users + can be granted EXECUTE to run the function. + + + + + +

+ + + + + Advisory Lock Functions + + + The functions shown in + manage advisory locks. For details about proper use of these functions, + see . + + + + All these functions are intended to be used to lock application-defined + resources, which can be identified either by a single 64-bit key value or + two 32-bit key values (note that these two key spaces do not overlap). + If another session already holds a conflicting lock on the same resource + identifier, the functions will either wait until the resource becomes + available, or return a false result, as appropriate for + the function. + Locks can be either shared or exclusive: a shared lock does not conflict + with other shared locks on the same resource, only with exclusive locks. + Locks can be taken at session level (so that they are held until released + or the session ends) or at transaction level (so that they are held until + the current transaction ends; there is no provision for manual release). + Multiple session-level lock requests stack, so that if the same resource + identifier is locked three times there must then be three unlock requests + to release the resource in advance of session end. + + + + Advisory Lock Functions + + + + + Function + + + Description + + + + + + + + + pg_advisory_lock + + pg_advisory_lock ( key bigint ) + void + + + pg_advisory_lock ( key1 integer, key2 integer ) + void + + + Obtains an exclusive session-level advisory lock, waiting if necessary. + + + + + + + pg_advisory_lock_shared + + pg_advisory_lock_shared ( key bigint ) + void + + + pg_advisory_lock_shared ( key1 integer, key2 integer ) + void + + + Obtains a shared session-level advisory lock, waiting if necessary. + + + + + + + pg_advisory_unlock + + pg_advisory_unlock ( key bigint ) + boolean + + + pg_advisory_unlock ( key1 integer, key2 integer ) + boolean + + + Releases a previously-acquired exclusive session-level advisory lock. + Returns true if the lock is successfully released. + If the lock was not held, false is returned, and in + addition, an SQL warning will be reported by the server. + + + + + + + pg_advisory_unlock_all + + pg_advisory_unlock_all () + void + + + Releases all session-level advisory locks held by the current session. + (This function is implicitly invoked at session end, even if the + client disconnects ungracefully.) + + + + + + + pg_advisory_unlock_shared + + pg_advisory_unlock_shared ( key bigint ) + boolean + + + pg_advisory_unlock_shared ( key1 integer, key2 integer ) + boolean + + + Releases a previously-acquired shared session-level advisory lock. + Returns true if the lock is successfully released. + If the lock was not held, false is returned, and in + addition, an SQL warning will be reported by the server. + + + + + + + pg_advisory_xact_lock + + pg_advisory_xact_lock ( key bigint ) + void + + + pg_advisory_xact_lock ( key1 integer, key2 integer ) + void + + + Obtains an exclusive transaction-level advisory lock, waiting if + necessary. + + + + + + + pg_advisory_xact_lock_shared + + pg_advisory_xact_lock_shared ( key bigint ) + void + + + pg_advisory_xact_lock_shared ( key1 integer, key2 integer ) + void + + + Obtains a shared transaction-level advisory lock, waiting if + necessary. + + + + + + + pg_try_advisory_lock + + pg_try_advisory_lock ( key bigint ) + boolean + + + pg_try_advisory_lock ( key1 integer, key2 integer ) + boolean + + + Obtains an exclusive session-level advisory lock if available. + This will either obtain the lock immediately and + return true, or return false + without waiting if the lock cannot be acquired immediately. + + + + + + + pg_try_advisory_lock_shared + + pg_try_advisory_lock_shared ( key bigint ) + boolean + + + pg_try_advisory_lock_shared ( key1 integer, key2 integer ) + boolean + + + Obtains a shared session-level advisory lock if available. + This will either obtain the lock immediately and + return true, or return false + without waiting if the lock cannot be acquired immediately. + + + + + + + pg_try_advisory_xact_lock + + pg_try_advisory_xact_lock ( key bigint ) + boolean + + + pg_try_advisory_xact_lock ( key1 integer, key2 integer ) + boolean + + + Obtains an exclusive transaction-level advisory lock if available. + This will either obtain the lock immediately and + return true, or return false + without waiting if the lock cannot be acquired immediately. + + + + + + + pg_try_advisory_xact_lock_shared + + pg_try_advisory_xact_lock_shared ( key bigint ) + boolean + + + pg_try_advisory_xact_lock_shared ( key1 integer, key2 integer ) + boolean + + + Obtains a shared transaction-level advisory lock if available. + This will either obtain the lock immediately and + return true, or return false + without waiting if the lock cannot be acquired immediately. + + + + +

+ + + + diff --git a/doc/src/sgml/func/func-aggregate.sgml b/doc/src/sgml/func/func-aggregate.sgml new file mode 100644 index 00000000000..f50b692516b --- /dev/null +++ b/doc/src/sgml/func/func-aggregate.sgml @@ -0,0 +1,1418 @@ + + Aggregate Functions + + + aggregate function + built-in + + + + Aggregate functions compute a single result + from a set of input values. The built-in general-purpose aggregate + functions are listed in + while statistical aggregates are in . + The built-in within-group ordered-set aggregate functions + are listed in + while the built-in within-group hypothetical-set ones are in . Grouping operations, + which are closely related to aggregate functions, are listed in + . + The special syntax considerations for aggregate + functions are explained in . + Consult for additional introductory + information. + + + + Aggregate functions that support Partial Mode + are eligible to participate in various optimizations, such as parallel + aggregation. + + + + While all aggregates below accept an optional + ORDER BY clause (as outlined in ), the clause has only been added to + aggregates whose output is affected by ordering. + + + + General-Purpose Aggregate Functions + + + + + + + Function + + + Description + + Partial Mode + + + + + + + + any_value + + any_value ( anyelement ) + same as input type + + + Returns an arbitrary value from the non-null input values. + + Yes + + + + + + array_agg + + array_agg ( anynonarray ORDER BY input_sort_columns ) + anyarray + + + Collects all the input values, including nulls, into an array. + + Yes + + + + + array_agg ( anyarray ORDER BY input_sort_columns ) + anyarray + + + Concatenates all the input arrays into an array of one higher + dimension. (The inputs must all have the same dimensionality, and + cannot be empty or null.) + + Yes + + + + + + average + + + avg + + avg ( smallint ) + numeric + + + avg ( integer ) + numeric + + + avg ( bigint ) + numeric + + + avg ( numeric ) + numeric + + + avg ( real ) + double precision + + + avg ( double precision ) + double precision + + + avg ( interval ) + interval + + + Computes the average (arithmetic mean) of all the non-null input + values. + + Yes + + + + + + bit_and + + bit_and ( smallint ) + smallint + + + bit_and ( integer ) + integer + + + bit_and ( bigint ) + bigint + + + bit_and ( bit ) + bit + + + Computes the bitwise AND of all non-null input values. + + Yes + + + + + + bit_or + + bit_or ( smallint ) + smallint + + + bit_or ( integer ) + integer + + + bit_or ( bigint ) + bigint + + + bit_or ( bit ) + bit + + + Computes the bitwise OR of all non-null input values. + + Yes + + + + + + bit_xor + + bit_xor ( smallint ) + smallint + + + bit_xor ( integer ) + integer + + + bit_xor ( bigint ) + bigint + + + bit_xor ( bit ) + bit + + + Computes the bitwise exclusive OR of all non-null input values. + Can be useful as a checksum for an unordered set of values. + + Yes + + + + + + bool_and + + bool_and ( boolean ) + boolean + + + Returns true if all non-null input values are true, otherwise false. + + Yes + + + + + + bool_or + + bool_or ( boolean ) + boolean + + + Returns true if any non-null input value is true, otherwise false. + + Yes + + + + + + count + + count ( * ) + bigint + + + Computes the number of input rows. + + Yes + + + + + count ( "any" ) + bigint + + + Computes the number of input rows in which the input value is not + null. + + Yes + + + + + + every + + every ( boolean ) + boolean + + + This is the SQL standard's equivalent to bool_and. + + Yes + + + + + + json_agg + + json_agg ( anyelement ORDER BY input_sort_columns ) + json + + + + jsonb_agg + + jsonb_agg ( anyelement ORDER BY input_sort_columns ) + jsonb + + + Collects all the input values, including nulls, into a JSON array. + Values are converted to JSON as per to_json + or to_jsonb. + + No + + + + + + json_agg_strict + + json_agg_strict ( anyelement ) + json + + + + jsonb_agg_strict + + jsonb_agg_strict ( anyelement ) + jsonb + + + Collects all the input values, skipping nulls, into a JSON array. + Values are converted to JSON as per to_json + or to_jsonb. + + No + + + + + json_arrayagg + json_arrayagg ( + value_expression + ORDER BY sort_expression + { NULL | ABSENT } ON NULL + RETURNING data_type FORMAT JSON ENCODING UTF8 ) + + + Behaves in the same way as json_array + but as an aggregate function so it only takes one + value_expression parameter. + If ABSENT ON NULL is specified, any NULL + values are omitted. + If ORDER BY is specified, the elements will + appear in the array in that order rather than in the input order. + + + SELECT json_arrayagg(v) FROM (VALUES(2),(1)) t(v) + [2, 1] + + No + + + + + json_objectagg + json_objectagg ( + { key_expression { VALUE | ':' } value_expression } + { NULL | ABSENT } ON NULL + { WITH | WITHOUT } UNIQUE KEYS + RETURNING data_type FORMAT JSON ENCODING UTF8 ) + + + Behaves like json_object, but as an + aggregate function, so it only takes one + key_expression and one + value_expression parameter. + + + SELECT json_objectagg(k:v) FROM (VALUES ('a'::text,current_date),('b',current_date + 1)) AS t(k,v) + { "a" : "2022-05-10", "b" : "2022-05-11" } + + No + + + + + + json_object_agg + + json_object_agg ( key + "any", value + "any" + ORDER BY input_sort_columns ) + json + + + + jsonb_object_agg + + jsonb_object_agg ( key + "any", value + "any" + ORDER BY input_sort_columns ) + jsonb + + + Collects all the key/value pairs into a JSON object. Key arguments + are coerced to text; value arguments are converted as per + to_json or to_jsonb. + Values can be null, but keys cannot. + + No + + + + + + json_object_agg_strict + + json_object_agg_strict ( + key "any", + value "any" ) + json + + + + jsonb_object_agg_strict + + jsonb_object_agg_strict ( + key "any", + value "any" ) + jsonb + + + Collects all the key/value pairs into a JSON object. Key arguments + are coerced to text; value arguments are converted as per + to_json or to_jsonb. + The key can not be null. If the + value is null then the entry is skipped, + + No + + + + + + json_object_agg_unique + + json_object_agg_unique ( + key "any", + value "any" ) + json + + + + jsonb_object_agg_unique + + jsonb_object_agg_unique ( + key "any", + value "any" ) + jsonb + + + Collects all the key/value pairs into a JSON object. Key arguments + are coerced to text; value arguments are converted as per + to_json or to_jsonb. + Values can be null, but keys cannot. + If there is a duplicate key an error is thrown. + + No + + + + + + json_object_agg_unique_strict + + json_object_agg_unique_strict ( + key "any", + value "any" ) + json + + + + jsonb_object_agg_unique_strict + + jsonb_object_agg_unique_strict ( + key "any", + value "any" ) + jsonb + + + Collects all the key/value pairs into a JSON object. Key arguments + are coerced to text; value arguments are converted as per + to_json or to_jsonb. + The key can not be null. If the + value is null then the entry is skipped. + If there is a duplicate key an error is thrown. + + No + + + + + + max + + max ( see text ) + same as input type + + + Computes the maximum of the non-null input + values. Available for any numeric, string, date/time, or enum type, + as well as bytea, inet, interval, + money, oid, pg_lsn, + tid, xid8, + and also arrays and composite types containing sortable data types. + + Yes + + + + + + min + + min ( see text ) + same as input type + + + Computes the minimum of the non-null input + values. Available for any numeric, string, date/time, or enum type, + as well as bytea, inet, interval, + money, oid, pg_lsn, + tid, xid8, + and also arrays and composite types containing sortable data types. + + Yes + + + + + + range_agg + + range_agg ( value + anyrange ) + anymultirange + + + range_agg ( value + anymultirange ) + anymultirange + + + Computes the union of the non-null input values. + + No + + + + + + range_intersect_agg + + range_intersect_agg ( value + anyrange ) + anyrange + + + range_intersect_agg ( value + anymultirange ) + anymultirange + + + Computes the intersection of the non-null input values. + + No + + + + + + string_agg + + string_agg ( value + text, delimiter text ) + text + + + string_agg ( value + bytea, delimiter bytea + ORDER BY input_sort_columns ) + bytea + + + Concatenates the non-null input values into a string. Each value + after the first is preceded by the + corresponding delimiter (if it's not null). + + Yes + + + + + + sum + + sum ( smallint ) + bigint + + + sum ( integer ) + bigint + + + sum ( bigint ) + numeric + + + sum ( numeric ) + numeric + + + sum ( real ) + real + + + sum ( double precision ) + double precision + + + sum ( interval ) + interval + + + sum ( money ) + money + + + Computes the sum of the non-null input values. + + Yes + + + + + + xmlagg + + xmlagg ( xml ORDER BY input_sort_columns ) + xml + + + Concatenates the non-null XML input values (see + ). + + No + + + +

+ + + It should be noted that except for count, + these functions return a null value when no rows are selected. In + particular, sum of no rows returns null, not + zero as one might expect, and array_agg + returns null rather than an empty array when there are no input + rows. The coalesce function can be used to + substitute zero or an empty array for null when necessary. + + + + The aggregate functions array_agg, + json_agg, jsonb_agg, + json_agg_strict, jsonb_agg_strict, + json_object_agg, jsonb_object_agg, + json_object_agg_strict, jsonb_object_agg_strict, + json_object_agg_unique, jsonb_object_agg_unique, + json_object_agg_unique_strict, + jsonb_object_agg_unique_strict, + string_agg, + and xmlagg, as well as similar user-defined + aggregate functions, produce meaningfully different result values + depending on the order of the input values. This ordering is + unspecified by default, but can be controlled by writing an + ORDER BY clause within the aggregate call, as shown in + . + Alternatively, supplying the input values from a sorted subquery + will usually work. For example: + + + + Beware that this approach can fail if the outer query level contains + additional processing, such as a join, because that might cause the + subquery's output to be reordered before the aggregate is computed. + + + + + ANY + + + SOME + + + The boolean aggregates bool_and and + bool_or correspond to the standard SQL aggregates + every and any or + some. + PostgreSQL + supports every, but not any + or some, because there is an ambiguity built into + the standard syntax: + +SELECT b1 = ANY((SELECT b2 FROM t2 ...)) FROM t1 ...; + + Here ANY can be considered either as introducing + a subquery, or as being an aggregate function, if the subquery + returns one row with a Boolean value. + Thus the standard name cannot be given to these aggregates. + + + + + + Users accustomed to working with other SQL database management + systems might be disappointed by the performance of the + count aggregate when it is applied to the + entire table. A query like: + +SELECT count(*) FROM sometable; + + will require effort proportional to the size of the table: + PostgreSQL will need to scan either the + entire table or the entirety of an index that includes all rows in + the table. + + + + + shows + aggregate functions typically used in statistical analysis. + (These are separated out merely to avoid cluttering the listing + of more-commonly-used aggregates.) Functions shown as + accepting numeric_type are available for all + the types smallint, integer, + bigint, numeric, real, + and double precision. + Where the description mentions + N, it means the + number of input rows for which all the input expressions are non-null. + In all cases, null is returned if the computation is meaningless, + for example when N is zero. + + + + statistics + + + linear regression + + + + Aggregate Functions for Statistics + + + + + + + Function + + + Description + + Partial Mode + + + + + + + + correlation + + + corr + + corr ( Y double precision, X double precision ) + double precision + + + Computes the correlation coefficient. + + Yes + + + + + + covariance + population + + + covar_pop + + covar_pop ( Y double precision, X double precision ) + double precision + + + Computes the population covariance. + + Yes + + + + + + covariance + sample + + + covar_samp + + covar_samp ( Y double precision, X double precision ) + double precision + + + Computes the sample covariance. + + Yes + + + + + + regr_avgx + + regr_avgx ( Y double precision, X double precision ) + double precision + + + Computes the average of the independent variable, + sum(X)/N. + + Yes + + + + + + regr_avgy + + regr_avgy ( Y double precision, X double precision ) + double precision + + + Computes the average of the dependent variable, + sum(Y)/N. + + Yes + + + + + + regr_count + + regr_count ( Y double precision, X double precision ) + bigint + + + Computes the number of rows in which both inputs are non-null. + + Yes + + + + + + regression intercept + + + regr_intercept + + regr_intercept ( Y double precision, X double precision ) + double precision + + + Computes the y-intercept of the least-squares-fit linear equation + determined by the + (X, Y) pairs. + + Yes + + + + + + regr_r2 + + regr_r2 ( Y double precision, X double precision ) + double precision + + + Computes the square of the correlation coefficient. + + Yes + + + + + + regression slope + + + regr_slope + + regr_slope ( Y double precision, X double precision ) + double precision + + + Computes the slope of the least-squares-fit linear equation determined + by the (X, Y) + pairs. + + Yes + + + + + + regr_sxx + + regr_sxx ( Y double precision, X double precision ) + double precision + + + Computes the sum of squares of the independent + variable, + sum(X^2) - sum(X)^2/N. + + Yes + + + + + + regr_sxy + + regr_sxy ( Y double precision, X double precision ) + double precision + + + Computes the sum of products of independent times + dependent variables, + sum(X*Y) - sum(X) * sum(Y)/N. + + Yes + + + + + + regr_syy + + regr_syy ( Y double precision, X double precision ) + double precision + + + Computes the sum of squares of the dependent + variable, + sum(Y^2) - sum(Y)^2/N. + + Yes + + + + + + standard deviation + + + stddev + + stddev ( numeric_type ) + double precision + for real or double precision, + otherwise numeric + + + This is a historical alias for stddev_samp. + + Yes + + + + + + standard deviation + population + + + stddev_pop + + stddev_pop ( numeric_type ) + double precision + for real or double precision, + otherwise numeric + + + Computes the population standard deviation of the input values. + + Yes + + + + + + standard deviation + sample + + + stddev_samp + + stddev_samp ( numeric_type ) + double precision + for real or double precision, + otherwise numeric + + + Computes the sample standard deviation of the input values. + + Yes + + + + + + variance + + variance ( numeric_type ) + double precision + for real or double precision, + otherwise numeric + + + This is a historical alias for var_samp. + + Yes + + + + + + variance + population + + + var_pop + + var_pop ( numeric_type ) + double precision + for real or double precision, + otherwise numeric + + + Computes the population variance of the input values (square of the + population standard deviation). + + Yes + + + + + + variance + sample + + + var_samp + + var_samp ( numeric_type ) + double precision + for real or double precision, + otherwise numeric + + + Computes the sample variance of the input values (square of the sample + standard deviation). + + Yes + + + +

+ + + shows some + aggregate functions that use the ordered-set aggregate + syntax. These functions are sometimes referred to as inverse + distribution functions. Their aggregated input is introduced by + ORDER BY, and they may also take a direct + argument that is not aggregated, but is computed only once. + All these functions ignore null values in their aggregated input. + For those that take a fraction parameter, the + fraction value must be between 0 and 1; an error is thrown if not. + However, a null fraction value simply produces a + null result. + + + + ordered-set aggregate + built-in + + + inverse distribution + + + + Ordered-Set Aggregate Functions + + + + + + + Function + + + Description + + Partial Mode + + + + + + + + mode + statistical + + mode () WITHIN GROUP ( ORDER BY anyelement ) + anyelement + + + Computes the mode, the most frequent + value of the aggregated argument (arbitrarily choosing the first one + if there are multiple equally-frequent values). The aggregated + argument must be of a sortable type. + + No + + + + + + percentile + continuous + + percentile_cont ( fraction double precision ) WITHIN GROUP ( ORDER BY double precision ) + double precision + + + percentile_cont ( fraction double precision ) WITHIN GROUP ( ORDER BY interval ) + interval + + + Computes the continuous percentile, a value + corresponding to the specified fraction + within the ordered set of aggregated argument values. This will + interpolate between adjacent input items if needed. + + No + + + + + percentile_cont ( fractions double precision[] ) WITHIN GROUP ( ORDER BY double precision ) + double precision[] + + + percentile_cont ( fractions double precision[] ) WITHIN GROUP ( ORDER BY interval ) + interval[] + + + Computes multiple continuous percentiles. The result is an array of + the same dimensions as the fractions + parameter, with each non-null element replaced by the (possibly + interpolated) value corresponding to that percentile. + + No + + + + + + percentile + discrete + + percentile_disc ( fraction double precision ) WITHIN GROUP ( ORDER BY anyelement ) + anyelement + + + Computes the discrete percentile, the first + value within the ordered set of aggregated argument values whose + position in the ordering equals or exceeds the + specified fraction. The aggregated + argument must be of a sortable type. + + No + + + + + percentile_disc ( fractions double precision[] ) WITHIN GROUP ( ORDER BY anyelement ) + anyarray + + + Computes multiple discrete percentiles. The result is an array of the + same dimensions as the fractions parameter, + with each non-null element replaced by the input value corresponding + to that percentile. + The aggregated argument must be of a sortable type. + + No + + + +

+ + + hypothetical-set aggregate + built-in + + + + Each of the hypothetical-set aggregates listed in + is associated with a + window function of the same name defined in + . In each case, the aggregate's result + is the value that the associated window function would have + returned for the hypothetical row constructed from + args, if such a row had been added to the sorted + group of rows represented by the sorted_args. + For each of these functions, the list of direct arguments + given in args must match the number and types of + the aggregated arguments given in sorted_args. + Unlike most built-in aggregates, these aggregates are not strict, that is + they do not drop input rows containing nulls. Null values sort according + to the rule specified in the ORDER BY clause. + + + + Hypothetical-Set Aggregate Functions + + + + + + + Function + + + Description + + Partial Mode + + + + + + + + rank + hypothetical + + rank ( args ) WITHIN GROUP ( ORDER BY sorted_args ) + bigint + + + Computes the rank of the hypothetical row, with gaps; that is, the row + number of the first row in its peer group. + + No + + + + + + dense_rank + hypothetical + + dense_rank ( args ) WITHIN GROUP ( ORDER BY sorted_args ) + bigint + + + Computes the rank of the hypothetical row, without gaps; this function + effectively counts peer groups. + + No + + + + + + percent_rank + hypothetical + + percent_rank ( args ) WITHIN GROUP ( ORDER BY sorted_args ) + double precision + + + Computes the relative rank of the hypothetical row, that is + (rank - 1) / (total rows - 1). + The value thus ranges from 0 to 1 inclusive. + + No + + + + + + cume_dist + hypothetical + + cume_dist ( args ) WITHIN GROUP ( ORDER BY sorted_args ) + double precision + + + Computes the cumulative distribution, that is (number of rows + preceding or peers with hypothetical row) / (total rows). The value + thus ranges from 1/N to 1. + + No + + + +

+ + + Grouping Operations + + + + + Function + + + Description + + + + + + + + + GROUPING + + GROUPING ( group_by_expression(s) ) + integer + + + Returns a bit mask indicating which GROUP BY + expressions are not included in the current grouping set. + Bits are assigned with the rightmost argument corresponding to the + least-significant bit; each bit is 0 if the corresponding expression + is included in the grouping criteria of the grouping set generating + the current result row, and 1 if it is not included. + + + + +

+ + + The grouping operations shown in + are used in conjunction with + grouping sets (see ) to distinguish + result rows. The arguments to the GROUPING function + are not actually evaluated, but they must exactly match expressions given + in the GROUP BY clause of the associated query level. + For example: + +=> SELECT * FROM items_sold; + make | model | sales +-------+-------+------- + Foo | GT | 10 + Foo | Tour | 20 + Bar | City | 15 + Bar | Sport | 5 +(4 rows) + +=> SELECT make, model, GROUPING(make,model), sum(sales) FROM items_sold GROUP BY ROLLUP(make,model); + make | model | grouping | sum +-------+-------+----------+----- + Foo | GT | 0 | 10 + Foo | Tour | 0 | 20 + Bar | City | 0 | 15 + Bar | Sport | 0 | 5 + Foo | | 1 | 30 + Bar | | 1 | 20 + | | 3 | 50 +(7 rows) + + Here, the grouping value 0 in the + first four rows shows that those have been grouped normally, over both the + grouping columns. The value 1 indicates + that model was not grouped by in the next-to-last two + rows, and the value 3 indicates that + neither make nor model was grouped + by in the last row (which therefore is an aggregate over all the input + rows). + + + diff --git a/doc/src/sgml/func/func-array.sgml b/doc/src/sgml/func/func-array.sgml new file mode 100644 index 00000000000..97e4865a5f7 --- /dev/null +++ b/doc/src/sgml/func/func-array.sgml @@ -0,0 +1,646 @@ + + Array Functions and Operators + + + shows the specialized operators + available for array types. + In addition to those, the usual comparison operators shown in are available for + arrays. The comparison operators compare the array contents + element-by-element, using the default B-tree comparison function for + the element data type, and sort based on the first difference. + In multidimensional arrays the elements are visited in row-major order + (last subscript varies most rapidly). + If the contents of two arrays are equal but the dimensionality is + different, the first difference in the dimensionality information + determines the sort order. + + + + Array Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + anyarray @> anyarray + boolean + + + Does the first array contain the second, that is, does each element + appearing in the second array equal some element of the first array? + (Duplicates are not treated specially, + thus ARRAY[1] and ARRAY[1,1] are + each considered to contain the other.) + + + ARRAY[1,4,3] @> ARRAY[3,1,3] + t + + + + + + anyarray <@ anyarray + boolean + + + Is the first array contained by the second? + + + ARRAY[2,2,7] <@ ARRAY[1,7,4,2,6] + t + + + + + + anyarray && anyarray + boolean + + + Do the arrays overlap, that is, have any elements in common? + + + ARRAY[1,4,3] && ARRAY[2,1] + t + + + + + + anycompatiblearray || anycompatiblearray + anycompatiblearray + + + Concatenates the two arrays. Concatenating a null or empty array is a + no-op; otherwise the arrays must have the same number of dimensions + (as illustrated by the first example) or differ in number of + dimensions by one (as illustrated by the second). + If the arrays are not of identical element types, they will be coerced + to a common type (see ). + + + ARRAY[1,2,3] || ARRAY[4,5,6,7] + {1,2,3,4,5,6,7} + + + ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9.9]] + {{1,2,3},{4,5,6},{7,8,9.9}} + + + + + + anycompatible || anycompatiblearray + anycompatiblearray + + + Concatenates an element onto the front of an array (which must be + empty or one-dimensional). + + + 3 || ARRAY[4,5,6] + {3,4,5,6} + + + + + + anycompatiblearray || anycompatible + anycompatiblearray + + + Concatenates an element onto the end of an array (which must be + empty or one-dimensional). + + + ARRAY[4,5,6] || 7 + {4,5,6,7} + + + + +

+ + + See for more details about array operator + behavior. See for more details about + which operators support indexed operations. + + + + shows the functions + available for use with array types. See + for more information and examples of the use of these functions. + + + + Array Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + array_append + + array_append ( anycompatiblearray, anycompatible ) + anycompatiblearray + + + Appends an element to the end of an array (same as + the anycompatiblearray || anycompatible + operator). + + + array_append(ARRAY[1,2], 3) + {1,2,3} + + + + + + + array_cat + + array_cat ( anycompatiblearray, anycompatiblearray ) + anycompatiblearray + + + Concatenates two arrays (same as + the anycompatiblearray || anycompatiblearray + operator). + + + array_cat(ARRAY[1,2,3], ARRAY[4,5]) + {1,2,3,4,5} + + + + + + + array_dims + + array_dims ( anyarray ) + text + + + Returns a text representation of the array's dimensions. + + + array_dims(ARRAY[[1,2,3], [4,5,6]]) + [1:2][1:3] + + + + + + + array_fill + + array_fill ( anyelement, integer[] + , integer[] ) + anyarray + + + Returns an array filled with copies of the given value, having + dimensions of the lengths specified by the second argument. + The optional third argument supplies lower-bound values for each + dimension (which default to all 1). + + + array_fill(11, ARRAY[2,3]) + {{11,11,11},{11,11,11}} + + + array_fill(7, ARRAY[3], ARRAY[2]) + [2:4]={7,7,7} + + + + + + + array_length + + array_length ( anyarray, integer ) + integer + + + Returns the length of the requested array dimension. + (Produces NULL instead of 0 for empty or missing array dimensions.) + + + array_length(array[1,2,3], 1) + 3 + + + array_length(array[]::int[], 1) + NULL + + + array_length(array['text'], 2) + NULL + + + + + + + array_lower + + array_lower ( anyarray, integer ) + integer + + + Returns the lower bound of the requested array dimension. + + + array_lower('[0:2]={1,2,3}'::integer[], 1) + 0 + + + + + + + array_ndims + + array_ndims ( anyarray ) + integer + + + Returns the number of dimensions of the array. + + + array_ndims(ARRAY[[1,2,3], [4,5,6]]) + 2 + + + + + + + array_position + + array_position ( anycompatiblearray, anycompatible , integer ) + integer + + + Returns the subscript of the first occurrence of the second argument + in the array, or NULL if it's not present. + If the third argument is given, the search begins at that subscript. + The array must be one-dimensional. + Comparisons are done using IS NOT DISTINCT FROM + semantics, so it is possible to search for NULL. + + + array_position(ARRAY['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'], 'mon') + 2 + + + + + + + array_positions + + array_positions ( anycompatiblearray, anycompatible ) + integer[] + + + Returns an array of the subscripts of all occurrences of the second + argument in the array given as first argument. + The array must be one-dimensional. + Comparisons are done using IS NOT DISTINCT FROM + semantics, so it is possible to search for NULL. + NULL is returned only if the array + is NULL; if the value is not found in the array, an + empty array is returned. + + + array_positions(ARRAY['A','A','B','A'], 'A') + {1,2,4} + + + + + + + array_prepend + + array_prepend ( anycompatible, anycompatiblearray ) + anycompatiblearray + + + Prepends an element to the beginning of an array (same as + the anycompatible || anycompatiblearray + operator). + + + array_prepend(1, ARRAY[2,3]) + {1,2,3} + + + + + + + array_remove + + array_remove ( anycompatiblearray, anycompatible ) + anycompatiblearray + + + Removes all elements equal to the given value from the array. + The array must be one-dimensional. + Comparisons are done using IS NOT DISTINCT FROM + semantics, so it is possible to remove NULLs. + + + array_remove(ARRAY[1,2,3,2], 2) + {1,3} + + + + + + + array_replace + + array_replace ( anycompatiblearray, anycompatible, anycompatible ) + anycompatiblearray + + + Replaces each array element equal to the second argument with the + third argument. + + + array_replace(ARRAY[1,2,5,4], 5, 3) + {1,2,3,4} + + + + + + + array_reverse + + array_reverse ( anyarray ) + anyarray + + + Reverses the first dimension of the array. + + + array_reverse(ARRAY[[1,2],[3,4],[5,6]]) + {{5,6},{3,4},{1,2}} + + + + + + + array_sample + + array_sample ( array anyarray, n integer ) + anyarray + + + Returns an array of n items randomly selected + from array. n may not + exceed the length of array's first dimension. + If array is multi-dimensional, + an item is a slice having a given first subscript. + + + array_sample(ARRAY[1,2,3,4,5,6], 3) + {2,6,1} + + + array_sample(ARRAY[[1,2],[3,4],[5,6]], 2) + {{5,6},{1,2}} + + + + + + + array_shuffle + + array_shuffle ( anyarray ) + anyarray + + + Randomly shuffles the first dimension of the array. + + + array_shuffle(ARRAY[[1,2],[3,4],[5,6]]) + {{5,6},{1,2},{3,4}} + + + + + + + array_sort + + array_sort ( + array anyarray + , descending boolean + , nulls_first boolean + ) + anyarray + + + Sorts the first dimension of the array. + The sort order is determined by the default sort ordering of the + array's element type; however, if the element type is collatable, + the collation to use can be specified by adding + a COLLATE clause to + the array argument. + + + If descending is true then sort in + descending order, otherwise ascending order. If omitted, the + default is ascending order. + If nulls_first is true then nulls appear + before non-null values, otherwise nulls appear after non-null + values. + If omitted, nulls_first is taken to have + the same value as descending. + + + array_sort(ARRAY[[2,4],[2,1],[6,5]]) + {{2,1},{2,4},{6,5}} + + + + + + + array_to_string + + array_to_string ( array anyarray, delimiter text , null_string text ) + text + + + Converts each array element to its text representation, and + concatenates those separated by + the delimiter string. + If null_string is given and is + not NULL, then NULL array + entries are represented by that string; otherwise, they are omitted. + See also string_to_array. + + + array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*') + 1,2,3,*,5 + + + + + + + array_upper + + array_upper ( anyarray, integer ) + integer + + + Returns the upper bound of the requested array dimension. + + + array_upper(ARRAY[1,8,3,7], 1) + 4 + + + + + + + cardinality + + cardinality ( anyarray ) + integer + + + Returns the total number of elements in the array, or 0 if the array + is empty. + + + cardinality(ARRAY[[1,2],[3,4]]) + 4 + + + + + + + trim_array + + trim_array ( array anyarray, n integer ) + anyarray + + + Trims an array by removing the last n elements. + If the array is multidimensional, only the first dimension is trimmed. + + + trim_array(ARRAY[1,2,3,4,5,6], 2) + {1,2,3,4} + + + + + + + unnest + + unnest ( anyarray ) + setof anyelement + + + Expands an array into a set of rows. + The array's elements are read out in storage order. + + + unnest(ARRAY[1,2]) + + + 1 + 2 + + + + unnest(ARRAY[['foo','bar'],['baz','quux']]) + + + foo + bar + baz + quux + + + + + + + unnest ( anyarray, anyarray , ... ) + setof anyelement, anyelement [, ... ] + + + Expands multiple arrays (possibly of different data types) into a set of + rows. If the arrays are not all the same length then the shorter ones + are padded with NULLs. This form is only allowed + in a query's FROM clause; see . + + + select * from unnest(ARRAY[1,2], ARRAY['foo','bar','baz']) as x(a,b) + + + a | b +---+----- + 1 | foo + 2 | bar + | baz + + + + + +

+ + + See also about the aggregate + function array_agg for use with arrays. + + diff --git a/doc/src/sgml/func/func-binarystring.sgml b/doc/src/sgml/func/func-binarystring.sgml new file mode 100644 index 00000000000..78814ee0685 --- /dev/null +++ b/doc/src/sgml/func/func-binarystring.sgml @@ -0,0 +1,854 @@ + + Binary String Functions and Operators + + + binary data + functions + + + + This section describes functions and operators for examining and + manipulating binary strings, that is values of type bytea. + Many of these are equivalent, in purpose and syntax, to the + text-string functions described in the previous section. + + + + SQL defines some string functions that use + key words, rather than commas, to separate + arguments. Details are in + . + PostgreSQL also provides versions of these functions + that use the regular function invocation syntax + (see ). + + + + <acronym>SQL</acronym> Binary String Functions and Operators + + + + + Function/Operator + + + Description + + + Example(s) + + + + + + + + + binary string + concatenation + + bytea || bytea + bytea + + + Concatenates the two binary strings. + + + '\x123456'::bytea || '\x789a00bcde'::bytea + \x123456789a00bcde + + + + + + + bit_length + + bit_length ( bytea ) + integer + + + Returns number of bits in the binary string (8 + times the octet_length). + + + bit_length('\x123456'::bytea) + 24 + + + + + + + btrim + + btrim ( bytes bytea, + bytesremoved bytea ) + bytea + + + Removes the longest string containing only bytes appearing in + bytesremoved from the start and end of + bytes. + + + btrim('\x1234567890'::bytea, '\x9012'::bytea) + \x345678 + + + + + + + ltrim + + ltrim ( bytes bytea, + bytesremoved bytea ) + bytea + + + Removes the longest string containing only bytes appearing in + bytesremoved from the start of + bytes. + + + ltrim('\x1234567890'::bytea, '\x9012'::bytea) + \x34567890 + + + + + + + octet_length + + octet_length ( bytea ) + integer + + + Returns number of bytes in the binary string. + + + octet_length('\x123456'::bytea) + 3 + + + + + + + overlay + + overlay ( bytes bytea PLACING newsubstring bytea FROM start integer FOR count integer ) + bytea + + + Replaces the substring of bytes that starts at + the start'th byte and extends + for count bytes + with newsubstring. + If count is omitted, it defaults to the length + of newsubstring. + + + overlay('\x1234567890'::bytea placing '\002\003'::bytea from 2 for 3) + \x12020390 + + + + + + + position + + position ( substring bytea IN bytes bytea ) + integer + + + Returns first starting index of the specified + substring within + bytes, or zero if it's not present. + + + position('\x5678'::bytea in '\x1234567890'::bytea) + 3 + + + + + + + rtrim + + rtrim ( bytes bytea, + bytesremoved bytea ) + bytea + + + Removes the longest string containing only bytes appearing in + bytesremoved from the end of + bytes. + + + rtrim('\x1234567890'::bytea, '\x9012'::bytea) + \x12345678 + + + + + + + substring + + substring ( bytes bytea FROM start integer FOR count integer ) + bytea + + + Extracts the substring of bytes starting at + the start'th byte if that is specified, + and stopping after count bytes if that is + specified. Provide at least one of start + and count. + + + substring('\x1234567890'::bytea from 3 for 2) + \x5678 + + + + + + + trim + + trim ( LEADING | TRAILING | BOTH + bytesremoved bytea FROM + bytes bytea ) + bytea + + + Removes the longest string containing only bytes appearing in + bytesremoved from the start, + end, or both ends (BOTH is the default) + of bytes. + + + trim('\x9012'::bytea from '\x1234567890'::bytea) + \x345678 + + + + + + trim ( LEADING | TRAILING | BOTH FROM + bytes bytea, + bytesremoved bytea ) + bytea + + + This is a non-standard syntax for trim(). + + + trim(both from '\x1234567890'::bytea, '\x9012'::bytea) + \x345678 + + + + +

+ + + Additional binary string manipulation functions are available and + are listed in . Some + of them are used internally to implement the + SQL-standard string functions listed in . + + + + Other Binary String Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + bit_count + + + popcount + bit_count + + bit_count ( bytes bytea ) + bigint + + + Returns the number of bits set in the binary string (also known as + popcount). + + + bit_count('\x1234567890'::bytea) + 15 + + + + + + + crc32 + + crc32 ( bytea ) + bigint + + + Computes the CRC-32 value of the binary string. + + + crc32('abc'::bytea) + 891568578 + + + + + + + crc32c + + crc32c ( bytea ) + bigint + + + Computes the CRC-32C value of the binary string. + + + crc32c('abc'::bytea) + 910901175 + + + + + + + get_bit + + get_bit ( bytes bytea, + n bigint ) + integer + + + Extracts n'th bit + from binary string. + + + get_bit('\x1234567890'::bytea, 30) + 1 + + + + + + + get_byte + + get_byte ( bytes bytea, + n integer ) + integer + + + Extracts n'th byte + from binary string. + + + get_byte('\x1234567890'::bytea, 4) + 144 + + + + + + + length + + + binary string + length + + + length + of a binary string + binary strings, length + + length ( bytea ) + integer + + + Returns the number of bytes in the binary string. + + + length('\x1234567890'::bytea) + 5 + + + + + + length ( bytes bytea, + encoding name ) + integer + + + Returns the number of characters in the binary string, assuming + that it is text in the given encoding. + + + length('jose'::bytea, 'UTF8') + 4 + + + + + + + md5 + + md5 ( bytea ) + text + + + Computes the MD5 hash of + the binary string, with the result written in hexadecimal. + + + md5('Th\000omas'::bytea) + 8ab2d3c9689aaf18&zwsp;b4958c334c82d8b1 + + + + + + + reverse + + reverse ( bytea ) + bytea + + + Reverses the order of the bytes in the binary string. + + + reverse('\xabcd'::bytea) + \xcdab + + + + + + + set_bit + + set_bit ( bytes bytea, + n bigint, + newvalue integer ) + bytea + + + Sets n'th bit in + binary string to newvalue. + + + set_bit('\x1234567890'::bytea, 30, 0) + \x1234563890 + + + + + + + set_byte + + set_byte ( bytes bytea, + n integer, + newvalue integer ) + bytea + + + Sets n'th byte in + binary string to newvalue. + + + set_byte('\x1234567890'::bytea, 4, 64) + \x1234567840 + + + + + + + sha224 + + sha224 ( bytea ) + bytea + + + Computes the SHA-224 hash + of the binary string. + + + sha224('abc'::bytea) + \x23097d223405d8228642a477bda2&zwsp;55b32aadbce4bda0b3f7e36c9da7 + + + + + + + sha256 + + sha256 ( bytea ) + bytea + + + Computes the SHA-256 hash + of the binary string. + + + sha256('abc'::bytea) + \xba7816bf8f01cfea414140de5dae2223&zwsp;b00361a396177a9cb410ff61f20015ad + + + + + + + sha384 + + sha384 ( bytea ) + bytea + + + Computes the SHA-384 hash + of the binary string. + + + sha384('abc'::bytea) + \xcb00753f45a35e8bb5a03d699ac65007&zwsp;272c32ab0eded1631a8b605a43ff5bed&zwsp;8086072ba1e7cc2358baeca134c825a7 + + + + + + + sha512 + + sha512 ( bytea ) + bytea + + + Computes the SHA-512 hash + of the binary string. + + + sha512('abc'::bytea) + \xddaf35a193617abacc417349ae204131&zwsp;12e6fa4e89a97ea20a9eeee64b55d39a&zwsp;2192992a274fc1a836ba3c23a3feebbd&zwsp;454d4423643ce80e2a9ac94fa54ca49f + + + + + + + substr + + substr ( bytes bytea, start integer , count integer ) + bytea + + + Extracts the substring of bytes starting at + the start'th byte, + and extending for count bytes if that is + specified. (Same + as substring(bytes + from start + for count).) + + + substr('\x1234567890'::bytea, 3, 2) + \x5678 + + + + +

+ + + Functions get_byte and set_byte + number the first byte of a binary string as byte 0. + Functions get_bit and set_bit + number bits from the right within each byte; for example bit 0 is the least + significant bit of the first byte, and bit 15 is the most significant bit + of the second byte. + + + + For historical reasons, the function md5 + returns a hex-encoded value of type text whereas the SHA-2 + functions return type bytea. Use the functions + encode + and decode to + convert between the two. For example write encode(sha256('abc'), + 'hex') to get a hex-encoded text representation, + or decode(md5('abc'), 'hex') to get + a bytea value. + + + + + character string + converting to binary string + + + binary string + converting to character string + + Functions for converting strings between different character sets + (encodings), and for representing arbitrary binary data in textual + form, are shown in + . For these + functions, an argument or result of type text is expressed + in the database's default encoding, while arguments or results of + type bytea are in an encoding named by another argument. + + + + Text/Binary String Conversion Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + convert + + convert ( bytes bytea, + src_encoding name, + dest_encoding name ) + bytea + + + Converts a binary string representing text in + encoding src_encoding + to a binary string in encoding dest_encoding + (see for + available conversions). + + + convert('text_in_utf8', 'UTF8', 'LATIN1') + \x746578745f696e5f75746638 + + + + + + + convert_from + + convert_from ( bytes bytea, + src_encoding name ) + text + + + Converts a binary string representing text in + encoding src_encoding + to text in the database encoding + (see for + available conversions). + + + convert_from('text_in_utf8', 'UTF8') + text_in_utf8 + + + + + + + convert_to + + convert_to ( string text, + dest_encoding name ) + bytea + + + Converts a text string (in the database encoding) to a + binary string encoded in encoding dest_encoding + (see for + available conversions). + + + convert_to('some_text', 'UTF8') + \x736f6d655f74657874 + + + + + + + encode + + encode ( bytes bytea, + format text ) + text + + + Encodes binary data into a textual representation; supported + format values are: + base64, + escape, + hex. + + + encode('123\000\001', 'base64') + MTIzAAE= + + + + + + + decode + + decode ( string text, + format text ) + bytea + + + Decodes binary data from a textual representation; supported + format values are the same as + for encode. + + + decode('MTIzAAE=', 'base64') + \x3132330001 + + + + +

+ + + The encode and decode + functions support the following textual formats: + + + + base64 + + base64 format + + + + The base64 format is that + of RFC + 2045 Section 6.8. As per the RFC, encoded lines are + broken at 76 characters. However instead of the MIME CRLF + end-of-line marker, only a newline is used for end-of-line. + The decode function ignores carriage-return, + newline, space, and tab characters. Otherwise, an error is + raised when decode is supplied invalid + base64 data — including when trailing padding is incorrect. + + + + + + escape + + escape format + + + + The escape format converts zero bytes and + bytes with the high bit set into octal escape sequences + (\nnn), and it doubles + backslashes. Other byte values are represented literally. + The decode function will raise an error if a + backslash is not followed by either a second backslash or three + octal digits; it accepts other byte values unchanged. + + + + + + hex + + hex format + + + + The hex format represents each 4 bits of + data as one hexadecimal digit, 0 + through f, writing the higher-order digit of + each byte first. The encode function outputs + the a-f hex digits in lower + case. Because the smallest unit of data is 8 bits, there are + always an even number of characters returned + by encode. + The decode function + accepts the a-f characters in + either upper or lower case. An error is raised + when decode is given invalid hex data + — including when given an odd number of characters. + + + + + + + + In addition, it is possible to cast integral values to and from type + bytea. Casting an integer to bytea produces + 2, 4, or 8 bytes, depending on the width of the integer type. The result + is the two's complement representation of the integer, with the most + significant byte first. Some examples: + +1234::smallint::bytea \x04d2 +cast(1234 as bytea) \x000004d2 +cast(-1234 as bytea) \xfffffb2e +'\x8000'::bytea::smallint -32768 +'\x8000'::bytea::integer 32768 + + Casting a bytea to an integer will raise an error if the + length of the bytea exceeds the width of the integer type. + + + + See also the aggregate function string_agg in + and the large object functions + in . + + diff --git a/doc/src/sgml/func/func-bitstring.sgml b/doc/src/sgml/func/func-bitstring.sgml new file mode 100644 index 00000000000..f03dd63afcc --- /dev/null +++ b/doc/src/sgml/func/func-bitstring.sgml @@ -0,0 +1,358 @@ + + Bit String Functions and Operators + + + bit strings + functions + + + + This section describes functions and operators for examining and + manipulating bit strings, that is values of the types + bit and bit varying. (While only + type bit is mentioned in these tables, values of + type bit varying can be used interchangeably.) + Bit strings support the usual comparison operators shown in + , as well as the + operators shown in . + + + + Bit String Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + bit || bit + bit + + + Concatenation + + + B'10001' || B'011' + 10001011 + + + + + + bit & bit + bit + + + Bitwise AND (inputs must be of equal length) + + + B'10001' & B'01101' + 00001 + + + + + + bit | bit + bit + + + Bitwise OR (inputs must be of equal length) + + + B'10001' | B'01101' + 11101 + + + + + + bit # bit + bit + + + Bitwise exclusive OR (inputs must be of equal length) + + + B'10001' # B'01101' + 11100 + + + + + + ~ bit + bit + + + Bitwise NOT + + + ~ B'10001' + 01110 + + + + + + bit << integer + bit + + + Bitwise shift left + (string length is preserved) + + + B'10001' << 3 + 01000 + + + + + + bit >> integer + bit + + + Bitwise shift right + (string length is preserved) + + + B'10001' >> 2 + 00100 + + + + +

+ + + Some of the functions available for binary strings are also available + for bit strings, as shown in . + + + + Bit String Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + bit_count + + bit_count ( bit ) + bigint + + + Returns the number of bits set in the bit string (also known as + popcount). + + + bit_count(B'10111') + 4 + + + + + + + bit_length + + bit_length ( bit ) + integer + + + Returns number of bits in the bit string. + + + bit_length(B'10111') + 5 + + + + + + + length + + + bit string + length + + length ( bit ) + integer + + + Returns number of bits in the bit string. + + + length(B'10111') + 5 + + + + + + + octet_length + + octet_length ( bit ) + integer + + + Returns number of bytes in the bit string. + + + octet_length(B'1011111011') + 2 + + + + + + + overlay + + overlay ( bits bit PLACING newsubstring bit FROM start integer FOR count integer ) + bit + + + Replaces the substring of bits that starts at + the start'th bit and extends + for count bits + with newsubstring. + If count is omitted, it defaults to the length + of newsubstring. + + + overlay(B'01010101010101010' placing B'11111' from 2 for 3) + 0111110101010101010 + + + + + + + position + + position ( substring bit IN bits bit ) + integer + + + Returns first starting index of the specified substring + within bits, or zero if it's not present. + + + position(B'010' in B'000001101011') + 8 + + + + + + + substring + + substring ( bits bit FROM start integer FOR count integer ) + bit + + + Extracts the substring of bits starting at + the start'th bit if that is specified, + and stopping after count bits if that is + specified. Provide at least one of start + and count. + + + substring(B'110010111111' from 3 for 2) + 00 + + + + + + + get_bit + + get_bit ( bits bit, + n integer ) + integer + + + Extracts n'th bit + from bit string; the first (leftmost) bit is bit 0. + + + get_bit(B'101010101010101010', 6) + 1 + + + + + + + set_bit + + set_bit ( bits bit, + n integer, + newvalue integer ) + bit + + + Sets n'th bit in + bit string to newvalue; + the first (leftmost) bit is bit 0. + + + set_bit(B'101010101010101010', 6, 0) + 101010001010101010 + + + + +

+ + + In addition, it is possible to cast integral values to and from type + bit. + Casting an integer to bit(n) copies the rightmost + n bits. Casting an integer to a bit string width wider + than the integer itself will sign-extend on the left. + Some examples: + +44::bit(10) 0000101100 +44::bit(3) 100 +cast(-44 as bit(12)) 111111010100 +'1110'::bit(4)::integer 14 + + Note that casting to just bit means casting to + bit(1), and so will deliver only the least significant + bit of the integer. + + diff --git a/doc/src/sgml/func/func-comparison.sgml b/doc/src/sgml/func/func-comparison.sgml new file mode 100644 index 00000000000..c1205983f8b --- /dev/null +++ b/doc/src/sgml/func/func-comparison.sgml @@ -0,0 +1,638 @@ + + Comparison Functions and Operators + + + comparison + operators + + + + The usual comparison operators are available, as shown in . + + + + Comparison Operators + + + + Operator + Description + + + + + + + datatype < datatype + boolean + + Less than + + + + + datatype > datatype + boolean + + Greater than + + + + + datatype <= datatype + boolean + + Less than or equal to + + + + + datatype >= datatype + boolean + + Greater than or equal to + + + + + datatype = datatype + boolean + + Equal + + + + + datatype <> datatype + boolean + + Not equal + + + + + datatype != datatype + boolean + + Not equal + + + +

+ + + + <> is the standard SQL notation for not + equal. != is an alias, which is converted + to <> at a very early stage of parsing. + Hence, it is not possible to implement != + and <> operators that do different things. + + + + + These comparison operators are available for all built-in data types + that have a natural ordering, including numeric, string, and date/time + types. In addition, arrays, composite types, and ranges can be compared + if their component data types are comparable. + + + + It is usually possible to compare values of related data + types as well; for example integer > + bigint will work. Some cases of this sort are implemented + directly by cross-type comparison operators, but if no + such operator is available, the parser will coerce the less-general type + to the more-general type and apply the latter's comparison operator. + + + + As shown above, all comparison operators are binary operators that + return values of type boolean. Thus, expressions like + 1 < 2 < 3 are not valid (because there is + no < operator to compare a Boolean value with + 3). Use the BETWEEN predicates + shown below to perform range tests. + + + + There are also some comparison predicates, as shown in . These behave much like + operators, but have special syntax mandated by the SQL standard. + + + + Comparison Predicates + + + + + Predicate + + + Description + + + Example(s) + + + + + + + + datatype BETWEEN datatype AND datatype + boolean + + + Between (inclusive of the range endpoints). + + + 2 BETWEEN 1 AND 3 + t + + + 2 BETWEEN 3 AND 1 + f + + + + + + datatype NOT BETWEEN datatype AND datatype + boolean + + + Not between (the negation of BETWEEN). + + + 2 NOT BETWEEN 1 AND 3 + f + + + + + + datatype BETWEEN SYMMETRIC datatype AND datatype + boolean + + + Between, after sorting the two endpoint values. + + + 2 BETWEEN SYMMETRIC 3 AND 1 + t + + + + + + datatype NOT BETWEEN SYMMETRIC datatype AND datatype + boolean + + + Not between, after sorting the two endpoint values. + + + 2 NOT BETWEEN SYMMETRIC 3 AND 1 + f + + + + + + datatype IS DISTINCT FROM datatype + boolean + + + Not equal, treating null as a comparable value. + + + 1 IS DISTINCT FROM NULL + t (rather than NULL) + + + NULL IS DISTINCT FROM NULL + f (rather than NULL) + + + + + + datatype IS NOT DISTINCT FROM datatype + boolean + + + Equal, treating null as a comparable value. + + + 1 IS NOT DISTINCT FROM NULL + f (rather than NULL) + + + NULL IS NOT DISTINCT FROM NULL + t (rather than NULL) + + + + + + datatype IS NULL + boolean + + + Test whether value is null. + + + 1.5 IS NULL + f + + + + + + datatype IS NOT NULL + boolean + + + Test whether value is not null. + + + 'null' IS NOT NULL + t + + + + + + datatype ISNULL + boolean + + + Test whether value is null (nonstandard syntax). + + + + + + datatype NOTNULL + boolean + + + Test whether value is not null (nonstandard syntax). + + + + + + boolean IS TRUE + boolean + + + Test whether boolean expression yields true. + + + true IS TRUE + t + + + NULL::boolean IS TRUE + f (rather than NULL) + + + + + + boolean IS NOT TRUE + boolean + + + Test whether boolean expression yields false or unknown. + + + true IS NOT TRUE + f + + + NULL::boolean IS NOT TRUE + t (rather than NULL) + + + + + + boolean IS FALSE + boolean + + + Test whether boolean expression yields false. + + + true IS FALSE + f + + + NULL::boolean IS FALSE + f (rather than NULL) + + + + + + boolean IS NOT FALSE + boolean + + + Test whether boolean expression yields true or unknown. + + + true IS NOT FALSE + t + + + NULL::boolean IS NOT FALSE + t (rather than NULL) + + + + + + boolean IS UNKNOWN + boolean + + + Test whether boolean expression yields unknown. + + + true IS UNKNOWN + f + + + NULL::boolean IS UNKNOWN + t (rather than NULL) + + + + + + boolean IS NOT UNKNOWN + boolean + + + Test whether boolean expression yields true or false. + + + true IS NOT UNKNOWN + t + + + NULL::boolean IS NOT UNKNOWN + f (rather than NULL) + + + + +

+ + + + BETWEEN + + + BETWEEN SYMMETRIC + + The BETWEEN predicate simplifies range tests: + +a BETWEEN x AND y + + is equivalent to + +a >= x AND a <= y + + Notice that BETWEEN treats the endpoint values as included + in the range. + BETWEEN SYMMETRIC is like BETWEEN + except there is no requirement that the argument to the left of + AND be less than or equal to the argument on the right. + If it is not, those two arguments are automatically swapped, so that + a nonempty range is always implied. + + + + The various variants of BETWEEN are implemented in + terms of the ordinary comparison operators, and therefore will work for + any data type(s) that can be compared. + + + + + The use of AND in the BETWEEN + syntax creates an ambiguity with the use of AND as a + logical operator. To resolve this, only a limited set of expression + types are allowed as the second argument of a BETWEEN + clause. If you need to write a more complex sub-expression + in BETWEEN, write parentheses around the + sub-expression. + + + + + + IS DISTINCT FROM + + + IS NOT DISTINCT FROM + + Ordinary comparison operators yield null (signifying unknown), + not true or false, when either input is null. For example, + 7 = NULL yields null, as does 7 <> NULL. When + this behavior is not suitable, use the + IS NOT DISTINCT FROM predicates: + +a IS DISTINCT FROM b +a IS NOT DISTINCT FROM b + + For non-null inputs, IS DISTINCT FROM is + the same as the <> operator. However, if both + inputs are null it returns false, and if only one input is + null it returns true. Similarly, IS NOT DISTINCT + FROM is identical to = for non-null + inputs, but it returns true when both inputs are null, and false when only + one input is null. Thus, these predicates effectively act as though null + were a normal data value, rather than unknown. + + + + + IS NULL + + + IS NOT NULL + + + ISNULL + + + NOTNULL + + To check whether a value is or is not null, use the predicates: + +expression IS NULL +expression IS NOT NULL + + or the equivalent, but nonstandard, predicates: + +expression ISNULL +expression NOTNULL + + null valuecomparing + + + + Do not write + expression = NULL + because NULL is not equal to + NULL. (The null value represents an unknown value, + and it is not known whether two unknown values are equal.) + + + + + Some applications might expect that + expression = NULL + returns true if expression evaluates to + the null value. It is highly recommended that these applications + be modified to comply with the SQL standard. However, if that + cannot be done the + configuration variable is available. If it is enabled, + PostgreSQL will convert x = + NULL clauses to x IS NULL. + + + + + If the expression is row-valued, then + IS NULL is true when the row expression itself is null + or when all the row's fields are null, while + IS NOT NULL is true when the row expression itself is non-null + and all the row's fields are non-null. Because of this behavior, + IS NULL and IS NOT NULL do not always return + inverse results for row-valued expressions; in particular, a row-valued + expression that contains both null and non-null fields will return false + for both tests. For example: + + +SELECT ROW(1,2.5,'this is a test') = ROW(1, 3, 'not the same'); + +SELECT ROW(table.*) IS NULL FROM table; -- detect all-null rows + +SELECT ROW(table.*) IS NOT NULL FROM table; -- detect all-non-null rows + +SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in rows + + + In some cases, it may be preferable to + write row IS DISTINCT FROM NULL + or row IS NOT DISTINCT FROM NULL, + which will simply check whether the overall row value is null without any + additional tests on the row fields. + + + + + IS TRUE + + + IS NOT TRUE + + + IS FALSE + + + IS NOT FALSE + + + IS UNKNOWN + + + IS NOT UNKNOWN + + Boolean values can also be tested using the predicates + +boolean_expression IS TRUE +boolean_expression IS NOT TRUE +boolean_expression IS FALSE +boolean_expression IS NOT FALSE +boolean_expression IS UNKNOWN +boolean_expression IS NOT UNKNOWN + + These will always return true or false, never a null value, even when the + operand is null. + A null input is treated as the logical value unknown. + Notice that IS UNKNOWN and IS NOT UNKNOWN are + effectively the same as IS NULL and + IS NOT NULL, respectively, except that the input + expression must be of Boolean type. + + + + Some comparison-related functions are also available, as shown in . + + + + Comparison Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + num_nonnulls + + num_nonnulls ( VARIADIC "any" ) + integer + + + Returns the number of non-null arguments. + + + num_nonnulls(1, NULL, 2) + 2 + + + + + + num_nulls + + num_nulls ( VARIADIC "any" ) + integer + + + Returns the number of null arguments. + + + num_nulls(1, NULL, 2) + 1 + + + + +

+ + diff --git a/doc/src/sgml/func/func-comparisons.sgml b/doc/src/sgml/func/func-comparisons.sgml new file mode 100644 index 00000000000..6a6e0bd4019 --- /dev/null +++ b/doc/src/sgml/func/func-comparisons.sgml @@ -0,0 +1,336 @@ + + Row and Array Comparisons + + + IN + + + + NOT IN + + + + ANY + + + + ALL + + + + SOME + + + + composite type + comparison + + + + row-wise comparison + + + + comparison + composite type + + + + comparison + row constructor + + + + IS DISTINCT FROM + + + + IS NOT DISTINCT FROM + + + + This section describes several specialized constructs for making + multiple comparisons between groups of values. These forms are + syntactically related to the subquery forms of the previous section, + but do not involve subqueries. + The forms involving array subexpressions are + PostgreSQL extensions; the rest are + SQL-compliant. + All of the expression forms documented in this section return + Boolean (true/false) results. + + + + <literal>IN</literal> + + +expression IN (value , ...) + + + + The right-hand side is a parenthesized list + of expressions. The result is true if the left-hand expression's + result is equal to any of the right-hand expressions. This is a shorthand + notation for + + +expression = value1 +OR +expression = value2 +OR +... + + + + + Note that if the left-hand expression yields null, or if there are + no equal right-hand values and at least one right-hand expression yields + null, the result of the IN construct will be null, not false. + This is in accordance with SQL's normal rules for Boolean combinations + of null values. + + + + + <literal>NOT IN</literal> + + +expression NOT IN (value , ...) + + + + The right-hand side is a parenthesized list + of expressions. The result is true if the left-hand expression's + result is unequal to all of the right-hand expressions. This is a shorthand + notation for + + +expression <> value1 +AND +expression <> value2 +AND +... + + + + + Note that if the left-hand expression yields null, or if there are + no equal right-hand values and at least one right-hand expression yields + null, the result of the NOT IN construct will be null, not true + as one might naively expect. + This is in accordance with SQL's normal rules for Boolean combinations + of null values. + + + + + x NOT IN y is equivalent to NOT (x IN y) in all + cases. However, null values are much more likely to trip up the novice when + working with NOT IN than when working with IN. + It is best to express your condition positively if possible. + + + + + + <literal>ANY</literal>/<literal>SOME</literal> (array) + + +expression operator ANY (array expression) +expression operator SOME (array expression) + + + + The right-hand side is a parenthesized expression, which must yield an + array value. + The left-hand expression + is evaluated and compared to each element of the array using the + given operator, which must yield a Boolean + result. + The result of ANY is true if any true result is obtained. + The result is false if no true result is found (including the + case where the array has zero elements). + + + + If the array expression yields a null array, the result of + ANY will be null. If the left-hand expression yields null, + the result of ANY is ordinarily null (though a non-strict + comparison operator could possibly yield a different result). + Also, if the right-hand array contains any null elements and no true + comparison result is obtained, the result of ANY + will be null, not false (again, assuming a strict comparison operator). + This is in accordance with SQL's normal rules for Boolean combinations + of null values. + + + + SOME is a synonym for ANY. + + + + + <literal>ALL</literal> (array) + + +expression operator ALL (array expression) + + + + The right-hand side is a parenthesized expression, which must yield an + array value. + The left-hand expression + is evaluated and compared to each element of the array using the + given operator, which must yield a Boolean + result. + The result of ALL is true if all comparisons yield true + (including the case where the array has zero elements). + The result is false if any false result is found. + + + + If the array expression yields a null array, the result of + ALL will be null. If the left-hand expression yields null, + the result of ALL is ordinarily null (though a non-strict + comparison operator could possibly yield a different result). + Also, if the right-hand array contains any null elements and no false + comparison result is obtained, the result of ALL + will be null, not true (again, assuming a strict comparison operator). + This is in accordance with SQL's normal rules for Boolean combinations + of null values. + + + + + Row Constructor Comparison + + +row_constructor operator row_constructor + + + + Each side is a row constructor, + as described in . + The two row constructors must have the same number of fields. + The given operator is applied to each pair + of corresponding fields. (Since the fields could be of different + types, this means that a different specific operator could be selected + for each pair.) + All the selected operators must be members of some B-tree operator + class, or be the negator of an = member of a B-tree + operator class, meaning that row constructor comparison is only + possible when the operator is + =, + <>, + <, + <=, + >, or + >=, + or has semantics similar to one of these. + + + + The = and <> cases work slightly differently + from the others. Two rows are considered + equal if all their corresponding members are non-null and equal; the rows + are unequal if any corresponding members are non-null and unequal; + otherwise the result of the row comparison is unknown (null). + + + + For the <, <=, > and + >= cases, the row elements are compared left-to-right, + stopping as soon as an unequal or null pair of elements is found. + If either of this pair of elements is null, the result of the + row comparison is unknown (null); otherwise comparison of this pair + of elements determines the result. For example, + ROW(1,2,NULL) < ROW(1,3,0) + yields true, not null, because the third pair of elements are not + considered. + + + +row_constructor IS DISTINCT FROM row_constructor + + + + This construct is similar to a <> row comparison, + but it does not yield null for null inputs. Instead, any null value is + considered unequal to (distinct from) any non-null value, and any two + nulls are considered equal (not distinct). Thus the result will + either be true or false, never null. + + + +row_constructor IS NOT DISTINCT FROM row_constructor + + + + This construct is similar to a = row comparison, + but it does not yield null for null inputs. Instead, any null value is + considered unequal to (distinct from) any non-null value, and any two + nulls are considered equal (not distinct). Thus the result will always + be either true or false, never null. + + + + + + Composite Type Comparison + + +record operator record + + + + The SQL specification requires row-wise comparison to return NULL if the + result depends on comparing two NULL values or a NULL and a non-NULL. + PostgreSQL does this only when comparing the + results of two row constructors (as in + ) or comparing a row constructor + to the output of a subquery (as in ). + In other contexts where two composite-type values are compared, two + NULL field values are considered equal, and a NULL is considered larger + than a non-NULL. This is necessary in order to have consistent sorting + and indexing behavior for composite types. + + + + Each side is evaluated and they are compared row-wise. Composite type + comparisons are allowed when the operator is + =, + <>, + <, + <=, + > or + >=, + or has semantics similar to one of these. (To be specific, an operator + can be a row comparison operator if it is a member of a B-tree operator + class, or is the negator of the = member of a B-tree operator + class.) The default behavior of the above operators is the same as for + IS [ NOT ] DISTINCT FROM for row constructors (see + ). + + + + To support matching of rows which include elements without a default + B-tree operator class, the following operators are defined for composite + type comparison: + *=, + *<>, + *<, + *<=, + *>, and + *>=. + These operators compare the internal binary representation of the two + rows. Two rows might have a different binary representation even + though comparisons of the two rows with the equality operator is true. + The ordering of rows under these comparison operators is deterministic + but not otherwise meaningful. These operators are used internally + for materialized views and might be useful for other specialized + purposes such as replication and B-Tree deduplication (see ). They are not intended to be + generally useful for writing queries, though. + + + diff --git a/doc/src/sgml/func/func-conditional.sgml b/doc/src/sgml/func/func-conditional.sgml new file mode 100644 index 00000000000..7ca53dbf1ab --- /dev/null +++ b/doc/src/sgml/func/func-conditional.sgml @@ -0,0 +1,283 @@ + + Conditional Expressions + + + CASE + + + + conditional expression + + + + This section describes the SQL-compliant conditional expressions + available in PostgreSQL. + + + + + If your needs go beyond the capabilities of these conditional + expressions, you might want to consider writing a server-side function + in a more expressive programming language. + + + + + + Although COALESCE, GREATEST, and + LEAST are syntactically similar to functions, they are + not ordinary functions, and thus cannot be used with explicit + VARIADIC array arguments. + + + + + <literal>CASE</literal> + + + The SQL CASE expression is a + generic conditional expression, similar to if/else statements in + other programming languages: + + +CASE WHEN condition THEN result + WHEN ... + ELSE result +END + + + CASE clauses can be used wherever + an expression is valid. Each condition is an + expression that returns a boolean result. If the condition's + result is true, the value of the CASE expression is the + result that follows the condition, and the + remainder of the CASE expression is not processed. If the + condition's result is not true, any subsequent WHEN clauses + are examined in the same manner. If no WHEN + condition yields true, the value of the + CASE expression is the result of the + ELSE clause. If the ELSE clause is + omitted and no condition is true, the result is null. + + + + An example: + +SELECT * FROM test; + + a +--- + 1 + 2 + 3 + + +SELECT a, + CASE WHEN a=1 THEN 'one' + WHEN a=2 THEN 'two' + ELSE 'other' + END + FROM test; + + a | case +---+------- + 1 | one + 2 | two + 3 | other + + + + + The data types of all the result + expressions must be convertible to a single output type. + See for more details. + + + + There is a simple form of CASE expression + that is a variant of the general form above: + + +CASE expression + WHEN value THEN result + WHEN ... + ELSE result +END + + + The first + expression is computed, then compared to + each of the value expressions in the + WHEN clauses until one is found that is equal to it. If + no match is found, the result of the + ELSE clause (or a null value) is returned. This is similar + to the switch statement in C. + + + + The example above can be written using the simple + CASE syntax: + +SELECT a, + CASE a WHEN 1 THEN 'one' + WHEN 2 THEN 'two' + ELSE 'other' + END + FROM test; + + a | case +---+------- + 1 | one + 2 | two + 3 | other + + + + + A CASE expression does not evaluate any subexpressions + that are not needed to determine the result. For example, this is a + possible way of avoiding a division-by-zero failure: + +SELECT ... WHERE CASE WHEN x <> 0 THEN y/x > 1.5 ELSE false END; + + + + + + As described in , there are various + situations in which subexpressions of an expression are evaluated at + different times, so that the principle that CASE + evaluates only necessary subexpressions is not ironclad. For + example a constant 1/0 subexpression will usually result in + a division-by-zero failure at planning time, even if it's within + a CASE arm that would never be entered at run time. + + + + + + <literal>COALESCE</literal> + + + COALESCE + + + + NVL + + + + IFNULL + + + +COALESCE(value , ...) + + + + The COALESCE function returns the first of its + arguments that is not null. Null is returned only if all arguments + are null. It is often used to substitute a default value for + null values when data is retrieved for display, for example: + +SELECT COALESCE(description, short_description, '(none)') ... + + This returns description if it is not null, otherwise + short_description if it is not null, otherwise (none). + + + + The arguments must all be convertible to a common data type, which + will be the type of the result (see + for details). + + + + Like a CASE expression, COALESCE only + evaluates the arguments that are needed to determine the result; + that is, arguments to the right of the first non-null argument are + not evaluated. This SQL-standard function provides capabilities similar + to NVL and IFNULL, which are used in some other + database systems. + + + + + <literal>NULLIF</literal> + + + NULLIF + + + +NULLIF(value1, value2) + + + + The NULLIF function returns a null value if + value1 equals value2; + otherwise it returns value1. + This can be used to perform the inverse operation of the + COALESCE example given above: + +SELECT NULLIF(value, '(none)') ... + + In this example, if value is (none), + null is returned, otherwise the value of value + is returned. + + + + The two arguments must be of comparable types. + To be specific, they are compared exactly as if you had + written value1 + = value2, so there must be a + suitable = operator available. + + + + The result has the same type as the first argument — but there is + a subtlety. What is actually returned is the first argument of the + implied = operator, and in some cases that will have + been promoted to match the second argument's type. For + example, NULLIF(1, 2.2) yields numeric, + because there is no integer = + numeric operator, + only numeric = numeric. + + + + + + <literal>GREATEST</literal> and <literal>LEAST</literal> + + + GREATEST + + + LEAST + + + +GREATEST(value , ...) + + +LEAST(value , ...) + + + + The GREATEST and LEAST functions select the + largest or smallest value from a list of any number of expressions. + The expressions must all be convertible to a common data type, which + will be the type of the result + (see for details). + + + + NULL values in the argument list are ignored. The result will be NULL + only if all the expressions evaluate to NULL. (This is a deviation from + the SQL standard. According to the standard, the return value is NULL if + any argument is NULL. Some other databases behave this way.) + + + diff --git a/doc/src/sgml/func/func-datetime.sgml b/doc/src/sgml/func/func-datetime.sgml new file mode 100644 index 00000000000..482fe45f42e --- /dev/null +++ b/doc/src/sgml/func/func-datetime.sgml @@ -0,0 +1,2200 @@ + + Date/Time Functions and Operators + + + shows the available + functions for date/time value processing, with details appearing in + the following subsections. illustrates the behaviors of + the basic arithmetic operators (+, + *, etc.). For formatting functions, refer to + . You should be familiar with + the background information on date/time data types from . + + + + In addition, the usual comparison operators shown in + are available for the + date/time types. Dates and timestamps (with or without time zone) are + all comparable, while times (with or without time zone) and intervals + can only be compared to other values of the same data type. When + comparing a timestamp without time zone to a timestamp with time zone, + the former value is assumed to be given in the time zone specified by + the configuration parameter, and is + rotated to UTC for comparison to the latter value (which is already + in UTC internally). Similarly, a date value is assumed to represent + midnight in the TimeZone zone when comparing it + to a timestamp. + + + + All the functions and operators described below that take time or timestamp + inputs actually come in two variants: one that takes time with time zone or timestamp + with time zone, and one that takes time without time zone or timestamp without time zone. + For brevity, these variants are not shown separately. Also, the + + and * operators come in commutative pairs (for + example both date + integer + and integer + date); we show + only one of each such pair. + + + + Date/Time Operators + + + + + + Operator + + + Description + + + Example(s) + + + + + + + + date + integer + date + + + Add a number of days to a date + + + date '2001-09-28' + 7 + 2001-10-05 + + + + + + date + interval + timestamp + + + Add an interval to a date + + + date '2001-09-28' + interval '1 hour' + 2001-09-28 01:00:00 + + + + + + date + time + timestamp + + + Add a time-of-day to a date + + + date '2001-09-28' + time '03:00' + 2001-09-28 03:00:00 + + + + + + interval + interval + interval + + + Add intervals + + + interval '1 day' + interval '1 hour' + 1 day 01:00:00 + + + + + + timestamp + interval + timestamp + + + Add an interval to a timestamp + + + timestamp '2001-09-28 01:00' + interval '23 hours' + 2001-09-29 00:00:00 + + + + + + time + interval + time + + + Add an interval to a time + + + time '01:00' + interval '3 hours' + 04:00:00 + + + + + + - interval + interval + + + Negate an interval + + + - interval '23 hours' + -23:00:00 + + + + + + date - date + integer + + + Subtract dates, producing the number of days elapsed + + + date '2001-10-01' - date '2001-09-28' + 3 + + + + + + date - integer + date + + + Subtract a number of days from a date + + + date '2001-10-01' - 7 + 2001-09-24 + + + + + + date - interval + timestamp + + + Subtract an interval from a date + + + date '2001-09-28' - interval '1 hour' + 2001-09-27 23:00:00 + + + + + + time - time + interval + + + Subtract times + + + time '05:00' - time '03:00' + 02:00:00 + + + + + + time - interval + time + + + Subtract an interval from a time + + + time '05:00' - interval '2 hours' + 03:00:00 + + + + + + timestamp - interval + timestamp + + + Subtract an interval from a timestamp + + + timestamp '2001-09-28 23:00' - interval '23 hours' + 2001-09-28 00:00:00 + + + + + + interval - interval + interval + + + Subtract intervals + + + interval '1 day' - interval '1 hour' + 1 day -01:00:00 + + + + + + timestamp - timestamp + interval + + + Subtract timestamps (converting 24-hour intervals into days, + similarly to justify_hours()) + + + timestamp '2001-09-29 03:00' - timestamp '2001-07-27 12:00' + 63 days 15:00:00 + + + + + + interval * double precision + interval + + + Multiply an interval by a scalar + + + interval '1 second' * 900 + 00:15:00 + + + interval '1 day' * 21 + 21 days + + + interval '1 hour' * 3.5 + 03:30:00 + + + + + + interval / double precision + interval + + + Divide an interval by a scalar + + + interval '1 hour' / 1.5 + 00:40:00 + + + + +

+ + + Date/Time Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + age + + age ( timestamp, timestamp ) + interval + + + Subtract arguments, producing a symbolic result that + uses years and months, rather than just days + + + age(timestamp '2001-04-10', timestamp '1957-06-13') + 43 years 9 mons 27 days + + + + + + age ( timestamp ) + interval + + + Subtract argument from current_date (at midnight) + + + age(timestamp '1957-06-13') + 62 years 6 mons 10 days + + + + + + + clock_timestamp + + clock_timestamp ( ) + timestamp with time zone + + + Current date and time (changes during statement execution); + see + + + clock_timestamp() + 2019-12-23 14:39:53.662522-05 + + + + + + + current_date + + current_date + date + + + Current date; see + + + current_date + 2019-12-23 + + + + + + + current_time + + current_time + time with time zone + + + Current time of day; see + + + current_time + 14:39:53.662522-05 + + + + + + current_time ( integer ) + time with time zone + + + Current time of day, with limited precision; + see + + + current_time(2) + 14:39:53.66-05 + + + + + + + current_timestamp + + current_timestamp + timestamp with time zone + + + Current date and time (start of current transaction); + see + + + current_timestamp + 2019-12-23 14:39:53.662522-05 + + + + + + current_timestamp ( integer ) + timestamp with time zone + + + Current date and time (start of current transaction), with limited precision; + see + + + current_timestamp(0) + 2019-12-23 14:39:53-05 + + + + + + + date_add + + date_add ( timestamp with time zone, interval , text ) + timestamp with time zone + + + Add an interval to a timestamp with time + zone, computing times of day and daylight-savings adjustments + according to the time zone named by the third argument, or the + current setting if that is omitted. + The form with two arguments is equivalent to the timestamp with + time zone + interval operator. + + + date_add('2021-10-31 00:00:00+02'::timestamptz, '1 day'::interval, 'Europe/Warsaw') + 2021-10-31 23:00:00+00 + + + + + + date_bin ( interval, timestamp, timestamp ) + timestamp + + + Bin input into specified interval aligned with specified origin; see + + + date_bin('15 minutes', timestamp '2001-02-16 20:38:40', timestamp '2001-02-16 20:05:00') + 2001-02-16 20:35:00 + + + + + + + date_part + + date_part ( text, timestamp ) + double precision + + + Get timestamp subfield (equivalent to extract); + see + + + date_part('hour', timestamp '2001-02-16 20:38:40') + 20 + + + + + + date_part ( text, interval ) + double precision + + + Get interval subfield (equivalent to extract); + see + + + date_part('month', interval '2 years 3 months') + 3 + + + + + + + date_subtract + + date_subtract ( timestamp with time zone, interval , text ) + timestamp with time zone + + + Subtract an interval from a timestamp with time + zone, computing times of day and daylight-savings adjustments + according to the time zone named by the third argument, or the + current setting if that is omitted. + The form with two arguments is equivalent to the timestamp with + time zone - interval operator. + + + date_subtract('2021-11-01 00:00:00+01'::timestamptz, '1 day'::interval, 'Europe/Warsaw') + 2021-10-30 22:00:00+00 + + + + + + + date_trunc + + date_trunc ( text, timestamp ) + timestamp + + + Truncate to specified precision; see + + + date_trunc('hour', timestamp '2001-02-16 20:38:40') + 2001-02-16 20:00:00 + + + + + + date_trunc ( text, timestamp with time zone, text ) + timestamp with time zone + + + Truncate to specified precision in the specified time zone; see + + + + date_trunc('day', timestamptz '2001-02-16 20:38:40+00', 'Australia/Sydney') + 2001-02-16 13:00:00+00 + + + + + + date_trunc ( text, interval ) + interval + + + Truncate to specified precision; see + + + + date_trunc('hour', interval '2 days 3 hours 40 minutes') + 2 days 03:00:00 + + + + + + + extract + + extract ( field from timestamp ) + numeric + + + Get timestamp subfield; see + + + extract(hour from timestamp '2001-02-16 20:38:40') + 20 + + + + + + extract ( field from interval ) + numeric + + + Get interval subfield; see + + + extract(month from interval '2 years 3 months') + 3 + + + + + + + isfinite + + isfinite ( date ) + boolean + + + Test for finite date (not +/-infinity) + + + isfinite(date '2001-02-16') + true + + + + + + isfinite ( timestamp ) + boolean + + + Test for finite timestamp (not +/-infinity) + + + isfinite(timestamp 'infinity') + false + + + + + + isfinite ( interval ) + boolean + + + Test for finite interval (not +/-infinity) + + + isfinite(interval '4 hours') + true + + + + + + + justify_days + + justify_days ( interval ) + interval + + + Adjust interval, converting 30-day time periods to months + + + justify_days(interval '1 year 65 days') + 1 year 2 mons 5 days + + + + + + + justify_hours + + justify_hours ( interval ) + interval + + + Adjust interval, converting 24-hour time periods to days + + + justify_hours(interval '50 hours 10 minutes') + 2 days 02:10:00 + + + + + + + justify_interval + + justify_interval ( interval ) + interval + + + Adjust interval using justify_days + and justify_hours, with additional sign + adjustments + + + justify_interval(interval '1 mon -1 hour') + 29 days 23:00:00 + + + + + + + localtime + + localtime + time + + + Current time of day; + see + + + localtime + 14:39:53.662522 + + + + + + localtime ( integer ) + time + + + Current time of day, with limited precision; + see + + + localtime(0) + 14:39:53 + + + + + + + localtimestamp + + localtimestamp + timestamp + + + Current date and time (start of current transaction); + see + + + localtimestamp + 2019-12-23 14:39:53.662522 + + + + + + localtimestamp ( integer ) + timestamp + + + Current date and time (start of current + transaction), with limited precision; + see + + + localtimestamp(2) + 2019-12-23 14:39:53.66 + + + + + + + make_date + + make_date ( year int, + month int, + day int ) + date + + + Create date from year, month and day fields + (negative years signify BC) + + + make_date(2013, 7, 15) + 2013-07-15 + + + + + + make_interval + + make_interval ( years int + , months int + , weeks int + , days int + , hours int + , mins int + , secs double precision + ) + interval + + + Create interval from years, months, weeks, days, hours, minutes and + seconds fields, each of which can default to zero + + + make_interval(days => 10) + 10 days + + + + + + + make_time + + make_time ( hour int, + min int, + sec double precision ) + time + + + Create time from hour, minute and seconds fields + + + make_time(8, 15, 23.5) + 08:15:23.5 + + + + + + + make_timestamp + + make_timestamp ( year int, + month int, + day int, + hour int, + min int, + sec double precision ) + timestamp + + + Create timestamp from year, month, day, hour, minute and seconds fields + (negative years signify BC) + + + make_timestamp(2013, 7, 15, 8, 15, 23.5) + 2013-07-15 08:15:23.5 + + + + + + + make_timestamptz + + make_timestamptz ( year int, + month int, + day int, + hour int, + min int, + sec double precision + , timezone text ) + timestamp with time zone + + + Create timestamp with time zone from year, month, day, hour, minute + and seconds fields (negative years signify BC). + If timezone is not + specified, the current time zone is used; the examples assume the + session time zone is Europe/London + + + make_timestamptz(2013, 7, 15, 8, 15, 23.5) + 2013-07-15 08:15:23.5+01 + + + make_timestamptz(2013, 7, 15, 8, 15, 23.5, 'America/New_York') + 2013-07-15 13:15:23.5+01 + + + + + + + now + + now ( ) + timestamp with time zone + + + Current date and time (start of current transaction); + see + + + now() + 2019-12-23 14:39:53.662522-05 + + + + + + + statement_timestamp + + statement_timestamp ( ) + timestamp with time zone + + + Current date and time (start of current statement); + see + + + statement_timestamp() + 2019-12-23 14:39:53.662522-05 + + + + + + + timeofday + + timeofday ( ) + text + + + Current date and time + (like clock_timestamp, but as a text string); + see + + + timeofday() + Mon Dec 23 14:39:53.662522 2019 EST + + + + + + + transaction_timestamp + + transaction_timestamp ( ) + timestamp with time zone + + + Current date and time (start of current transaction); + see + + + transaction_timestamp() + 2019-12-23 14:39:53.662522-05 + + + + + + + to_timestamp + + to_timestamp ( double precision ) + timestamp with time zone + + + Convert Unix epoch (seconds since 1970-01-01 00:00:00+00) to + timestamp with time zone + + + to_timestamp(1284352323) + 2010-09-13 04:32:03+00 + + + + +

+ + + + OVERLAPS + + In addition to these functions, the SQL OVERLAPS operator is + supported: + +(start1, end1) OVERLAPS (start2, end2) +(start1, length1) OVERLAPS (start2, length2) + + This expression yields true when two time periods (defined by their + endpoints) overlap, false when they do not overlap. The endpoints + can be specified as pairs of dates, times, or time stamps; or as + a date, time, or time stamp followed by an interval. When a pair + of values is provided, either the start or the end can be written + first; OVERLAPS automatically takes the earlier value + of the pair as the start. Each time period is considered to + represent the half-open interval start <= + time < end, unless + start and end are equal in which case it + represents that single time instant. This means for instance that two + time periods with only an endpoint in common do not overlap. + + + +SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS + (DATE '2001-10-30', DATE '2002-10-30'); +Result: true +SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS + (DATE '2001-10-30', DATE '2002-10-30'); +Result: false +SELECT (DATE '2001-10-29', DATE '2001-10-30') OVERLAPS + (DATE '2001-10-30', DATE '2001-10-31'); +Result: false +SELECT (DATE '2001-10-30', DATE '2001-10-30') OVERLAPS + (DATE '2001-10-30', DATE '2001-10-31'); +Result: true + + + + When adding an interval value to (or subtracting an + interval value from) a timestamp + or timestamp with time zone value, the months, days, and + microseconds fields of the interval value are handled in turn. + First, a nonzero months field advances or decrements the date of the + timestamp by the indicated number of months, keeping the day of month the + same unless it would be past the end of the new month, in which case the + last day of that month is used. (For example, March 31 plus 1 month + becomes April 30, but March 31 plus 2 months becomes May 31.) + Then the days field advances or decrements the date of the timestamp by + the indicated number of days. In both these steps the local time of day + is kept the same. Finally, if there is a nonzero microseconds field, it + is added or subtracted literally. + When doing arithmetic on a timestamp with time zone value in + a time zone that recognizes DST, this means that adding or subtracting + (say) interval '1 day' does not necessarily have the + same result as adding or subtracting interval '24 + hours'. + For example, with the session time zone set + to America/Denver: + +SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '1 day'; +Result: 2005-04-03 12:00:00-06 +SELECT timestamp with time zone '2005-04-02 12:00:00-07' + interval '24 hours'; +Result: 2005-04-03 13:00:00-06 + + This happens because an hour was skipped due to a change in daylight saving + time at 2005-04-03 02:00:00 in time zone + America/Denver. + + + + Note there can be ambiguity in the months field returned by + age because different months have different numbers of + days. PostgreSQL's approach uses the month from the + earlier of the two dates when calculating partial months. For example, + age('2004-06-01', '2004-04-30') uses April to yield + 1 mon 1 day, while using May would yield 1 mon 2 + days because May has 31 days, while April has only 30. + + + + Subtraction of dates and timestamps can also be complex. One conceptually + simple way to perform subtraction is to convert each value to a number + of seconds using EXTRACT(EPOCH FROM ...), then subtract the + results; this produces the + number of seconds between the two values. This will adjust + for the number of days in each month, timezone changes, and daylight + saving time adjustments. Subtraction of date or timestamp + values with the - operator + returns the number of days (24-hours) and hours/minutes/seconds + between the values, making the same adjustments. The age + function returns years, months, days, and hours/minutes/seconds, + performing field-by-field subtraction and then adjusting for negative + field values. The following queries illustrate the differences in these + approaches. The sample results were produced with timezone + = 'US/Eastern'; there is a daylight saving time change between the + two dates used: + + + +SELECT EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') - + EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00'); +Result: 10537200.000000 +SELECT (EXTRACT(EPOCH FROM timestamptz '2013-07-01 12:00:00') - + EXTRACT(EPOCH FROM timestamptz '2013-03-01 12:00:00')) + / 60 / 60 / 24; +Result: 121.9583333333333333 +SELECT timestamptz '2013-07-01 12:00:00' - timestamptz '2013-03-01 12:00:00'; +Result: 121 days 23:00:00 +SELECT age(timestamptz '2013-07-01 12:00:00', timestamptz '2013-03-01 12:00:00'); +Result: 4 mons + + + + <function>EXTRACT</function>, <function>date_part</function> + + + date_part + + + extract + + + +EXTRACT(field FROM source) + + + + The extract function retrieves subfields + such as year or hour from date/time values. + source must be a value expression of + type timestamp, date, time, + or interval. (Timestamps and times can be with or + without time zone.) + field is an identifier or + string that selects what field to extract from the source value. + Not all fields are valid for every input data type; for example, fields + smaller than a day cannot be extracted from a date, while + fields of a day or more cannot be extracted from a time. + The extract function returns values of type + numeric. + + + + The following are valid field names: + + + + + century + + + The century; for interval values, the year field + divided by 100 + + + +SELECT EXTRACT(CENTURY FROM TIMESTAMP '2000-12-16 12:21:13'); +Result: 20 +SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 21 +SELECT EXTRACT(CENTURY FROM DATE '0001-01-01 AD'); +Result: 1 +SELECT EXTRACT(CENTURY FROM DATE '0001-12-31 BC'); +Result: -1 +SELECT EXTRACT(CENTURY FROM INTERVAL '2001 years'); +Result: 20 + + + + + + day + + + The day of the month (1–31); for interval + values, the number of days + + + +SELECT EXTRACT(DAY FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 16 +SELECT EXTRACT(DAY FROM INTERVAL '40 days 1 minute'); +Result: 40 + + + + + + + decade + + + The year field divided by 10 + + + +SELECT EXTRACT(DECADE FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 200 + + + + + + dow + + + The day of the week as Sunday (0) to + Saturday (6) + + + +SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 5 + + + Note that extract's day of the week numbering + differs from that of the to_char(..., + 'D') function. + + + + + + + doy + + + The day of the year (1–365/366) + + + +SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 47 + + + + + + epoch + + + For timestamp with time zone values, the + number of seconds since 1970-01-01 00:00:00 UTC (negative for + timestamps before that); + for date and timestamp values, the + nominal number of seconds since 1970-01-01 00:00:00, + without regard to timezone or daylight-savings rules; + for interval values, the total number + of seconds in the interval + + + +SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40.12-08'); +Result: 982384720.120000 +SELECT EXTRACT(EPOCH FROM TIMESTAMP '2001-02-16 20:38:40.12'); +Result: 982355920.120000 +SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours'); +Result: 442800.000000 + + + + You can convert an epoch value back to a timestamp with time zone + with to_timestamp: + + +SELECT to_timestamp(982384720.12); +Result: 2001-02-17 04:38:40.12+00 + + + + Beware that applying to_timestamp to an epoch + extracted from a date or timestamp value + could produce a misleading result: the result will effectively + assume that the original value had been given in UTC, which might + not be the case. + + + + + + hour + + + The hour field (0–23 in timestamps, unrestricted in + intervals) + + + +SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 20 + + + + + + isodow + + + The day of the week as Monday (1) to + Sunday (7) + + + +SELECT EXTRACT(ISODOW FROM TIMESTAMP '2001-02-18 20:38:40'); +Result: 7 + + + This is identical to dow except for Sunday. This + matches the ISO 8601 day of the week numbering. + + + + + + + isoyear + + + The ISO 8601 week-numbering year that the date + falls in + + + +SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-01'); +Result: 2005 +SELECT EXTRACT(ISOYEAR FROM DATE '2006-01-02'); +Result: 2006 + + + + Each ISO 8601 week-numbering year begins with the + Monday of the week containing the 4th of January, so in early + January or late December the ISO year may be + different from the Gregorian year. See the week + field for more information. + + + + + + julian + + + The Julian Date corresponding to the + date or timestamp. Timestamps + that are not local midnight result in a fractional value. See + for more information. + + + +SELECT EXTRACT(JULIAN FROM DATE '2006-01-01'); +Result: 2453737 +SELECT EXTRACT(JULIAN FROM TIMESTAMP '2006-01-01 12:00'); +Result: 2453737.50000000000000000000 + + + + + + microseconds + + + The seconds field, including fractional parts, multiplied by 1 + 000 000; note that this includes full seconds + + + +SELECT EXTRACT(MICROSECONDS FROM TIME '17:12:28.5'); +Result: 28500000 + + + + + + millennium + + + The millennium; for interval values, the year field + divided by 1000 + + + +SELECT EXTRACT(MILLENNIUM FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 3 +SELECT EXTRACT(MILLENNIUM FROM INTERVAL '2001 years'); +Result: 2 + + + + Years in the 1900s are in the second millennium. + The third millennium started January 1, 2001. + + + + + + milliseconds + + + The seconds field, including fractional parts, multiplied by + 1000. Note that this includes full seconds. + + + +SELECT EXTRACT(MILLISECONDS FROM TIME '17:12:28.5'); +Result: 28500.000 + + + + + + minute + + + The minutes field (0–59) + + + +SELECT EXTRACT(MINUTE FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 38 + + + + + + month + + + The number of the month within the year (1–12); + for interval values, the number of months modulo 12 + (0–11) + + + +SELECT EXTRACT(MONTH FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 2 +SELECT EXTRACT(MONTH FROM INTERVAL '2 years 3 months'); +Result: 3 +SELECT EXTRACT(MONTH FROM INTERVAL '2 years 13 months'); +Result: 1 + + + + + + quarter + + + The quarter of the year (1–4) that the date is in; + for interval values, the month field divided by 3 + plus 1 + + + +SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 1 +SELECT EXTRACT(QUARTER FROM INTERVAL '1 year 6 months'); +Result: 3 + + + + + + second + + + The seconds field, including any fractional seconds + + + +SELECT EXTRACT(SECOND FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 40.000000 +SELECT EXTRACT(SECOND FROM TIME '17:12:28.5'); +Result: 28.500000 + + + + + timezone + + + The time zone offset from UTC, measured in seconds. Positive values + correspond to time zones east of UTC, negative values to + zones west of UTC. (Technically, + PostgreSQL does not use UTC because + leap seconds are not handled.) + + + + + + timezone_hour + + + The hour component of the time zone offset + + + + + + timezone_minute + + + The minute component of the time zone offset + + + + + + week + + + The number of the ISO 8601 week-numbering week of + the year. By definition, ISO weeks start on Mondays and the first + week of a year contains January 4 of that year. In other words, the + first Thursday of a year is in week 1 of that year. + + + In the ISO week-numbering system, it is possible for early-January + dates to be part of the 52nd or 53rd week of the previous year, and for + late-December dates to be part of the first week of the next year. + For example, 2005-01-01 is part of the 53rd week of year + 2004, and 2006-01-01 is part of the 52nd week of year + 2005, while 2012-12-31 is part of the first week of 2013. + It's recommended to use the isoyear field together with + week to get consistent results. + + + + For interval values, the week field is simply the number + of integral days divided by 7. + + + +SELECT EXTRACT(WEEK FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 7 +SELECT EXTRACT(WEEK FROM INTERVAL '13 days 24 hours'); +Result: 1 + + + + + + year + + + The year field. Keep in mind there is no 0 AD, so subtracting + BC years from AD years should be done with care. + + + +SELECT EXTRACT(YEAR FROM TIMESTAMP '2001-02-16 20:38:40'); +Result: 2001 + + + + + + + + + When processing an interval value, + the extract function produces field values that + match the interpretation used by the interval output function. This + can produce surprising results if one starts with a non-normalized + interval representation, for example: + +SELECT INTERVAL '80 minutes'; +Result: 01:20:00 +SELECT EXTRACT(MINUTES FROM INTERVAL '80 minutes'); +Result: 20 + + + + + + When the input value is +/-Infinity, extract returns + +/-Infinity for monotonically-increasing fields (epoch, + julian, year, isoyear, + decade, century, and millennium + for timestamp inputs; epoch, hour, + day, year, decade, + century, and millennium for + interval inputs). + For other fields, NULL is returned. PostgreSQL + versions before 9.6 returned zero for all cases of infinite input. + + + + + The extract function is primarily intended + for computational processing. For formatting date/time values for + display, see . + + + + The date_part function is modeled on the traditional + Ingres equivalent to the + SQL-standard function extract: + +date_part('field', source) + + Note that here the field parameter needs to + be a string value, not a name. The valid field names for + date_part are the same as for + extract. + For historical reasons, the date_part function + returns values of type double precision. This can result in + a loss of precision in certain uses. Using extract + is recommended instead. + + + +SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40'); +Result: 16 +SELECT date_part('hour', INTERVAL '4 hours 3 minutes'); +Result: 4 + + + + + + <function>date_trunc</function> + + + date_trunc + + + + The function date_trunc is conceptually + similar to the trunc function for numbers. + + + + +date_trunc(field, source , time_zone ) + + source is a value expression of type + timestamp, timestamp with time zone, + or interval. + (Values of type date and + time are cast automatically to timestamp or + interval, respectively.) + field selects to which precision to + truncate the input value. The return value is likewise of type + timestamp, timestamp with time zone, + or interval, + and it has all fields that are less significant than the + selected one set to zero (or one, for day and month). + + + + Valid values for field are: + + microseconds + milliseconds + second + minute + hour + day + week + month + quarter + year + decade + century + millennium + + + + + When the input value is of type timestamp with time zone, + the truncation is performed with respect to a particular time zone; + for example, truncation to day produces a value that + is midnight in that zone. By default, truncation is done with respect + to the current setting, but the + optional time_zone argument can be provided + to specify a different time zone. The time zone name can be specified + in any of the ways described in . + + + + A time zone cannot be specified when processing timestamp without + time zone or interval inputs. These are always + taken at face value. + + + + Examples (assuming the local time zone is America/New_York): + +SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40'); +Result: 2001-02-16 20:00:00 +SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40'); +Result: 2001-01-01 00:00:00 +SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00'); +Result: 2001-02-16 00:00:00-05 +SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00', 'Australia/Sydney'); +Result: 2001-02-16 08:00:00-05 +SELECT date_trunc('hour', INTERVAL '3 days 02:47:33'); +Result: 3 days 02:00:00 + + + + + + <function>date_bin</function> + + + date_bin + + + + The function date_bin bins the input + timestamp into the specified interval (the stride) + aligned with a specified origin. + + + + +date_bin(stride, source, origin) + + source is a value expression of type + timestamp or timestamp with time zone. (Values + of type date are cast automatically to + timestamp.) stride is a value + expression of type interval. The return value is likewise + of type timestamp or timestamp with time zone, + and it marks the beginning of the bin into which the + source is placed. + + + + Examples: + +SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01'); +Result: 2020-02-11 15:30:00 +SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-01-01 00:02:30'); +Result: 2020-02-11 15:32:30 + + + + + In the case of full units (1 minute, 1 hour, etc.), it gives the same result as + the analogous date_trunc call, but the difference is + that date_bin can truncate to an arbitrary interval. + + + + The stride interval must be greater than zero and + cannot contain units of month or larger. + + + + + <literal>AT TIME ZONE</literal> and <literal>AT LOCAL</literal> + + + time zone + conversion + + + + AT TIME ZONE + + + + AT LOCAL + + + + The AT TIME ZONE operator converts time + stamp without time zone to/from + time stamp with time zone, and + time with time zone values to different time + zones. shows its + variants. + + + + <literal>AT TIME ZONE</literal> and <literal>AT LOCAL</literal> Variants + + + + + Operator + + + Description + + + Example(s) + + + + + + + + timestamp without time zone AT TIME ZONE zone + timestamp with time zone + + + Converts given time stamp without time zone to + time stamp with time zone, assuming the given + value is in the named time zone. + + + timestamp '2001-02-16 20:38:40' at time zone 'America/Denver' + 2001-02-17 03:38:40+00 + + + + + + timestamp without time zone AT LOCAL + timestamp with time zone + + + Converts given time stamp without time zone to + time stamp with the session's + TimeZone value as time zone. + + + timestamp '2001-02-16 20:38:40' at local + 2001-02-17 03:38:40+00 + + + + + + timestamp with time zone AT TIME ZONE zone + timestamp without time zone + + + Converts given time stamp with time zone to + time stamp without time zone, as the time would + appear in that zone. + + + timestamp with time zone '2001-02-16 20:38:40-05' at time zone 'America/Denver' + 2001-02-16 18:38:40 + + + + + + timestamp with time zone AT LOCAL + timestamp without time zone + + + Converts given time stamp with time zone to + time stamp without time zone, as the time would + appear with the session's TimeZone value as time zone. + + + timestamp with time zone '2001-02-16 20:38:40-05' at local + 2001-02-16 18:38:40 + + + + + + time with time zone AT TIME ZONE zone + time with time zone + + + Converts given time with time zone to a new time + zone. Since no date is supplied, this uses the currently active UTC + offset for the named destination zone. + + + time with time zone '05:34:17-05' at time zone 'UTC' + 10:34:17+00 + + + + + + time with time zone AT LOCAL + time with time zone + + + Converts given time with time zone to a new time + zone. Since no date is supplied, this uses the currently active UTC + offset for the session's TimeZone value. + + + Assuming the session's TimeZone is set to UTC: + + + time with time zone '05:34:17-05' at local + 10:34:17+00 + + + + +

+ + + In these expressions, the desired time zone zone can be + specified either as a text value (e.g., 'America/Los_Angeles') + or as an interval (e.g., INTERVAL '-08:00'). + In the text case, a time zone name can be specified in any of the ways + described in . + The interval case is only useful for zones that have fixed offsets from + UTC, so it is not very common in practice. + + + + The syntax AT LOCAL may be used as shorthand for + AT TIME ZONE local, where + local is the session's + TimeZone value. + + + + Examples (assuming the current setting + is America/Los_Angeles): + +SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'America/Denver'; +Result: 2001-02-16 19:38:40-08 +SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'America/Denver'; +Result: 2001-02-16 18:38:40 +SELECT TIMESTAMP '2001-02-16 20:38:40' AT TIME ZONE 'Asia/Tokyo' AT TIME ZONE 'America/Chicago'; +Result: 2001-02-16 05:38:40 +SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT LOCAL; +Result: 2001-02-16 17:38:40 +SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE '+05'; +Result: 2001-02-16 20:38:40 +SELECT TIME WITH TIME ZONE '20:38:40-05' AT LOCAL; +Result: 17:38:40 + + The first example adds a time zone to a value that lacks it, and + displays the value using the current TimeZone + setting. The second example shifts the time stamp with time zone value + to the specified time zone, and returns the value without a time zone. + This allows storage and display of values different from the current + TimeZone setting. The third example converts + Tokyo time to Chicago time. The fourth example shifts the time stamp + with time zone value to the time zone currently specified by the + TimeZone setting and returns the value without a + time zone. The fifth example demonstrates that the sign in a POSIX-style + time zone specification has the opposite meaning of the sign in an + ISO-8601 datetime literal, as described in + and . + + + + The sixth example is a cautionary tale. Due to the fact that there is no + date associated with the input value, the conversion is made using the + current date of the session. Therefore, this static example may show a wrong + result depending on the time of the year it is viewed because + 'America/Los_Angeles' observes Daylight Savings Time. + + + + The function timezone(zone, + timestamp) is equivalent to the SQL-conforming construct + timestamp AT TIME ZONE + zone. + + + + The function timezone(zone, + time) is equivalent to the SQL-conforming construct + time AT TIME ZONE + zone. + + + + The function timezone(timestamp) + is equivalent to the SQL-conforming construct timestamp + AT LOCAL. + + + + The function timezone(time) + is equivalent to the SQL-conforming construct time + AT LOCAL. + + + + + Current Date/Time + + + date + current + + + + time + current + + + + PostgreSQL provides a number of functions + that return values related to the current date and time. These + SQL-standard functions all return values based on the start time of + the current transaction: + +CURRENT_DATE +CURRENT_TIME +CURRENT_TIMESTAMP +CURRENT_TIME(precision) +CURRENT_TIMESTAMP(precision) +LOCALTIME +LOCALTIMESTAMP +LOCALTIME(precision) +LOCALTIMESTAMP(precision) + + + + + CURRENT_TIME and + CURRENT_TIMESTAMP deliver values with time zone; + LOCALTIME and + LOCALTIMESTAMP deliver values without time zone. + + + + CURRENT_TIME, + CURRENT_TIMESTAMP, + LOCALTIME, and + LOCALTIMESTAMP + can optionally take + a precision parameter, which causes the result to be rounded + to that many fractional digits in the seconds field. Without a precision parameter, + the result is given to the full available precision. + + + + Some examples: + +SELECT CURRENT_TIME; +Result: 14:39:53.662522-05 +SELECT CURRENT_DATE; +Result: 2019-12-23 +SELECT CURRENT_TIMESTAMP; +Result: 2019-12-23 14:39:53.662522-05 +SELECT CURRENT_TIMESTAMP(2); +Result: 2019-12-23 14:39:53.66-05 +SELECT LOCALTIMESTAMP; +Result: 2019-12-23 14:39:53.662522 + + + + + Since these functions return + the start time of the current transaction, their values do not + change during the transaction. This is considered a feature: + the intent is to allow a single transaction to have a consistent + notion of the current time, so that multiple + modifications within the same transaction bear the same + time stamp. + + + + + Other database systems might advance these values more + frequently. + + + + + PostgreSQL also provides functions that + return the start time of the current statement, as well as the actual + current time at the instant the function is called. The complete list + of non-SQL-standard time functions is: + +transaction_timestamp() +statement_timestamp() +clock_timestamp() +timeofday() +now() + + + + + transaction_timestamp() is equivalent to + CURRENT_TIMESTAMP, but is named to clearly reflect + what it returns. + statement_timestamp() returns the start time of the current + statement (more specifically, the time of receipt of the latest command + message from the client). + statement_timestamp() and transaction_timestamp() + return the same value during the first statement of a transaction, but might + differ during subsequent statements. + clock_timestamp() returns the actual current time, and + therefore its value changes even within a single SQL statement. + timeofday() is a historical + PostgreSQL function. Like + clock_timestamp(), it returns the actual current time, + but as a formatted text string rather than a timestamp + with time zone value. + now() is a traditional PostgreSQL + equivalent to transaction_timestamp(). + + + + All the date/time data types also accept the special literal value + now to specify the current date and time (again, + interpreted as the transaction start time). Thus, + the following three all return the same result: + +SELECT CURRENT_TIMESTAMP; +SELECT now(); +SELECT TIMESTAMP 'now'; -- but see tip below + + + + + + Do not use the third form when specifying a value to be evaluated later, + for example in a DEFAULT clause for a table column. + The system will convert now + to a timestamp as soon as the constant is parsed, so that when + the default value is needed, + the time of the table creation would be used! The first two + forms will not be evaluated until the default value is used, + because they are function calls. Thus they will give the desired + behavior of defaulting to the time of row insertion. + (See also .) + + + + + + Delaying Execution + + + pg_sleep + + + pg_sleep_for + + + pg_sleep_until + + + sleep + + + delay + + + + The following functions are available to delay execution of the server + process: + +pg_sleep ( double precision ) +pg_sleep_for ( interval ) +pg_sleep_until ( timestamp with time zone ) + + + pg_sleep makes the current session's process + sleep until the given number of seconds have + elapsed. Fractional-second delays can be specified. + pg_sleep_for is a convenience function to + allow the sleep time to be specified as an interval. + pg_sleep_until is a convenience function for when + a specific wake-up time is desired. + For example: + + +SELECT pg_sleep(1.5); +SELECT pg_sleep_for('5 minutes'); +SELECT pg_sleep_until('tomorrow 03:00'); + + + + + + The effective resolution of the sleep interval is platform-specific; + 0.01 seconds is a common value. The sleep delay will be at least as long + as specified. It might be longer depending on factors such as server load. + In particular, pg_sleep_until is not guaranteed to + wake up exactly at the specified time, but it will not wake up any earlier. + + + + + + Make sure that your session does not hold more locks than necessary + when calling pg_sleep or its variants. Otherwise + other sessions might have to wait for your sleeping process, slowing down + the entire system. + + + + + diff --git a/doc/src/sgml/func/func-enum.sgml b/doc/src/sgml/func/func-enum.sgml new file mode 100644 index 00000000000..6227afe4057 --- /dev/null +++ b/doc/src/sgml/func/func-enum.sgml @@ -0,0 +1,121 @@ + + Enum Support Functions + + + For enum types (described in ), + there are several functions that allow cleaner programming without + hard-coding particular values of an enum type. + These are listed in . The examples + assume an enum type created as: + + +CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple'); + + + + + + Enum Support Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + enum_first + + enum_first ( anyenum ) + anyenum + + + Returns the first value of the input enum type. + + + enum_first(null::rainbow) + red + + + + + + enum_last + + enum_last ( anyenum ) + anyenum + + + Returns the last value of the input enum type. + + + enum_last(null::rainbow) + purple + + + + + + enum_range + + enum_range ( anyenum ) + anyarray + + + Returns all values of the input enum type in an ordered array. + + + enum_range(null::rainbow) + {red,orange,yellow,&zwsp;green,blue,purple} + + + + + enum_range ( anyenum, anyenum ) + anyarray + + + Returns the range between the two given enum values, as an ordered + array. The values must be from the same enum type. If the first + parameter is null, the result will start with the first value of + the enum type. + If the second parameter is null, the result will end with the last + value of the enum type. + + + enum_range('orange'::rainbow, 'green'::rainbow) + {orange,yellow,green} + + + enum_range(NULL, 'green'::rainbow) + {red,orange,&zwsp;yellow,green} + + + enum_range('orange'::rainbow, NULL) + {orange,yellow,green,&zwsp;blue,purple} + + + + +

+ + + Notice that except for the two-argument form of enum_range, + these functions disregard the specific value passed to them; they care + only about its declared data type. Either null or a specific value of + the type can be passed, with the same result. It is more common to + apply these functions to a table column or function argument than to + a hardwired type name as used in the examples. + + diff --git a/doc/src/sgml/func/func-event-triggers.sgml b/doc/src/sgml/func/func-event-triggers.sgml new file mode 100644 index 00000000000..9f3f51e9f51 --- /dev/null +++ b/doc/src/sgml/func/func-event-triggers.sgml @@ -0,0 +1,332 @@ + + Event Trigger Functions + + + PostgreSQL provides these helper functions + to retrieve information from event triggers. + + + + For more information about event triggers, + see . + + + + Capturing Changes at Command End + + + pg_event_trigger_ddl_commands + + + +pg_event_trigger_ddl_commands () setof record + + + + pg_event_trigger_ddl_commands returns a list of + DDL commands executed by each user action, + when invoked in a function attached to a + ddl_command_end event trigger. If called in any other + context, an error is raised. + pg_event_trigger_ddl_commands returns one row for each + base command executed; some commands that are a single SQL sentence + may return more than one row. This function returns the following + columns: + + + + + + Name + Type + Description + + + + + + classid + oid + OID of catalog the object belongs in + + + objid + oid + OID of the object itself + + + objsubid + integer + Sub-object ID (e.g., attribute number for a column) + + + command_tag + text + Command tag + + + object_type + text + Type of the object + + + schema_name + text + + Name of the schema the object belongs in, if any; otherwise NULL. + No quoting is applied. + + + + object_identity + text + + Text rendering of the object identity, schema-qualified. Each + identifier included in the identity is quoted if necessary. + + + + in_extension + boolean + True if the command is part of an extension script + + + command + pg_ddl_command + + A complete representation of the command, in internal format. + This cannot be output directly, but it can be passed to other + functions to obtain different pieces of information about the + command. + + + + + + + + + + Processing Objects Dropped by a DDL Command + + + pg_event_trigger_dropped_objects + + + +pg_event_trigger_dropped_objects () setof record + + + + pg_event_trigger_dropped_objects returns a list of all objects + dropped by the command in whose sql_drop event it is called. + If called in any other context, an error is raised. + This function returns the following columns: + + + + + + Name + Type + Description + + + + + + classid + oid + OID of catalog the object belonged in + + + objid + oid + OID of the object itself + + + objsubid + integer + Sub-object ID (e.g., attribute number for a column) + + + original + boolean + True if this was one of the root object(s) of the deletion + + + normal + boolean + + True if there was a normal dependency relationship + in the dependency graph leading to this object + + + + is_temporary + boolean + + True if this was a temporary object + + + + object_type + text + Type of the object + + + schema_name + text + + Name of the schema the object belonged in, if any; otherwise NULL. + No quoting is applied. + + + + object_name + text + + Name of the object, if the combination of schema and name can be + used as a unique identifier for the object; otherwise NULL. + No quoting is applied, and name is never schema-qualified. + + + + object_identity + text + + Text rendering of the object identity, schema-qualified. Each + identifier included in the identity is quoted if necessary. + + + + address_names + text[] + + An array that, together with object_type and + address_args, can be used by + the pg_get_object_address function to + recreate the object address in a remote server containing an + identically named object of the same kind. + + + + address_args + text[] + + Complement for address_names + + + + + + + + + The pg_event_trigger_dropped_objects function can be used + in an event trigger like this: + +CREATE FUNCTION test_event_trigger_for_drops() + RETURNS event_trigger LANGUAGE plpgsql AS $$ +DECLARE + obj record; +BEGIN + FOR obj IN SELECT * FROM pg_event_trigger_dropped_objects() + LOOP + RAISE NOTICE '% dropped object: % %.% %', + tg_tag, + obj.object_type, + obj.schema_name, + obj.object_name, + obj.object_identity; + END LOOP; +END; +$$; +CREATE EVENT TRIGGER test_event_trigger_for_drops + ON sql_drop + EXECUTE FUNCTION test_event_trigger_for_drops(); + + + + + + Handling a Table Rewrite Event + + + The functions shown in + + provide information about a table for which a + table_rewrite event has just been called. + If called in any other context, an error is raised. + + + + Table Rewrite Information Functions + + + + + Function + + + Description + + + + + + + + + pg_event_trigger_table_rewrite_oid + + pg_event_trigger_table_rewrite_oid () + oid + + + Returns the OID of the table about to be rewritten. + + + + + + + pg_event_trigger_table_rewrite_reason + + pg_event_trigger_table_rewrite_reason () + integer + + + Returns a code explaining the reason(s) for rewriting. The value is + a bitmap built from the following values: 1 + (the table has changed its persistence), 2 + (default value of a column has changed), 4 + (a column has a new data type) and 8 + (the table access method has changed). + + + + +

+ + + These functions can be used in an event trigger like this: + +CREATE FUNCTION test_event_trigger_table_rewrite_oid() + RETURNS event_trigger + LANGUAGE plpgsql AS +$$ +BEGIN + RAISE NOTICE 'rewriting table % for reason %', + pg_event_trigger_table_rewrite_oid()::regclass, + pg_event_trigger_table_rewrite_reason(); +END; +$$; + +CREATE EVENT TRIGGER test_table_rewrite_oid + ON table_rewrite + EXECUTE FUNCTION test_event_trigger_table_rewrite_oid(); + + + + diff --git a/doc/src/sgml/func/func-formatting.sgml b/doc/src/sgml/func/func-formatting.sgml new file mode 100644 index 00000000000..806302b2f7b --- /dev/null +++ b/doc/src/sgml/func/func-formatting.sgml @@ -0,0 +1,1193 @@ + + Data Type Formatting Functions + + + formatting + + + + The PostgreSQL formatting functions + provide a powerful set of tools for converting various data types + (date/time, integer, floating point, numeric) to formatted strings + and for converting from formatted strings to specific data types. + lists them. + These functions all follow a common calling convention: the first + argument is the value to be formatted and the second argument is a + template that defines the output or input format. + + + + Formatting Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + to_char + + to_char ( timestamp, text ) + text + + + to_char ( timestamp with time zone, text ) + text + + + Converts time stamp to string according to the given format. + + + to_char(timestamp '2002-04-20 17:31:12.66', 'HH12:MI:SS') + 05:31:12 + + + + + + to_char ( interval, text ) + text + + + Converts interval to string according to the given format. + + + to_char(interval '15h 2m 12s', 'HH24:MI:SS') + 15:02:12 + + + + + + to_char ( numeric_type, text ) + text + + + Converts number to string according to the given format; available + for integer, bigint, numeric, + real, double precision. + + + to_char(125, '999') + 125 + + + to_char(125.8::real, '999D9') + 125.8 + + + to_char(-125.8, '999D99S') + 125.80- + + + + + + + to_date + + to_date ( text, text ) + date + + + Converts string to date according to the given format. + + + to_date('05 Dec 2000', 'DD Mon YYYY') + 2000-12-05 + + + + + + + to_number + + to_number ( text, text ) + numeric + + + Converts string to numeric according to the given format. + + + to_number('12,454.8-', '99G999D9S') + -12454.8 + + + + + + + to_timestamp + + to_timestamp ( text, text ) + timestamp with time zone + + + Converts string to time stamp according to the given format. + (See also to_timestamp(double precision) in + .) + + + to_timestamp('05 Dec 2000', 'DD Mon YYYY') + 2000-12-05 00:00:00-05 + + + + +

+ + + + to_timestamp and to_date + exist to handle input formats that cannot be converted by + simple casting. For most standard date/time formats, simply casting the + source string to the required data type works, and is much easier. + Similarly, to_number is unnecessary for standard numeric + representations. + + + + + In a to_char output template string, there are certain + patterns that are recognized and replaced with appropriately-formatted + data based on the given value. Any text that is not a template pattern is + simply copied verbatim. Similarly, in an input template string (for the + other functions), template patterns identify the values to be supplied by + the input data string. If there are characters in the template string + that are not template patterns, the corresponding characters in the input + data string are simply skipped over (whether or not they are equal to the + template string characters). + + + + shows the + template patterns available for formatting date and time values. + + + + Template Patterns for Date/Time Formatting + + + + Pattern + Description + + + + + HH + hour of day (01–12) + + + HH12 + hour of day (01–12) + + + HH24 + hour of day (00–23) + + + MI + minute (00–59) + + + SS + second (00–59) + + + MS + millisecond (000–999) + + + US + microsecond (000000–999999) + + + FF1 + tenth of second (0–9) + + + FF2 + hundredth of second (00–99) + + + FF3 + millisecond (000–999) + + + FF4 + tenth of a millisecond (0000–9999) + + + FF5 + hundredth of a millisecond (00000–99999) + + + FF6 + microsecond (000000–999999) + + + SSSS, SSSSS + seconds past midnight (0–86399) + + + AM, am, + PM or pm + meridiem indicator (without periods) + + + A.M., a.m., + P.M. or p.m. + meridiem indicator (with periods) + + + Y,YYY + year (4 or more digits) with comma + + + YYYY + year (4 or more digits) + + + YYY + last 3 digits of year + + + YY + last 2 digits of year + + + Y + last digit of year + + + IYYY + ISO 8601 week-numbering year (4 or more digits) + + + IYY + last 3 digits of ISO 8601 week-numbering year + + + IY + last 2 digits of ISO 8601 week-numbering year + + + I + last digit of ISO 8601 week-numbering year + + + BC, bc, + AD or ad + era indicator (without periods) + + + B.C., b.c., + A.D. or a.d. + era indicator (with periods) + + + MONTH + full upper case month name (blank-padded to 9 chars) + + + Month + full capitalized month name (blank-padded to 9 chars) + + + month + full lower case month name (blank-padded to 9 chars) + + + MON + abbreviated upper case month name (3 chars in English, localized lengths vary) + + + Mon + abbreviated capitalized month name (3 chars in English, localized lengths vary) + + + mon + abbreviated lower case month name (3 chars in English, localized lengths vary) + + + MM + month number (01–12) + + + DAY + full upper case day name (blank-padded to 9 chars) + + + Day + full capitalized day name (blank-padded to 9 chars) + + + day + full lower case day name (blank-padded to 9 chars) + + + DY + abbreviated upper case day name (3 chars in English, localized lengths vary) + + + Dy + abbreviated capitalized day name (3 chars in English, localized lengths vary) + + + dy + abbreviated lower case day name (3 chars in English, localized lengths vary) + + + DDD + day of year (001–366) + + + IDDD + day of ISO 8601 week-numbering year (001–371; day 1 of the year is Monday of the first ISO week) + + + DD + day of month (01–31) + + + D + day of the week, Sunday (1) to Saturday (7) + + + ID + ISO 8601 day of the week, Monday (1) to Sunday (7) + + + W + week of month (1–5) (the first week starts on the first day of the month) + + + WW + week number of year (1–53) (the first week starts on the first day of the year) + + + IW + week number of ISO 8601 week-numbering year (01–53; the first Thursday of the year is in week 1) + + + CC + century (2 digits) (the twenty-first century starts on 2001-01-01) + + + J + Julian Date (integer days since November 24, 4714 BC at local + midnight; see ) + + + Q + quarter + + + RM + month in upper case Roman numerals (I–XII; I=January) + + + rm + month in lower case Roman numerals (i–xii; i=January) + + + TZ + upper case time-zone abbreviation + + + tz + lower case time-zone abbreviation + + + TZH + time-zone hours + + + TZM + time-zone minutes + + + OF + time-zone offset from UTC (HH + or HH:MM) + + + +

+ + + Modifiers can be applied to any template pattern to alter its + behavior. For example, FMMonth + is the Month pattern with the + FM modifier. + shows the + modifier patterns for date/time formatting. + + + + Template Pattern Modifiers for Date/Time Formatting + + + + Modifier + Description + Example + + + + + FM prefix + fill mode (suppress leading zeroes and padding blanks) + FMMonth + + + TH suffix + upper case ordinal number suffix + DDTH, e.g., 12TH + + + th suffix + lower case ordinal number suffix + DDth, e.g., 12th + + + FX prefix + fixed format global option (see usage notes) + FX Month DD Day + + + TM prefix + translation mode (use localized day and month names based on + ) + TMMonth + + + SP suffix + spell mode (not implemented) + DDSP + + + +

+ + + Usage notes for date/time formatting: + + + + + FM suppresses leading zeroes and trailing blanks + that would otherwise be added to make the output of a pattern be + fixed-width. In PostgreSQL, + FM modifies only the next specification, while in + Oracle FM affects all subsequent + specifications, and repeated FM modifiers + toggle fill mode on and off. + + + + + + TM suppresses trailing blanks whether or + not FM is specified. + + + + + + to_timestamp and to_date + ignore letter case in the input; so for + example MON, Mon, + and mon all accept the same strings. When using + the TM modifier, case-folding is done according to + the rules of the function's input collation (see + ). + + + + + + to_timestamp and to_date + skip multiple blank spaces at the beginning of the input string and + around date and time values unless the FX option is used. For example, + to_timestamp(' 2000 JUN', 'YYYY MON') and + to_timestamp('2000 - JUN', 'YYYY-MON') work, but + to_timestamp('2000 JUN', 'FXYYYY MON') returns an error + because to_timestamp expects only a single space. + FX must be specified as the first item in + the template. + + + + + + A separator (a space or non-letter/non-digit character) in the template string of + to_timestamp and to_date + matches any single separator in the input string or is skipped, + unless the FX option is used. + For example, to_timestamp('2000JUN', 'YYYY///MON') and + to_timestamp('2000/JUN', 'YYYY MON') work, but + to_timestamp('2000//JUN', 'YYYY/MON') + returns an error because the number of separators in the input string + exceeds the number of separators in the template. + + + If FX is specified, a separator in the template string + matches exactly one character in the input string. But note that the + input string character is not required to be the same as the separator from the template string. + For example, to_timestamp('2000/JUN', 'FXYYYY MON') + works, but to_timestamp('2000/JUN', 'FXYYYY MON') + returns an error because the second space in the template string consumes + the letter J from the input string. + + + + + + A TZH template pattern can match a signed number. + Without the FX option, minus signs may be ambiguous, + and could be interpreted as a separator. + This ambiguity is resolved as follows: If the number of separators before + TZH in the template string is less than the number of + separators before the minus sign in the input string, the minus sign + is interpreted as part of TZH. + Otherwise, the minus sign is considered to be a separator between values. + For example, to_timestamp('2000 -10', 'YYYY TZH') matches + -10 to TZH, but + to_timestamp('2000 -10', 'YYYY TZH') + matches 10 to TZH. + + + + + + Ordinary text is allowed in to_char + templates and will be output literally. You can put a substring + in double quotes to force it to be interpreted as literal text + even if it contains template patterns. For example, in + '"Hello Year "YYYY', the YYYY + will be replaced by the year data, but the single Y in Year + will not be. + In to_date, to_number, + and to_timestamp, literal text and double-quoted + strings result in skipping the number of characters contained in the + string; for example "XX" skips two input characters + (whether or not they are XX). + + + + Prior to PostgreSQL 12, it was possible to + skip arbitrary text in the input string using non-letter or non-digit + characters. For example, + to_timestamp('2000y6m1d', 'yyyy-MM-DD') used to + work. Now you can only use letter characters for this purpose. For example, + to_timestamp('2000y6m1d', 'yyyytMMtDDt') and + to_timestamp('2000y6m1d', 'yyyy"y"MM"m"DD"d"') + skip y, m, and + d. + + + + + + + If you want to have a double quote in the output you must + precede it with a backslash, for example '\"YYYY + Month\"'. + Backslashes are not otherwise special outside of double-quoted + strings. Within a double-quoted string, a backslash causes the + next character to be taken literally, whatever it is (but this + has no special effect unless the next character is a double quote + or another backslash). + + + + + + In to_timestamp and to_date, + if the year format specification is less than four digits, e.g., + YYY, and the supplied year is less than four digits, + the year will be adjusted to be nearest to the year 2020, e.g., + 95 becomes 1995. + + + + + + In to_timestamp and to_date, + negative years are treated as signifying BC. If you write both a + negative year and an explicit BC field, you get AD + again. An input of year zero is treated as 1 BC. + + + + + + In to_timestamp and to_date, + the YYYY conversion has a restriction when + processing years with more than 4 digits. You must + use some non-digit character or template after YYYY, + otherwise the year is always interpreted as 4 digits. For example + (with the year 20000): + to_date('200001130', 'YYYYMMDD') will be + interpreted as a 4-digit year; instead use a non-digit + separator after the year, like + to_date('20000-1130', 'YYYY-MMDD') or + to_date('20000Nov30', 'YYYYMonDD'). + + + + + + In to_timestamp and to_date, + the CC (century) field is accepted but ignored + if there is a YYY, YYYY or + Y,YYY field. If CC is used with + YY or Y then the result is + computed as that year in the specified century. If the century is + specified but the year is not, the first year of the century + is assumed. + + + + + + In to_timestamp and to_date, + weekday names or numbers (DAY, D, + and related field types) are accepted but are ignored for purposes of + computing the result. The same is true for quarter + (Q) fields. + + + + + + In to_timestamp and to_date, + an ISO 8601 week-numbering date (as distinct from a Gregorian date) + can be specified in one of two ways: + + + + Year, week number, and weekday: for + example to_date('2006-42-4', 'IYYY-IW-ID') + returns the date 2006-10-19. + If you omit the weekday it is assumed to be 1 (Monday). + + + + + Year and day of year: for example to_date('2006-291', + 'IYYY-IDDD') also returns 2006-10-19. + + + + + + Attempting to enter a date using a mixture of ISO 8601 week-numbering + fields and Gregorian date fields is nonsensical, and will cause an + error. In the context of an ISO 8601 week-numbering year, the + concept of a month or day of month has no + meaning. In the context of a Gregorian year, the ISO week has no + meaning. + + + + While to_date will reject a mixture of + Gregorian and ISO week-numbering date + fields, to_char will not, since output format + specifications like YYYY-MM-DD (IYYY-IDDD) can be + useful. But avoid writing something like IYYY-MM-DD; + that would yield surprising results near the start of the year. + (See for more + information.) + + + + + + + In to_timestamp, millisecond + (MS) or microsecond (US) + fields are used as the + seconds digits after the decimal point. For example + to_timestamp('12.3', 'SS.MS') is not 3 milliseconds, + but 300, because the conversion treats it as 12 + 0.3 seconds. + So, for the format SS.MS, the input values + 12.3, 12.30, + and 12.300 specify the + same number of milliseconds. To get three milliseconds, one must write + 12.003, which the conversion treats as + 12 + 0.003 = 12.003 seconds. + + + + Here is a more + complex example: + to_timestamp('15:12:02.020.001230', 'HH24:MI:SS.MS.US') + is 15 hours, 12 minutes, and 2 seconds + 20 milliseconds + + 1230 microseconds = 2.021230 seconds. + + + + + + to_char(..., 'ID')'s day of the week numbering + matches the extract(isodow from ...) function, but + to_char(..., 'D')'s does not match + extract(dow from ...)'s day numbering. + + + + + + to_char(interval) formats HH and + HH12 as shown on a 12-hour clock, for example zero hours + and 36 hours both output as 12, while HH24 + outputs the full hour value, which can exceed 23 in + an interval value. + + + + + + + + shows the + template patterns available for formatting numeric values. + + + + Template Patterns for Numeric Formatting + + + + Pattern + Description + + + + + 9 + digit position (can be dropped if insignificant) + + + 0 + digit position (will not be dropped, even if insignificant) + + + . (period) + decimal point + + + , (comma) + group (thousands) separator + + + PR + negative value in angle brackets + + + S + sign anchored to number (uses locale) + + + L + currency symbol (uses locale) + + + D + decimal point (uses locale) + + + G + group separator (uses locale) + + + MI + minus sign in specified position (if number < 0) + + + PL + plus sign in specified position (if number > 0) + + + SG + plus/minus sign in specified position + + + RN or rn + Roman numeral (values between 1 and 3999) + + + TH or th + ordinal number suffix + + + V + shift specified number of digits (see notes) + + + EEEE + exponent for scientific notation + + + +

+ + + Usage notes for numeric formatting: + + + + + 0 specifies a digit position that will always be printed, + even if it contains a leading/trailing zero. 9 also + specifies a digit position, but if it is a leading zero then it will + be replaced by a space, while if it is a trailing zero and fill mode + is specified then it will be deleted. (For to_number(), + these two pattern characters are equivalent.) + + + + + + If the format provides fewer fractional digits than the number being + formatted, to_char() will round the number to + the specified number of fractional digits. + + + + + + The pattern characters S, L, D, + and G represent the sign, currency symbol, decimal point, + and thousands separator characters defined by the current locale + (see + and ). The pattern characters period + and comma represent those exact characters, with the meanings of + decimal point and thousands separator, regardless of locale. + + + + + + If no explicit provision is made for a sign + in to_char()'s pattern, one column will be reserved for + the sign, and it will be anchored to (appear just left of) the + number. If S appears just left of some 9's, + it will likewise be anchored to the number. + + + + + + A sign formatted using SG, PL, or + MI is not anchored to + the number; for example, + to_char(-12, 'MI9999') produces '- 12' + but to_char(-12, 'S9999') produces ' -12'. + (The Oracle implementation does not allow the use of + MI before 9, but rather + requires that 9 precede + MI.) + + + + + + TH does not convert values less than zero + and does not convert fractional numbers. + + + + + + PL, SG, and + TH are PostgreSQL + extensions. + + + + + + In to_number, if non-data template patterns such + as L or TH are used, the + corresponding number of input characters are skipped, whether or not + they match the template pattern, unless they are data characters + (that is, digits, sign, decimal point, or comma). For + example, TH would skip two non-data characters. + + + + + + V with to_char + multiplies the input values by + 10^n, where + n is the number of digits following + V. V with + to_number divides in a similar manner. + The V can be thought of as marking the position + of an implicit decimal point in the input or output string. + to_char and to_number + do not support the use of + V combined with a decimal point + (e.g., 99.9V99 is not allowed). + + + + + + EEEE (scientific notation) cannot be used in + combination with any of the other formatting patterns or + modifiers other than digit and decimal point patterns, and must be at the end of the format string + (e.g., 9.99EEEE is a valid pattern). + + + + + + In to_number(), the RN + pattern converts Roman numerals (in standard form) to numbers. + Input is case-insensitive, so RN + and rn are equivalent. RN + cannot be used in combination with any other formatting patterns or + modifiers except FM, which is applicable only + in to_char() and is ignored + in to_number(). + + + + + + + Certain modifiers can be applied to any template pattern to alter its + behavior. For example, FM99.99 + is the 99.99 pattern with the + FM modifier. + shows the + modifier patterns for numeric formatting. + + + + Template Pattern Modifiers for Numeric Formatting + + + + Modifier + Description + Example + + + + + FM prefix + fill mode (suppress trailing zeroes and padding blanks) + FM99.99 + + + TH suffix + upper case ordinal number suffix + 999TH + + + th suffix + lower case ordinal number suffix + 999th + + + +

+ + + shows some + examples of the use of the to_char function. + + + + <function>to_char</function> Examples + + + + Expression + Result + + + + + to_char(current_timestamp, 'Day, DD HH12:MI:SS') + 'Tuesday , 06 05:39:18' + + + to_char(current_timestamp, 'FMDay, FMDD HH12:MI:SS') + 'Tuesday, 6 05:39:18' + + + to_char(current_timestamp AT TIME ZONE + 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"') + '2022-12-06T05:39:18Z', + ISO 8601 extended format + + + to_char(-0.1, '99.99') + ' -.10' + + + to_char(-0.1, 'FM9.99') + '-.1' + + + to_char(-0.1, 'FM90.99') + '-0.1' + + + to_char(0.1, '0.9') + ' 0.1' + + + to_char(12, '9990999.9') + ' 0012.0' + + + to_char(12, 'FM9990999.9') + '0012.' + + + to_char(485, '999') + ' 485' + + + to_char(-485, '999') + '-485' + + + to_char(485, '9 9 9') + ' 4 8 5' + + + to_char(1485, '9,999') + ' 1,485' + + + to_char(1485, '9G999') + ' 1 485' + + + to_char(148.5, '999.999') + ' 148.500' + + + to_char(148.5, 'FM999.999') + '148.5' + + + to_char(148.5, 'FM999.990') + '148.500' + + + to_char(148.5, '999D999') + ' 148,500' + + + to_char(3148.5, '9G999D999') + ' 3 148,500' + + + to_char(-485, '999S') + '485-' + + + to_char(-485, '999MI') + '485-' + + + to_char(485, '999MI') + '485 ' + + + to_char(485, 'FM999MI') + '485' + + + to_char(485, 'PL999') + '+485' + + + to_char(485, 'SG999') + '+485' + + + to_char(-485, 'SG999') + '-485' + + + to_char(-485, '9SG99') + '4-85' + + + to_char(-485, '999PR') + '<485>' + + + to_char(485, 'L999') + 'DM 485' + + + to_char(485, 'RN') + ' CDLXXXV' + + + to_char(485, 'FMRN') + 'CDLXXXV' + + + to_char(5.2, 'FMRN') + 'V' + + + to_char(482, '999th') + ' 482nd' + + + to_char(485, '"Good number:"999') + 'Good number: 485' + + + to_char(485.8, '"Pre:"999" Post:" .999') + 'Pre: 485 Post: .800' + + + to_char(12, '99V999') + ' 12000' + + + to_char(12.4, '99V999') + ' 12400' + + + to_char(12.45, '99V9') + ' 125' + + + to_char(0.0004859, '9.99EEEE') + ' 4.86e-04' + + + +

+ + diff --git a/doc/src/sgml/func/func-geometry.sgml b/doc/src/sgml/func/func-geometry.sgml new file mode 100644 index 00000000000..ba203af3bd2 --- /dev/null +++ b/doc/src/sgml/func/func-geometry.sgml @@ -0,0 +1,1261 @@ + + Geometric Functions and Operators + + + The geometric types point, box, + lseg, line, path, + polygon, and circle have a large set of + native support functions and operators, shown in , , and . + + + + Geometric Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + geometric_type + point + geometric_type + + + Adds the coordinates of the second point to those of each + point of the first argument, thus performing translation. + Available for point, box, path, + circle. + + + box '(1,1),(0,0)' + point '(2,0)' + (3,1),(2,0) + + + + + + path + path + path + + + Concatenates two open paths (returns NULL if either path is closed). + + + path '[(0,0),(1,1)]' + path '[(2,2),(3,3),(4,4)]' + [(0,0),(1,1),(2,2),(3,3),(4,4)] + + + + + + geometric_type - point + geometric_type + + + Subtracts the coordinates of the second point from those + of each point of the first argument, thus performing translation. + Available for point, box, path, + circle. + + + box '(1,1),(0,0)' - point '(2,0)' + (-1,1),(-2,0) + + + + + + geometric_type * point + geometric_type + + + Multiplies each point of the first argument by the second + point (treating a point as being a complex number + represented by real and imaginary parts, and performing standard + complex multiplication). If one interprets + the second point as a vector, this is equivalent to + scaling the object's size and distance from the origin by the length + of the vector, and rotating it counterclockwise around the origin by + the vector's angle from the x axis. + Available for point, box,Rotating a + box with these operators only moves its corner points: the box is + still considered to have sides parallel to the axes. Hence the box's + size is not preserved, as a true rotation would do. + path, circle. + + + path '((0,0),(1,0),(1,1))' * point '(3.0,0)' + ((0,0),(3,0),(3,3)) + + + path '((0,0),(1,0),(1,1))' * point(cosd(45), sind(45)) + ((0,0),&zwsp;(0.7071067811865475,0.7071067811865475),&zwsp;(0,1.414213562373095)) + + + + + + geometric_type / point + geometric_type + + + Divides each point of the first argument by the second + point (treating a point as being a complex number + represented by real and imaginary parts, and performing standard + complex division). If one interprets + the second point as a vector, this is equivalent to + scaling the object's size and distance from the origin down by the + length of the vector, and rotating it clockwise around the origin by + the vector's angle from the x axis. + Available for point, box, path, + circle. + + + path '((0,0),(1,0),(1,1))' / point '(2.0,0)' + ((0,0),(0.5,0),(0.5,0.5)) + + + path '((0,0),(1,0),(1,1))' / point(cosd(45), sind(45)) + ((0,0),&zwsp;(0.7071067811865476,-0.7071067811865476),&zwsp;(1.4142135623730951,0)) + + + + + + @-@ geometric_type + double precision + + + Computes the total length. + Available for lseg, path. + + + @-@ path '[(0,0),(1,0),(1,1)]' + 2 + + + + + + @@ geometric_type + point + + + Computes the center point. + Available for box, lseg, + polygon, circle. + + + @@ box '(2,2),(0,0)' + (1,1) + + + + + + # geometric_type + integer + + + Returns the number of points. + Available for path, polygon. + + + # path '((1,0),(0,1),(-1,0))' + 3 + + + + + + geometric_type # geometric_type + point + + + Computes the point of intersection, or NULL if there is none. + Available for lseg, line. + + + lseg '[(0,0),(1,1)]' # lseg '[(1,0),(0,1)]' + (0.5,0.5) + + + + + + box # box + box + + + Computes the intersection of two boxes, or NULL if there is none. + + + box '(2,2),(-1,-1)' # box '(1,1),(-2,-2)' + (1,1),(-1,-1) + + + + + + geometric_type ## geometric_type + point + + + Computes the closest point to the first object on the second object. + Available for these pairs of types: + (point, box), + (point, lseg), + (point, line), + (lseg, box), + (lseg, lseg), + (line, lseg). + + + point '(0,0)' ## lseg '[(2,0),(0,2)]' + (1,1) + + + + + + geometric_type <-> geometric_type + double precision + + + Computes the distance between the objects. + Available for all seven geometric types, for all combinations + of point with another geometric type, and for + these additional pairs of types: + (box, lseg), + (lseg, line), + (polygon, circle) + (and the commutator cases). + + + circle '<(0,0),1>' <-> circle '<(5,0),1>' + 3 + + + + + + geometric_type @> geometric_type + boolean + + + Does first object contain second? + Available for these pairs of types: + (box, point), + (box, box), + (path, point), + (polygon, point), + (polygon, polygon), + (circle, point), + (circle, circle). + + + circle '<(0,0),2>' @> point '(1,1)' + t + + + + + + geometric_type <@ geometric_type + boolean + + + Is first object contained in or on second? + Available for these pairs of types: + (point, box), + (point, lseg), + (point, line), + (point, path), + (point, polygon), + (point, circle), + (box, box), + (lseg, box), + (lseg, line), + (polygon, polygon), + (circle, circle). + + + point '(1,1)' <@ circle '<(0,0),2>' + t + + + + + + geometric_type && geometric_type + boolean + + + Do these objects overlap? (One point in common makes this true.) + Available for box, polygon, + circle. + + + box '(1,1),(0,0)' && box '(2,2),(0,0)' + t + + + + + + geometric_type << geometric_type + boolean + + + Is first object strictly left of second? + Available for point, box, + polygon, circle. + + + circle '<(0,0),1>' << circle '<(5,0),1>' + t + + + + + + geometric_type >> geometric_type + boolean + + + Is first object strictly right of second? + Available for point, box, + polygon, circle. + + + circle '<(5,0),1>' >> circle '<(0,0),1>' + t + + + + + + geometric_type &< geometric_type + boolean + + + Does first object not extend to the right of second? + Available for box, polygon, + circle. + + + box '(1,1),(0,0)' &< box '(2,2),(0,0)' + t + + + + + + geometric_type &> geometric_type + boolean + + + Does first object not extend to the left of second? + Available for box, polygon, + circle. + + + box '(3,3),(0,0)' &> box '(2,2),(0,0)' + t + + + + + + geometric_type <<| geometric_type + boolean + + + Is first object strictly below second? + Available for point, box, polygon, + circle. + + + box '(3,3),(0,0)' <<| box '(5,5),(3,4)' + t + + + + + + geometric_type |>> geometric_type + boolean + + + Is first object strictly above second? + Available for point, box, polygon, + circle. + + + box '(5,5),(3,4)' |>> box '(3,3),(0,0)' + t + + + + + + geometric_type &<| geometric_type + boolean + + + Does first object not extend above second? + Available for box, polygon, + circle. + + + box '(1,1),(0,0)' &<| box '(2,2),(0,0)' + t + + + + + + geometric_type |&> geometric_type + boolean + + + Does first object not extend below second? + Available for box, polygon, + circle. + + + box '(3,3),(0,0)' |&> box '(2,2),(0,0)' + t + + + + + + box <^ box + boolean + + + Is first object below second (allows edges to touch)? + + + box '((1,1),(0,0))' <^ box '((2,2),(1,1))' + t + + + + + + box >^ box + boolean + + + Is first object above second (allows edges to touch)? + + + box '((2,2),(1,1))' >^ box '((1,1),(0,0))' + t + + + + + + geometric_type ?# geometric_type + boolean + + + Do these objects intersect? + Available for these pairs of types: + (box, box), + (lseg, box), + (lseg, lseg), + (lseg, line), + (line, box), + (line, line), + (path, path). + + + lseg '[(-1,0),(1,0)]' ?# box '(2,2),(-2,-2)' + t + + + + + + ?- line + boolean + + + ?- lseg + boolean + + + Is line horizontal? + + + ?- lseg '[(-1,0),(1,0)]' + t + + + + + + point ?- point + boolean + + + Are points horizontally aligned (that is, have same y coordinate)? + + + point '(1,0)' ?- point '(0,0)' + t + + + + + + ?| line + boolean + + + ?| lseg + boolean + + + Is line vertical? + + + ?| lseg '[(-1,0),(1,0)]' + f + + + + + + point ?| point + boolean + + + Are points vertically aligned (that is, have same x coordinate)? + + + point '(0,1)' ?| point '(0,0)' + t + + + + + + line ?-| line + boolean + + + lseg ?-| lseg + boolean + + + Are lines perpendicular? + + + lseg '[(0,0),(0,1)]' ?-| lseg '[(0,0),(1,0)]' + t + + + + + + line ?|| line + boolean + + + lseg ?|| lseg + boolean + + + Are lines parallel? + + + lseg '[(-1,0),(1,0)]' ?|| lseg '[(-1,2),(1,2)]' + t + + + + + + geometric_type ~= geometric_type + boolean + + + Are these objects the same? + Available for point, box, + polygon, circle. + + + polygon '((0,0),(1,1))' ~= polygon '((1,1),(0,0))' + t + + + + +

+ + + + Note that the same as operator, ~=, + represents the usual notion of equality for the point, + box, polygon, and circle types. + Some of the geometric types also have an = operator, but + = compares for equal areas only. + The other scalar comparison operators (<= and so + on), where available for these types, likewise compare areas. + + + + + + Before PostgreSQL 14, the point + is strictly below/above comparison operators point + <<| point and point + |>> point were respectively + called <^ and >^. These + names are still available, but are deprecated and will eventually be + removed. + + + + + Geometric Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + area + + area ( geometric_type ) + double precision + + + Computes area. + Available for box, path, circle. + A path input must be closed, else NULL is returned. + Also, if the path is self-intersecting, the result may be + meaningless. + + + area(box '(2,2),(0,0)') + 4 + + + + + + + center + + center ( geometric_type ) + point + + + Computes center point. + Available for box, circle. + + + center(box '(1,2),(0,0)') + (0.5,1) + + + + + + + diagonal + + diagonal ( box ) + lseg + + + Extracts box's diagonal as a line segment + (same as lseg(box)). + + + diagonal(box '(1,2),(0,0)') + [(1,2),(0,0)] + + + + + + + diameter + + diameter ( circle ) + double precision + + + Computes diameter of circle. + + + diameter(circle '<(0,0),2>') + 4 + + + + + + + height + + height ( box ) + double precision + + + Computes vertical size of box. + + + height(box '(1,2),(0,0)') + 2 + + + + + + + isclosed + + isclosed ( path ) + boolean + + + Is path closed? + + + isclosed(path '((0,0),(1,1),(2,0))') + t + + + + + + + isopen + + isopen ( path ) + boolean + + + Is path open? + + + isopen(path '[(0,0),(1,1),(2,0)]') + t + + + + + + + length + + length ( geometric_type ) + double precision + + + Computes the total length. + Available for lseg, path. + + + length(path '((-1,0),(1,0))') + 4 + + + + + + + npoints + + npoints ( geometric_type ) + integer + + + Returns the number of points. + Available for path, polygon. + + + npoints(path '[(0,0),(1,1),(2,0)]') + 3 + + + + + + + pclose + + pclose ( path ) + path + + + Converts path to closed form. + + + pclose(path '[(0,0),(1,1),(2,0)]') + ((0,0),(1,1),(2,0)) + + + + + + + popen + + popen ( path ) + path + + + Converts path to open form. + + + popen(path '((0,0),(1,1),(2,0))') + [(0,0),(1,1),(2,0)] + + + + + + + radius + + radius ( circle ) + double precision + + + Computes radius of circle. + + + radius(circle '<(0,0),2>') + 2 + + + + + + + slope + + slope ( point, point ) + double precision + + + Computes slope of a line drawn through the two points. + + + slope(point '(0,0)', point '(2,1)') + 0.5 + + + + + + + width + + width ( box ) + double precision + + + Computes horizontal size of box. + + + width(box '(1,2),(0,0)') + 1 + + + + +

+ + + Geometric Type Conversion Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + box + + box ( circle ) + box + + + Computes box inscribed within the circle. + + + box(circle '<(0,0),2>') + (1.414213562373095,1.414213562373095),&zwsp;(-1.414213562373095,-1.414213562373095) + + + + + + box ( point ) + box + + + Converts point to empty box. + + + box(point '(1,0)') + (1,0),(1,0) + + + + + + box ( point, point ) + box + + + Converts any two corner points to box. + + + box(point '(0,1)', point '(1,0)') + (1,1),(0,0) + + + + + + box ( polygon ) + box + + + Computes bounding box of polygon. + + + box(polygon '((0,0),(1,1),(2,0))') + (2,1),(0,0) + + + + + + + bound_box + + bound_box ( box, box ) + box + + + Computes bounding box of two boxes. + + + bound_box(box '(1,1),(0,0)', box '(4,4),(3,3)') + (4,4),(0,0) + + + + + + + circle + + circle ( box ) + circle + + + Computes smallest circle enclosing box. + + + circle(box '(1,1),(0,0)') + <(0.5,0.5),0.7071067811865476> + + + + + + circle ( point, double precision ) + circle + + + Constructs circle from center and radius. + + + circle(point '(0,0)', 2.0) + <(0,0),2> + + + + + + circle ( polygon ) + circle + + + Converts polygon to circle. The circle's center is the mean of the + positions of the polygon's points, and the radius is the average + distance of the polygon's points from that center. + + + circle(polygon '((0,0),(1,3),(2,0))') + <(1,1),1.6094757082487299> + + + + + + + line + + line ( point, point ) + line + + + Converts two points to the line through them. + + + line(point '(-1,0)', point '(1,0)') + {0,-1,0} + + + + + + + lseg + + lseg ( box ) + lseg + + + Extracts box's diagonal as a line segment. + + + lseg(box '(1,0),(-1,0)') + [(1,0),(-1,0)] + + + + + + lseg ( point, point ) + lseg + + + Constructs line segment from two endpoints. + + + lseg(point '(-1,0)', point '(1,0)') + [(-1,0),(1,0)] + + + + + + + path + + path ( polygon ) + path + + + Converts polygon to a closed path with the same list of points. + + + path(polygon '((0,0),(1,1),(2,0))') + ((0,0),(1,1),(2,0)) + + + + + + + point + + point ( double precision, double precision ) + point + + + Constructs point from its coordinates. + + + point(23.4, -44.5) + (23.4,-44.5) + + + + + + point ( box ) + point + + + Computes center of box. + + + point(box '(1,0),(-1,0)') + (0,0) + + + + + + point ( circle ) + point + + + Computes center of circle. + + + point(circle '<(0,0),2>') + (0,0) + + + + + + point ( lseg ) + point + + + Computes center of line segment. + + + point(lseg '[(-1,0),(1,0)]') + (0,0) + + + + + + point ( polygon ) + point + + + Computes center of polygon (the mean of the + positions of the polygon's points). + + + point(polygon '((0,0),(1,1),(2,0))') + (1,0.3333333333333333) + + + + + + + polygon + + polygon ( box ) + polygon + + + Converts box to a 4-point polygon. + + + polygon(box '(1,1),(0,0)') + ((0,0),(0,1),(1,1),(1,0)) + + + + + + polygon ( circle ) + polygon + + + Converts circle to a 12-point polygon. + + + polygon(circle '<(0,0),2>') + ((-2,0),&zwsp;(-1.7320508075688774,0.9999999999999999),&zwsp;(-1.0000000000000002,1.7320508075688772),&zwsp;(-1.2246063538223773e-16,2),&zwsp;(0.9999999999999996,1.7320508075688774),&zwsp;(1.732050807568877,1.0000000000000007),&zwsp;(2,2.4492127076447545e-16),&zwsp;(1.7320508075688776,-0.9999999999999994),&zwsp;(1.0000000000000009,-1.7320508075688767),&zwsp;(3.673819061467132e-16,-2),&zwsp;(-0.9999999999999987,-1.732050807568878),&zwsp;(-1.7320508075688767,-1.0000000000000009)) + + + + + + polygon ( integer, circle ) + polygon + + + Converts circle to an n-point polygon. + + + polygon(4, circle '<(3,0),1>') + ((2,0),&zwsp;(3,1),&zwsp;(4,1.2246063538223773e-16),&zwsp;(3,-1)) + + + + + + polygon ( path ) + polygon + + + Converts closed path to a polygon with the same list of points. + + + polygon(path '((0,0),(1,1),(2,0))') + ((0,0),(1,1),(2,0)) + + + + + +

+ + + It is possible to access the two component numbers of a point + as though the point were an array with indexes 0 and 1. For example, if + t.p is a point column then + SELECT p[0] FROM t retrieves the X coordinate and + UPDATE t SET p[1] = ... changes the Y coordinate. + In the same way, a value of type box or lseg can be treated + as an array of two point values. + + + diff --git a/doc/src/sgml/func/func-info.sgml b/doc/src/sgml/func/func-info.sgml new file mode 100644 index 00000000000..b507bfaf64b --- /dev/null +++ b/doc/src/sgml/func/func-info.sgml @@ -0,0 +1,3790 @@ + + System Information Functions and Operators + + + The functions described in this section are used to obtain various + information about a PostgreSQL installation. + + + + Session Information Functions + + + shows several + functions that extract session and system information. + + + + In addition to the functions listed in this section, there are a number of + functions related to the statistics system that also provide system + information. See for more + information. + + + + Session Information Functions + + + + + Function + + + Description + + + + + + + + + current_catalog + + current_catalog + name + + + + current_database + + current_database () + name + + + Returns the name of the current database. (Databases are + called catalogs in the SQL standard, + so current_catalog is the standard's + spelling.) + + + + + + + current_query + + current_query () + text + + + Returns the text of the currently executing query, as submitted + by the client (which might contain more than one statement). + + + + + + + current_role + + current_role + name + + + This is equivalent to current_user. + + + + + + + current_schema + + + schema + current + + current_schema + name + + + current_schema () + name + + + Returns the name of the schema that is first in the search path (or a + null value if the search path is empty). This is the schema that will + be used for any tables or other named objects that are created without + specifying a target schema. + + + + + + + current_schemas + + + search path + current + + current_schemas ( include_implicit boolean ) + name[] + + + Returns an array of the names of all schemas presently in the + effective search path, in their priority order. (Items in the current + setting that do not correspond to + existing, searchable schemas are omitted.) If the Boolean argument + is true, then implicitly-searched system schemas + such as pg_catalog are included in the result. + + + + + + + current_user + + + user + current + + current_user + name + + + Returns the user name of the current execution context. + + + + + + + inet_client_addr + + inet_client_addr () + inet + + + Returns the IP address of the current client, + or NULL if the current connection is via a + Unix-domain socket. + + + + + + + inet_client_port + + inet_client_port () + integer + + + Returns the IP port number of the current client, + or NULL if the current connection is via a + Unix-domain socket. + + + + + + + inet_server_addr + + inet_server_addr () + inet + + + Returns the IP address on which the server accepted the current + connection, + or NULL if the current connection is via a + Unix-domain socket. + + + + + + + inet_server_port + + inet_server_port () + integer + + + Returns the IP port number on which the server accepted the current + connection, + or NULL if the current connection is via a + Unix-domain socket. + + + + + + + pg_backend_pid + + pg_backend_pid () + integer + + + Returns the process ID of the server process attached to the current + session. + + + + + + + pg_blocking_pids + + pg_blocking_pids ( integer ) + integer[] + + + Returns an array of the process ID(s) of the sessions that are + blocking the server process with the specified process ID from + acquiring a lock, or an empty array if there is no such server process + or it is not blocked. + + + One server process blocks another if it either holds a lock that + conflicts with the blocked process's lock request (hard block), or is + waiting for a lock that would conflict with the blocked process's lock + request and is ahead of it in the wait queue (soft block). When using + parallel queries the result always lists client-visible process IDs + (that is, pg_backend_pid results) even if the + actual lock is held or awaited by a child worker process. As a result + of that, there may be duplicated PIDs in the result. Also note that + when a prepared transaction holds a conflicting lock, it will be + represented by a zero process ID. + + + Frequent calls to this function could have some impact on database + performance, because it needs exclusive access to the lock manager's + shared state for a short time. + + + + + + + pg_conf_load_time + + pg_conf_load_time () + timestamp with time zone + + + Returns the time when the server configuration files were last loaded. + If the current session was alive at the time, this will be the time + when the session itself re-read the configuration files (so the + reading will vary a little in different sessions). Otherwise it is + the time when the postmaster process re-read the configuration files. + + + + + + + pg_current_logfile + + + Logging + pg_current_logfile function + + + current_logfiles + and the pg_current_logfile function + + + Logging + current_logfiles file and the pg_current_logfile + function + + pg_current_logfile ( text ) + text + + + Returns the path name of the log file currently in use by the logging + collector. The path includes the + directory and the individual log file name. The result + is NULL if the logging collector is disabled. + When multiple log files exist, each in a different + format, pg_current_logfile without an argument + returns the path of the file having the first format found in the + ordered list: stderr, + csvlog, jsonlog. + NULL is returned if no log file has any of these + formats. + To request information about a specific log file format, supply + either csvlog, jsonlog or + stderr as the + value of the optional parameter. The result is NULL + if the log format requested is not configured in + . + The result reflects the contents of + the current_logfiles file. + + + This function is restricted to superusers and roles with privileges of + the pg_monitor role by default, but other users can + be granted EXECUTE to run the function. + + + + + + + pg_get_loaded_modules + + pg_get_loaded_modules () + setof record + ( module_name text, + version text, + file_name text ) + + + Returns a list of the loadable modules that are loaded into the + current server session. The module_name + and version fields are NULL unless the + module author supplied values for them using + the PG_MODULE_MAGIC_EXT macro. + The file_name field gives the file + name of the module (shared library). + + + + + + + pg_my_temp_schema + + pg_my_temp_schema () + oid + + + Returns the OID of the current session's temporary schema, or zero if + it has none (because it has not created any temporary tables). + + + + + + + pg_is_other_temp_schema + + pg_is_other_temp_schema ( oid ) + boolean + + + Returns true if the given OID is the OID of another session's + temporary schema. (This can be useful, for example, to exclude other + sessions' temporary tables from a catalog display.) + + + + + + + pg_jit_available + + pg_jit_available () + boolean + + + Returns true if a JIT compiler extension is + available (see ) and the + configuration parameter is set to + on. + + + + + + + pg_numa_available + + pg_numa_available () + boolean + + + Returns true if the server has been compiled with NUMA support. + + + + + + + pg_listening_channels + + pg_listening_channels () + setof text + + + Returns the set of names of asynchronous notification channels that + the current session is listening to. + + + + + + + pg_notification_queue_usage + + pg_notification_queue_usage () + double precision + + + Returns the fraction (0–1) of the asynchronous notification + queue's maximum size that is currently occupied by notifications that + are waiting to be processed. + See and + for more information. + + + + + + + pg_postmaster_start_time + + pg_postmaster_start_time () + timestamp with time zone + + + Returns the time when the server started. + + + + + + + pg_safe_snapshot_blocking_pids + + pg_safe_snapshot_blocking_pids ( integer ) + integer[] + + + Returns an array of the process ID(s) of the sessions that are blocking + the server process with the specified process ID from acquiring a safe + snapshot, or an empty array if there is no such server process or it + is not blocked. + + + A session running a SERIALIZABLE transaction blocks + a SERIALIZABLE READ ONLY DEFERRABLE transaction + from acquiring a snapshot until the latter determines that it is safe + to avoid taking any predicate locks. See + for more information about + serializable and deferrable transactions. + + + Frequent calls to this function could have some impact on database + performance, because it needs access to the predicate lock manager's + shared state for a short time. + + + + + + + pg_trigger_depth + + pg_trigger_depth () + integer + + + Returns the current nesting level + of PostgreSQL triggers (0 if not called, + directly or indirectly, from inside a trigger). + + + + + + + session_user + + session_user + name + + + Returns the session user's name. + + + + + + + system_user + + system_user + text + + + Returns the authentication method and the identity (if any) that the + user presented during the authentication cycle before they were + assigned a database role. It is represented as + auth_method:identity or + NULL if the user has not been authenticated (for + example if Trust authentication has + been used). + + + + + + + user + + user + name + + + This is equivalent to current_user. + + + + +

+ + + + current_catalog, + current_role, + current_schema, + current_user, + session_user, + and user have special syntactic status + in SQL: they must be called without trailing + parentheses. In PostgreSQL, parentheses can optionally be used with + current_schema, but not with the others. + + + + + The session_user is normally the user who initiated + the current database connection; but superusers can change this setting + with . + The current_user is the user identifier + that is applicable for permission checking. Normally it is equal + to the session user, but it can be changed with + . + It also changes during the execution of + functions with the attribute SECURITY DEFINER. + In Unix parlance, the session user is the real user and + the current user is the effective user. + current_role and user are + synonyms for current_user. (The SQL standard draws + a distinction between current_role + and current_user, but PostgreSQL + does not, since it unifies users and roles into a single kind of entity.) + + + + + + Access Privilege Inquiry Functions + + + privilege + querying + + + + lists functions that + allow querying object access privileges programmatically. + (See for more information about + privileges.) + In these functions, the user whose privileges are being inquired about + can be specified by name or by OID + (pg_authid.oid), or if + the name is given as public then the privileges of the + PUBLIC pseudo-role are checked. Also, the user + argument can be omitted entirely, in which case + the current_user is assumed. + The object that is being inquired about can be specified either by name or + by OID, too. When specifying by name, a schema name can be included if + relevant. + The access privilege of interest is specified by a text string, which must + evaluate to one of the appropriate privilege keywords for the object's type + (e.g., SELECT). Optionally, WITH GRANT + OPTION can be added to a privilege type to test whether the + privilege is held with grant option. Also, multiple privilege types can be + listed separated by commas, in which case the result will be true if any of + the listed privileges is held. (Case of the privilege string is not + significant, and extra whitespace is allowed between but not within + privilege names.) + Some examples: + +SELECT has_table_privilege('myschema.mytable', 'select'); +SELECT has_table_privilege('joe', 'mytable', 'INSERT, SELECT WITH GRANT OPTION'); + + + + + Access Privilege Inquiry Functions + + + + + Function + + + Description + + + + + + + + + has_any_column_privilege + + has_any_column_privilege ( + user name or oid, + table text or oid, + privilege text ) + boolean + + + Does user have privilege for any column of table? + This succeeds either if the privilege is held for the whole table, or + if there is a column-level grant of the privilege for at least one + column. + Allowable privilege types are + SELECT, INSERT, + UPDATE, and REFERENCES. + + + + + + + has_column_privilege + + has_column_privilege ( + user name or oid, + table text or oid, + column text or smallint, + privilege text ) + boolean + + + Does user have privilege for the specified table column? + This succeeds either if the privilege is held for the whole table, or + if there is a column-level grant of the privilege for the column. + The column can be specified by name or by attribute number + (pg_attribute.attnum). + Allowable privilege types are + SELECT, INSERT, + UPDATE, and REFERENCES. + + + + + + + has_database_privilege + + has_database_privilege ( + user name or oid, + database text or oid, + privilege text ) + boolean + + + Does user have privilege for database? + Allowable privilege types are + CREATE, + CONNECT, + TEMPORARY, and + TEMP (which is equivalent to + TEMPORARY). + + + + + + + has_foreign_data_wrapper_privilege + + has_foreign_data_wrapper_privilege ( + user name or oid, + fdw text or oid, + privilege text ) + boolean + + + Does user have privilege for foreign-data wrapper? + The only allowable privilege type is USAGE. + + + + + + + has_function_privilege + + has_function_privilege ( + user name or oid, + function text or oid, + privilege text ) + boolean + + + Does user have privilege for function? + The only allowable privilege type is EXECUTE. + + + When specifying a function by name rather than by OID, the allowed + input is the same as for the regprocedure data type (see + ). + An example is: + +SELECT has_function_privilege('joeuser', 'myfunc(int, text)', 'execute'); + + + + + + + + has_language_privilege + + has_language_privilege ( + user name or oid, + language text or oid, + privilege text ) + boolean + + + Does user have privilege for language? + The only allowable privilege type is USAGE. + + + + + + + has_largeobject_privilege + + has_largeobject_privilege ( + user name or oid, + largeobject oid, + privilege text ) + boolean + + + Does user have privilege for large object? + Allowable privilege types are + SELECT and UPDATE. + + + + + + + has_parameter_privilege + + has_parameter_privilege ( + user name or oid, + parameter text, + privilege text ) + boolean + + + Does user have privilege for configuration parameter? + The parameter name is case-insensitive. + Allowable privilege types are SET + and ALTER SYSTEM. + + + + + + + has_schema_privilege + + has_schema_privilege ( + user name or oid, + schema text or oid, + privilege text ) + boolean + + + Does user have privilege for schema? + Allowable privilege types are + CREATE and + USAGE. + + + + + + + has_sequence_privilege + + has_sequence_privilege ( + user name or oid, + sequence text or oid, + privilege text ) + boolean + + + Does user have privilege for sequence? + Allowable privilege types are + USAGE, + SELECT, and + UPDATE. + + + + + + + has_server_privilege + + has_server_privilege ( + user name or oid, + server text or oid, + privilege text ) + boolean + + + Does user have privilege for foreign server? + The only allowable privilege type is USAGE. + + + + + + + has_table_privilege + + has_table_privilege ( + user name or oid, + table text or oid, + privilege text ) + boolean + + + Does user have privilege for table? + Allowable privilege types + are SELECT, INSERT, + UPDATE, DELETE, + TRUNCATE, REFERENCES, + TRIGGER, and MAINTAIN. + + + + + + + has_tablespace_privilege + + has_tablespace_privilege ( + user name or oid, + tablespace text or oid, + privilege text ) + boolean + + + Does user have privilege for tablespace? + The only allowable privilege type is CREATE. + + + + + + + has_type_privilege + + has_type_privilege ( + user name or oid, + type text or oid, + privilege text ) + boolean + + + Does user have privilege for data type? + The only allowable privilege type is USAGE. + When specifying a type by name rather than by OID, the allowed input + is the same as for the regtype data type (see + ). + + + + + + + pg_has_role + + pg_has_role ( + user name or oid, + role text or oid, + privilege text ) + boolean + + + Does user have privilege for role? + Allowable privilege types are + MEMBER, USAGE, + and SET. + MEMBER denotes direct or indirect membership in + the role without regard to what specific privileges may be conferred. + USAGE denotes whether the privileges of the role + are immediately available without doing SET ROLE, + while SET denotes whether it is possible to change + to the role using the SET ROLE command. + WITH ADMIN OPTION or WITH GRANT + OPTION can be added to any of these privilege types to + test whether the ADMIN privilege is held (all + six spellings test the same thing). + This function does not allow the special case of + setting user to public, + because the PUBLIC pseudo-role can never be a member of real roles. + + + + + + + row_security_active + + row_security_active ( + table text or oid ) + boolean + + + Is row-level security active for the specified table in the context of + the current user and current environment? + + + + +

+ + + shows the operators + available for the aclitem type, which is the catalog + representation of access privileges. See + for information about how to read access privilege values. + + + + <type>aclitem</type> Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + + aclitemeq + + aclitem = aclitem + boolean + + + Are aclitems equal? (Notice that + type aclitem lacks the usual set of comparison + operators; it has only equality. In turn, aclitem + arrays can only be compared for equality.) + + + 'calvin=r*w/hobbes'::aclitem = 'calvin=r*w*/hobbes'::aclitem + f + + + + + + + aclcontains + + aclitem[] @> aclitem + boolean + + + Does array contain the specified privileges? (This is true if there + is an array entry that matches the aclitem's grantee and + grantor, and has at least the specified set of privileges.) + + + '{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] @> 'calvin=r*/hobbes'::aclitem + t + + + + + + aclitem[] ~ aclitem + boolean + + + This is a deprecated alias for @>. + + + '{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] ~ 'calvin=r*/hobbes'::aclitem + t + + + + +

+ + + shows some additional + functions to manage the aclitem type. + + + + <type>aclitem</type> Functions + + + + + Function + + + Description + + + + + + + + + acldefault + + acldefault ( + type "char", + ownerId oid ) + aclitem[] + + + Constructs an aclitem array holding the default access + privileges for an object of type type belonging + to the role with OID ownerId. This represents + the access privileges that will be assumed when an object's + ACL entry is null. (The default access privileges + are described in .) + The type parameter must be one of + 'c' for COLUMN, + 'r' for TABLE and table-like objects, + 's' for SEQUENCE, + 'd' for DATABASE, + 'f' for FUNCTION or PROCEDURE, + 'l' for LANGUAGE, + 'L' for LARGE OBJECT, + 'n' for SCHEMA, + 'p' for PARAMETER, + 't' for TABLESPACE, + 'F' for FOREIGN DATA WRAPPER, + 'S' for FOREIGN SERVER, + or + 'T' for TYPE or DOMAIN. + + + + + + + aclexplode + + aclexplode ( aclitem[] ) + setof record + ( grantor oid, + grantee oid, + privilege_type text, + is_grantable boolean ) + + + Returns the aclitem array as a set of rows. + If the grantee is the pseudo-role PUBLIC, it is represented by zero in + the grantee column. Each granted privilege is + represented as SELECT, INSERT, + etc (see for a full list). + Note that each privilege is broken out as a separate row, so + only one keyword appears in the privilege_type + column. + + + + + + + makeaclitem + + makeaclitem ( + grantee oid, + grantor oid, + privileges text, + is_grantable boolean ) + aclitem + + + Constructs an aclitem with the given properties. + privileges is a comma-separated list of + privilege names such as SELECT, + INSERT, etc, all of which are set in the + result. (Case of the privilege string is not significant, and + extra whitespace is allowed between but not within privilege + names.) + + + + +

+ + + + + Schema Visibility Inquiry Functions + + + shows functions that + determine whether a certain object is visible in the + current schema search path. + For example, a table is said to be visible if its + containing schema is in the search path and no table of the same + name appears earlier in the search path. This is equivalent to the + statement that the table can be referenced by name without explicit + schema qualification. Thus, to list the names of all visible tables: + +SELECT relname FROM pg_class WHERE pg_table_is_visible(oid); + + For functions and operators, an object in the search path is said to be + visible if there is no object of the same name and argument data + type(s) earlier in the path. For operator classes and families, + both the name and the associated index access method are considered. + + + + search path + object visibility + + + + Schema Visibility Inquiry Functions + + + + + Function + + + Description + + + + + + + + + pg_collation_is_visible + + pg_collation_is_visible ( collation oid ) + boolean + + + Is collation visible in search path? + + + + + + + pg_conversion_is_visible + + pg_conversion_is_visible ( conversion oid ) + boolean + + + Is conversion visible in search path? + + + + + + + pg_function_is_visible + + pg_function_is_visible ( function oid ) + boolean + + + Is function visible in search path? + (This also works for procedures and aggregates.) + + + + + + + pg_opclass_is_visible + + pg_opclass_is_visible ( opclass oid ) + boolean + + + Is operator class visible in search path? + + + + + + + pg_operator_is_visible + + pg_operator_is_visible ( operator oid ) + boolean + + + Is operator visible in search path? + + + + + + + pg_opfamily_is_visible + + pg_opfamily_is_visible ( opclass oid ) + boolean + + + Is operator family visible in search path? + + + + + + + pg_statistics_obj_is_visible + + pg_statistics_obj_is_visible ( stat oid ) + boolean + + + Is statistics object visible in search path? + + + + + + + pg_table_is_visible + + pg_table_is_visible ( table oid ) + boolean + + + Is table visible in search path? + (This works for all types of relations, including views, materialized + views, indexes, sequences and foreign tables.) + + + + + + + pg_ts_config_is_visible + + pg_ts_config_is_visible ( config oid ) + boolean + + + Is text search configuration visible in search path? + + + + + + + pg_ts_dict_is_visible + + pg_ts_dict_is_visible ( dict oid ) + boolean + + + Is text search dictionary visible in search path? + + + + + + + pg_ts_parser_is_visible + + pg_ts_parser_is_visible ( parser oid ) + boolean + + + Is text search parser visible in search path? + + + + + + + pg_ts_template_is_visible + + pg_ts_template_is_visible ( template oid ) + boolean + + + Is text search template visible in search path? + + + + + + + pg_type_is_visible + + pg_type_is_visible ( type oid ) + boolean + + + Is type (or domain) visible in search path? + + + + +

+ + + All these functions require object OIDs to identify the object to be + checked. If you want to test an object by name, it is convenient to use + the OID alias types (regclass, regtype, + regprocedure, regoperator, regconfig, + or regdictionary), + for example: + +SELECT pg_type_is_visible('myschema.widget'::regtype); + + Note that it would not make much sense to test a non-schema-qualified + type name in this way — if the name can be recognized at all, it must be visible. + + + + + + System Catalog Information Functions + + + lists functions that + extract information from the system catalogs. + + + + System Catalog Information Functions + + + + + Function + + + Description + + + + + + + + + format_type + + format_type ( type oid, typemod integer ) + text + + + Returns the SQL name for a data type that is identified by its type + OID and possibly a type modifier. Pass NULL for the type modifier if + no specific modifier is known. + + + + + + + pg_basetype + + pg_basetype ( regtype ) + regtype + + + Returns the OID of the base type of a domain identified by its + type OID. If the argument is the OID of a non-domain type, + returns the argument as-is. Returns NULL if the argument is + not a valid type OID. If there's a chain of domain dependencies, + it will recurse until finding the base type. + + + Assuming CREATE DOMAIN mytext AS text: + + + pg_basetype('mytext'::regtype) + text + + + + + + + pg_char_to_encoding + + pg_char_to_encoding ( encoding name ) + integer + + + Converts the supplied encoding name into an integer representing the + internal identifier used in some system catalog tables. + Returns -1 if an unknown encoding name is provided. + + + + + + + pg_encoding_to_char + + pg_encoding_to_char ( encoding integer ) + name + + + Converts the integer used as the internal identifier of an encoding in some + system catalog tables into a human-readable string. + Returns an empty string if an invalid encoding number is provided. + + + + + + + pg_get_catalog_foreign_keys + + pg_get_catalog_foreign_keys () + setof record + ( fktable regclass, + fkcols text[], + pktable regclass, + pkcols text[], + is_array boolean, + is_opt boolean ) + + + Returns a set of records describing the foreign key relationships + that exist within the PostgreSQL system + catalogs. + The fktable column contains the name of the + referencing catalog, and the fkcols column + contains the name(s) of the referencing column(s). Similarly, + the pktable column contains the name of the + referenced catalog, and the pkcols column + contains the name(s) of the referenced column(s). + If is_array is true, the last referencing + column is an array, each of whose elements should match some entry + in the referenced catalog. + If is_opt is true, the referencing column(s) + are allowed to contain zeroes instead of a valid reference. + + + + + + + pg_get_constraintdef + + pg_get_constraintdef ( constraint oid , pretty boolean ) + text + + + Reconstructs the creating command for a constraint. + (This is a decompiled reconstruction, not the original text + of the command.) + + + + + + + pg_get_expr + + pg_get_expr ( expr pg_node_tree, relation oid , pretty boolean ) + text + + + Decompiles the internal form of an expression stored in the system + catalogs, such as the default value for a column. If the expression + might contain Vars, specify the OID of the relation they refer to as + the second parameter; if no Vars are expected, passing zero is + sufficient. + + + + + + + pg_get_functiondef + + pg_get_functiondef ( func oid ) + text + + + Reconstructs the creating command for a function or procedure. + (This is a decompiled reconstruction, not the original text + of the command.) + The result is a complete CREATE OR REPLACE FUNCTION + or CREATE OR REPLACE PROCEDURE statement. + + + + + + + pg_get_function_arguments + + pg_get_function_arguments ( func oid ) + text + + + Reconstructs the argument list of a function or procedure, in the form + it would need to appear in within CREATE FUNCTION + (including default values). + + + + + + + pg_get_function_identity_arguments + + pg_get_function_identity_arguments ( func oid ) + text + + + Reconstructs the argument list necessary to identify a function or + procedure, in the form it would need to appear in within commands such + as ALTER FUNCTION. This form omits default values. + + + + + + + pg_get_function_result + + pg_get_function_result ( func oid ) + text + + + Reconstructs the RETURNS clause of a function, in + the form it would need to appear in within CREATE + FUNCTION. Returns NULL for a procedure. + + + + + + + pg_get_indexdef + + pg_get_indexdef ( index oid , column integer, pretty boolean ) + text + + + Reconstructs the creating command for an index. + (This is a decompiled reconstruction, not the original text + of the command.) If column is supplied and is + not zero, only the definition of that column is reconstructed. + + + + + + + pg_get_keywords + + pg_get_keywords () + setof record + ( word text, + catcode "char", + barelabel boolean, + catdesc text, + baredesc text ) + + + Returns a set of records describing the SQL keywords recognized by the + server. The word column contains the + keyword. The catcode column contains a + category code: U for an unreserved + keyword, C for a keyword that can be a column + name, T for a keyword that can be a type or + function name, or R for a fully reserved keyword. + The barelabel column + contains true if the keyword can be used as + a bare column label in SELECT lists, + or false if it can only be used + after AS. + The catdesc column contains a + possibly-localized string describing the keyword's category. + The baredesc column contains a + possibly-localized string describing the keyword's column label status. + + + + + + + pg_get_partkeydef + + pg_get_partkeydef ( table oid ) + text + + + Reconstructs the definition of a partitioned table's partition + key, in the form it would have in the PARTITION + BY clause of CREATE TABLE. + (This is a decompiled reconstruction, not the original text + of the command.) + + + + + + + pg_get_ruledef + + pg_get_ruledef ( rule oid , pretty boolean ) + text + + + Reconstructs the creating command for a rule. + (This is a decompiled reconstruction, not the original text + of the command.) + + + + + + + pg_get_serial_sequence + + pg_get_serial_sequence ( table text, column text ) + text + + + Returns the name of the sequence associated with a column, + or NULL if no sequence is associated with the column. + If the column is an identity column, the associated sequence is the + sequence internally created for that column. + For columns created using one of the serial types + (serial, smallserial, bigserial), + it is the sequence created for that serial column definition. + In the latter case, the association can be modified or removed + with ALTER SEQUENCE OWNED BY. + (This function probably should have been + called pg_get_owned_sequence; its current name + reflects the fact that it has historically been used with serial-type + columns.) The first parameter is a table name with optional + schema, and the second parameter is a column name. Because the first + parameter potentially contains both schema and table names, it is + parsed per usual SQL rules, meaning it is lower-cased by default. + The second parameter, being just a column name, is treated literally + and so has its case preserved. The result is suitably formatted + for passing to the sequence functions (see + ). + + + A typical use is in reading the current value of the sequence for an + identity or serial column, for example: + +SELECT currval(pg_get_serial_sequence('sometable', 'id')); + + + + + + + + pg_get_statisticsobjdef + + pg_get_statisticsobjdef ( statobj oid ) + text + + + Reconstructs the creating command for an extended statistics object. + (This is a decompiled reconstruction, not the original text + of the command.) + + + + + + + pg_get_triggerdef + +pg_get_triggerdef ( trigger oid , pretty boolean ) + text + + + Reconstructs the creating command for a trigger. + (This is a decompiled reconstruction, not the original text + of the command.) + + + + + + + pg_get_userbyid + + pg_get_userbyid ( role oid ) + name + + + Returns a role's name given its OID. + + + + + + + pg_get_viewdef + + pg_get_viewdef ( view oid , pretty boolean ) + text + + + Reconstructs the underlying SELECT command for a + view or materialized view. (This is a decompiled reconstruction, not + the original text of the command.) + + + + + + pg_get_viewdef ( view oid, wrap_column integer ) + text + + + Reconstructs the underlying SELECT command for a + view or materialized view. (This is a decompiled reconstruction, not + the original text of the command.) In this form of the function, + pretty-printing is always enabled, and long lines are wrapped to try + to keep them shorter than the specified number of columns. + + + + + + pg_get_viewdef ( view text , pretty boolean ) + text + + + Reconstructs the underlying SELECT command for a + view or materialized view, working from a textual name for the view + rather than its OID. (This is deprecated; use the OID variant + instead.) + + + + + + + pg_index_column_has_property + + pg_index_column_has_property ( index regclass, column integer, property text ) + boolean + + + Tests whether an index column has the named property. + Common index column properties are listed in + . + (Note that extension access methods can define additional property + names for their indexes.) + NULL is returned if the property name is not known + or does not apply to the particular object, or if the OID or column + number does not identify a valid object. + + + + + + + pg_index_has_property + + pg_index_has_property ( index regclass, property text ) + boolean + + + Tests whether an index has the named property. + Common index properties are listed in + . + (Note that extension access methods can define additional property + names for their indexes.) + NULL is returned if the property name is not known + or does not apply to the particular object, or if the OID does not + identify a valid object. + + + + + + + pg_indexam_has_property + + pg_indexam_has_property ( am oid, property text ) + boolean + + + Tests whether an index access method has the named property. + Access method properties are listed in + . + NULL is returned if the property name is not known + or does not apply to the particular object, or if the OID does not + identify a valid object. + + + + + + + pg_options_to_table + + pg_options_to_table ( options_array text[] ) + setof record + ( option_name text, + option_value text ) + + + Returns the set of storage options represented by a value from + pg_class.reloptions or + pg_attribute.attoptions. + + + + + + + pg_settings_get_flags + + pg_settings_get_flags ( guc text ) + text[] + + + Returns an array of the flags associated with the given GUC, or + NULL if it does not exist. The result is + an empty array if the GUC exists but there are no flags to show. + Only the most useful flags listed in + are exposed. + + + + + + + pg_tablespace_databases + + pg_tablespace_databases ( tablespace oid ) + setof oid + + + Returns the set of OIDs of databases that have objects stored in the + specified tablespace. If this function returns any rows, the + tablespace is not empty and cannot be dropped. To identify the specific + objects populating the tablespace, you will need to connect to the + database(s) identified by pg_tablespace_databases + and query their pg_class catalogs. + + + + + + + pg_tablespace_location + + pg_tablespace_location ( tablespace oid ) + text + + + Returns the file system path that this tablespace is located in. + + + + + + + pg_typeof + + pg_typeof ( "any" ) + regtype + + + Returns the OID of the data type of the value that is passed to it. + This can be helpful for troubleshooting or dynamically constructing + SQL queries. The function is declared as + returning regtype, which is an OID alias type (see + ); this means that it is the same as an + OID for comparison purposes but displays as a type name. + + + pg_typeof(33) + integer + + + + + + + COLLATION FOR + + COLLATION FOR ( "any" ) + text + + + Returns the name of the collation of the value that is passed to it. + The value is quoted and schema-qualified if necessary. If no + collation was derived for the argument expression, + then NULL is returned. If the argument is not of a + collatable data type, then an error is raised. + + + collation for ('foo'::text) + "default" + + + collation for ('foo' COLLATE "de_DE") + "de_DE" + + + + + + + to_regclass + + to_regclass ( text ) + regclass + + + Translates a textual relation name to its OID. A similar result is + obtained by casting the string to type regclass (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found. + + + + + + + to_regdatabase + + to_regdatabase ( text ) + regdatabase + + + Translates a textual database name to its OID. A similar result is + obtained by casting the string to type regdatabase (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found. + + + + + + + to_regcollation + + to_regcollation ( text ) + regcollation + + + Translates a textual collation name to its OID. A similar result is + obtained by casting the string to type regcollation (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found. + + + + + + + to_regnamespace + + to_regnamespace ( text ) + regnamespace + + + Translates a textual schema name to its OID. A similar result is + obtained by casting the string to type regnamespace (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found. + + + + + + + to_regoper + + to_regoper ( text ) + regoper + + + Translates a textual operator name to its OID. A similar result is + obtained by casting the string to type regoper (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found or is ambiguous. + + + + + + + to_regoperator + + to_regoperator ( text ) + regoperator + + + Translates a textual operator name (with parameter types) to its OID. A similar result is + obtained by casting the string to type regoperator (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found. + + + + + + + to_regproc + + to_regproc ( text ) + regproc + + + Translates a textual function or procedure name to its OID. A similar result is + obtained by casting the string to type regproc (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found or is ambiguous. + + + + + + + to_regprocedure + + to_regprocedure ( text ) + regprocedure + + + Translates a textual function or procedure name (with argument types) to its OID. A similar result is + obtained by casting the string to type regprocedure (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found. + + + + + + + to_regrole + + to_regrole ( text ) + regrole + + + Translates a textual role name to its OID. A similar result is + obtained by casting the string to type regrole (see + ); however, this function will return + NULL rather than throwing an error if the name is + not found. + + + + + + + to_regtype + + to_regtype ( text ) + regtype + + + Parses a string of text, extracts a potential type name from it, + and translates that name into a type OID. A syntax error in the + string will result in an error; but if the string is a + syntactically valid type name that happens not to be found in the + catalogs, the result is NULL. A similar result + is obtained by casting the string to type regtype + (see ), except that that will throw + error for name not found. + + + + + + + to_regtypemod + + to_regtypemod ( text ) + integer + + + Parses a string of text, extracts a potential type name from it, + and translates its type modifier, if any. A syntax error in the + string will result in an error; but if the string is a + syntactically valid type name that happens not to be found in the + catalogs, the result is NULL. The result is + -1 if no type modifier is present. + + + to_regtypemod can be combined with + to produce appropriate inputs for + , allowing a string representing a + type name to be canonicalized. + + + format_type(to_regtype('varchar(32)'), to_regtypemod('varchar(32)')) + character varying(32) + + + + +

+ + + Most of the functions that reconstruct (decompile) database objects + have an optional pretty flag, which + if true causes the result to + be pretty-printed. Pretty-printing suppresses unnecessary + parentheses and adds whitespace for legibility. + The pretty-printed format is more readable, but the default format + is more likely to be interpreted the same way by future versions of + PostgreSQL; so avoid using pretty-printed output + for dump purposes. Passing false for + the pretty parameter yields the same result as + omitting the parameter. + + + + Index Column Properties + + + NameDescription + + + + asc + Does the column sort in ascending order on a forward scan? + + + + desc + Does the column sort in descending order on a forward scan? + + + + nulls_first + Does the column sort with nulls first on a forward scan? + + + + nulls_last + Does the column sort with nulls last on a forward scan? + + + + orderable + Does the column possess any defined sort ordering? + + + + distance_orderable + Can the column be scanned in order by a distance + operator, for example ORDER BY col <-> constant ? + + + + returnable + Can the column value be returned by an index-only scan? + + + + search_array + Does the column natively support col = ANY(array) + searches? + + + + search_nulls + Does the column support IS NULL and + IS NOT NULL searches? + + + + +

+ + + Index Properties + + + NameDescription + + + + clusterable + Can the index be used in a CLUSTER command? + + + + index_scan + Does the index support plain (non-bitmap) scans? + + + + bitmap_scan + Does the index support bitmap scans? + + + + backward_scan + Can the scan direction be changed in mid-scan (to + support FETCH BACKWARD on a cursor without + needing materialization)? + + + + +

+ + + Index Access Method Properties + + + NameDescription + + + + can_order + Does the access method support ASC, + DESC and related keywords in + CREATE INDEX? + + + + can_unique + Does the access method support unique indexes? + + + + can_multi_col + Does the access method support indexes with multiple columns? + + + + can_exclude + Does the access method support exclusion constraints? + + + + can_include + Does the access method support the INCLUDE + clause of CREATE INDEX? + + + + +

+ + + GUC Flags + + + FlagDescription + + + + EXPLAIN + Parameters with this flag are included in + EXPLAIN (SETTINGS) commands. + + + + NO_SHOW_ALL + Parameters with this flag are excluded from + SHOW ALL commands. + + + + NO_RESET + Parameters with this flag do not support + RESET commands. + + + + NO_RESET_ALL + Parameters with this flag are excluded from + RESET ALL commands. + + + + NOT_IN_SAMPLE + Parameters with this flag are not included in + postgresql.conf by default. + + + + RUNTIME_COMPUTED + Parameters with this flag are runtime-computed ones. + + + + +

+ + + + + Object Information and Addressing Functions + + + lists functions related to + database object identification and addressing. + + + + Object Information and Addressing Functions + + + + + Function + + + Description + + + + + + + + + pg_get_acl + + pg_get_acl ( classid oid, objid oid, objsubid integer ) + aclitem[] + + + Returns the ACL for a database object, specified + by catalog OID, object OID and sub-object ID. This function returns + NULL values for undefined objects. + + + + + + + pg_describe_object + + pg_describe_object ( classid oid, objid oid, objsubid integer ) + text + + + Returns a textual description of a database object identified by + catalog OID, object OID, and sub-object ID (such as a column number + within a table; the sub-object ID is zero when referring to a whole + object). This description is intended to be human-readable, and might + be translated, depending on server configuration. This is especially + useful to determine the identity of an object referenced in the + pg_depend catalog. This function returns + NULL values for undefined objects. + + + + + + + pg_identify_object + + pg_identify_object ( classid oid, objid oid, objsubid integer ) + record + ( type text, + schema text, + name text, + identity text ) + + + Returns a row containing enough information to uniquely identify the + database object specified by catalog OID, object OID and sub-object + ID. + This information is intended to be machine-readable, and is never + translated. + type identifies the type of database object; + schema is the schema name that the object + belongs in, or NULL for object types that do not + belong to schemas; + name is the name of the object, quoted if + necessary, if the name (along with schema name, if pertinent) is + sufficient to uniquely identify the object, + otherwise NULL; + identity is the complete object identity, with + the precise format depending on object type, and each name within the + format being schema-qualified and quoted as necessary. Undefined + objects are identified with NULL values. + + + + + + + pg_identify_object_as_address + + pg_identify_object_as_address ( classid oid, objid oid, objsubid integer ) + record + ( type text, + object_names text[], + object_args text[] ) + + + Returns a row containing enough information to uniquely identify the + database object specified by catalog OID, object OID and sub-object + ID. + The returned information is independent of the current server, that + is, it could be used to identify an identically named object in + another server. + type identifies the type of database object; + object_names and + object_args + are text arrays that together form a reference to the object. + These three values can be passed + to pg_get_object_address to obtain the internal + address of the object. + + + + + + + pg_get_object_address + + pg_get_object_address ( type text, object_names text[], object_args text[] ) + record + ( classid oid, + objid oid, + objsubid integer ) + + + Returns a row containing enough information to uniquely identify the + database object specified by a type code and object name and argument + arrays. + The returned values are the ones that would be used in system catalogs + such as pg_depend; they can be passed to + other system functions such as pg_describe_object + or pg_identify_object. + classid is the OID of the system catalog + containing the object; + objid is the OID of the object itself, and + objsubid is the sub-object ID, or zero if none. + This function is the inverse + of pg_identify_object_as_address. + Undefined objects are identified with NULL values. + + + + +

+ + + pg_get_acl is useful for retrieving and inspecting + the privileges associated with database objects without looking at + specific catalogs. For example, to retrieve all the granted privileges + on objects in the current database: + +postgres=# SELECT + (pg_identify_object(s.classid,s.objid,s.objsubid)).*, + pg_catalog.pg_get_acl(s.classid,s.objid,s.objsubid) AS acl +FROM pg_catalog.pg_shdepend AS s +JOIN pg_catalog.pg_database AS d + ON d.datname = current_database() AND + d.oid = s.dbid +JOIN pg_catalog.pg_authid AS a + ON a.oid = s.refobjid AND + s.refclassid = 'pg_authid'::regclass +WHERE s.deptype = 'a'; +-[ RECORD 1 ]----------------------------------------- +type | table +schema | public +name | testtab +identity | public.testtab +acl | {postgres=arwdDxtm/postgres,foo=r/postgres} + + + + + + + Comment Information Functions + + + comment + about database objects + + + + The functions shown in + extract comments previously stored with the + command. A null value is returned if no + comment could be found for the specified parameters. + + + + Comment Information Functions + + + + + Function + + + Description + + + + + + + + + col_description + + col_description ( table oid, column integer ) + text + + + Returns the comment for a table column, which is specified by the OID + of its table and its column number. + (obj_description cannot be used for table + columns, since columns do not have OIDs of their own.) + + + + + + + obj_description + + obj_description ( object oid, catalog name ) + text + + + Returns the comment for a database object specified by its OID and the + name of the containing system catalog. For + example, obj_description(123456, 'pg_class') would + retrieve the comment for the table with OID 123456. + + + + + + obj_description ( object oid ) + text + + + Returns the comment for a database object specified by its OID alone. + This is deprecated since there is no guarantee + that OIDs are unique across different system catalogs; therefore, the + wrong comment might be returned. + + + + + + + shobj_description + + shobj_description ( object oid, catalog name ) + text + + + Returns the comment for a shared database object specified by its OID + and the name of the containing system catalog. This is just + like obj_description except that it is used for + retrieving comments on shared objects (that is, databases, roles, and + tablespaces). Some system catalogs are global to all databases within + each cluster, and the descriptions for objects in them are stored + globally as well. + + + + +

+ + + + + Data Validity Checking Functions + + + The functions shown in + can be helpful for checking validity of proposed input data. + + + + Data Validity Checking Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + pg_input_is_valid + + pg_input_is_valid ( + string text, + type text + ) + boolean + + + Tests whether the given string is valid + input for the specified data type, returning true or false. + + + This function will only work as desired if the data type's input + function has been updated to report invalid input as + a soft error. Otherwise, invalid input will abort + the transaction, just as if the string had been cast to the type + directly. + + + pg_input_is_valid('42', 'integer') + t + + + pg_input_is_valid('42000000000', 'integer') + f + + + pg_input_is_valid('1234.567', 'numeric(7,4)') + f + + + + + + pg_input_error_info + + pg_input_error_info ( + string text, + type text + ) + record + ( message text, + detail text, + hint text, + sql_error_code text ) + + + Tests whether the given string is valid + input for the specified data type; if not, return the details of + the error that would have been thrown. If the input is valid, the + results are NULL. The inputs are the same as + for pg_input_is_valid. + + + This function will only work as desired if the data type's input + function has been updated to report invalid input as + a soft error. Otherwise, invalid input will abort + the transaction, just as if the string had been cast to the type + directly. + + + SELECT * FROM pg_input_error_info('42000000000', 'integer') + + + message | detail | hint | sql_error_code +------------------------------------------------------+--------+------+---------------- + value "42000000000" is out of range for type integer | | | 22003 + + + + + +

+ + + + + Transaction ID and Snapshot Information Functions + + + The functions shown in + provide server transaction information in an exportable form. The main + use of these functions is to determine which transactions were committed + between two snapshots. + + + + Transaction ID and Snapshot Information Functions + + + + + Function + + + Description + + + + + + + + + age + + age ( xid ) + integer + + + Returns the number of transactions between the supplied + transaction id and the current transaction counter. + + + + + + + mxid_age + + mxid_age ( xid ) + integer + + + Returns the number of multixacts IDs between the supplied + multixact ID and the current multixacts counter. + + + + + + + pg_current_xact_id + + pg_current_xact_id () + xid8 + + + Returns the current transaction's ID. It will assign a new one if the + current transaction does not have one already (because it has not + performed any database updates); see for details. If executed in a + subtransaction, this will return the top-level transaction ID; + see for details. + + + + + + + pg_current_xact_id_if_assigned + + pg_current_xact_id_if_assigned () + xid8 + + + Returns the current transaction's ID, or NULL if no + ID is assigned yet. (It's best to use this variant if the transaction + might otherwise be read-only, to avoid unnecessary consumption of an + XID.) + If executed in a subtransaction, this will return the top-level + transaction ID. + + + + + + + pg_xact_status + + pg_xact_status ( xid8 ) + text + + + Reports the commit status of a recent transaction. + The result is one of in progress, + committed, or aborted, + provided that the transaction is recent enough that the system retains + the commit status of that transaction. + If it is old enough that no references to the transaction survive in + the system and the commit status information has been discarded, the + result is NULL. + Applications might use this function, for example, to determine + whether their transaction committed or aborted after the application + and database server become disconnected while + a COMMIT is in progress. + Note that prepared transactions are reported as in + progress; applications must check pg_prepared_xacts + if they need to determine whether a transaction ID belongs to a + prepared transaction. + + + + + + + pg_current_snapshot + + pg_current_snapshot () + pg_snapshot + + + Returns a current snapshot, a data structure + showing which transaction IDs are now in-progress. + Only top-level transaction IDs are included in the snapshot; + subtransaction IDs are not shown; see + for details. + + + + + + + pg_snapshot_xip + + pg_snapshot_xip ( pg_snapshot ) + setof xid8 + + + Returns the set of in-progress transaction IDs contained in a snapshot. + + + + + + + pg_snapshot_xmax + + pg_snapshot_xmax ( pg_snapshot ) + xid8 + + + Returns the xmax of a snapshot. + + + + + + + pg_snapshot_xmin + + pg_snapshot_xmin ( pg_snapshot ) + xid8 + + + Returns the xmin of a snapshot. + + + + + + + pg_visible_in_snapshot + + pg_visible_in_snapshot ( xid8, pg_snapshot ) + boolean + + + Is the given transaction ID visible according + to this snapshot (that is, was it completed before the snapshot was + taken)? Note that this function will not give the correct answer for + a subtransaction ID (subxid); see for + details. + + + + + + + pg_get_multixact_members + + pg_get_multixact_members ( multixid xid ) + setof record + ( xid xid, + mode text ) + + + Returns the transaction ID and lock mode for each member of the + specified multixact ID. The lock modes forupd, + fornokeyupd, sh, and + keysh correspond to the row-level locks + FOR UPDATE, FOR NO KEY UPDATE, + FOR SHARE, and FOR KEY SHARE, + respectively, as described in . Two + additional modes are specific to multixacts: + nokeyupd, used by updates that do not modify key + columns, and upd, used by updates or deletes that + modify key columns. + + + + +

+ + + The internal transaction ID type xid is 32 bits wide and + wraps around every 4 billion transactions. However, + the functions shown in , except + age, mxid_age, and + pg_get_multixact_members, use a + 64-bit type xid8 that does not wrap around during the life + of an installation and can be converted to xid by casting if + required; see for details. + The data type pg_snapshot stores information about + transaction ID visibility at a particular moment in time. Its components + are described in . + pg_snapshot's textual representation is + xmin:xmax:xip_list. + For example 10:20:10,14,15 means + xmin=10, xmax=20, xip_list=10, 14, 15. + + + + Snapshot Components + + + + Name + Description + + + + + + xmin + + Lowest transaction ID that was still active. All transaction IDs + less than xmin are either committed and visible, + or rolled back and dead. + + + + + xmax + + One past the highest completed transaction ID. All transaction IDs + greater than or equal to xmax had not yet + completed as of the time of the snapshot, and thus are invisible. + + + + + xip_list + + Transactions in progress at the time of the snapshot. A transaction + ID that is xmin <= X < + xmax and not in this list was already completed at the time + of the snapshot, and thus is either visible or dead according to its + commit status. This list does not include the transaction IDs of + subtransactions (subxids). + + + + +

+ + + In releases of PostgreSQL before 13 there was + no xid8 type, so variants of these functions were provided + that used bigint to represent a 64-bit XID, with a + correspondingly distinct snapshot data type txid_snapshot. + These older functions have txid in their names. They + are still supported for backward compatibility, but may be removed from a + future release. See . + + + + Deprecated Transaction ID and Snapshot Information Functions + + + + + Function + + + Description + + + + + + + + + + txid_current + + txid_current () + bigint + + + See pg_current_xact_id(). + + + + + + + txid_current_if_assigned + + txid_current_if_assigned () + bigint + + + See pg_current_xact_id_if_assigned(). + + + + + + + txid_current_snapshot + + txid_current_snapshot () + txid_snapshot + + + See pg_current_snapshot(). + + + + + + + txid_snapshot_xip + + txid_snapshot_xip ( txid_snapshot ) + setof bigint + + + See pg_snapshot_xip(). + + + + + + + txid_snapshot_xmax + + txid_snapshot_xmax ( txid_snapshot ) + bigint + + + See pg_snapshot_xmax(). + + + + + + + txid_snapshot_xmin + + txid_snapshot_xmin ( txid_snapshot ) + bigint + + + See pg_snapshot_xmin(). + + + + + + + txid_visible_in_snapshot + + txid_visible_in_snapshot ( bigint, txid_snapshot ) + boolean + + + See pg_visible_in_snapshot(). + + + + + + + txid_status + + txid_status ( bigint ) + text + + + See pg_xact_status(). + + + + +

+ + + + + Committed Transaction Information Functions + + + The functions shown in + provide information about when past transactions were committed. + They only provide useful data when the + configuration option is + enabled, and only for transactions that were committed after it was + enabled. Commit timestamp information is routinely removed during + vacuum. + + + + Committed Transaction Information Functions + + + + + Function + + + Description + + + + + + + + + pg_xact_commit_timestamp + + pg_xact_commit_timestamp ( xid ) + timestamp with time zone + + + Returns the commit timestamp of a transaction. + + + + + + + pg_xact_commit_timestamp_origin + + pg_xact_commit_timestamp_origin ( xid ) + record + ( timestamp timestamp with time zone, + roident oid) + + + Returns the commit timestamp and replication origin of a transaction. + + + + + + + pg_last_committed_xact + + pg_last_committed_xact () + record + ( xid xid, + timestamp timestamp with time zone, + roident oid ) + + + Returns the transaction ID, commit timestamp and replication origin + of the latest committed transaction. + + + + +

+ + + + + Control Data Functions + + + The functions shown in + print information initialized during initdb, such + as the catalog version. They also show information about write-ahead + logging and checkpoint processing. This information is cluster-wide, + not specific to any one database. These functions provide most of the same + information, from the same source, as the + application. + + + + Control Data Functions + + + + + Function + + + Description + + + + + + + + + pg_control_checkpoint + + pg_control_checkpoint () + record + + + Returns information about current checkpoint state, as shown in + . + + + + + + + pg_control_system + + pg_control_system () + record + + + Returns information about current control file state, as shown in + . + + + + + + + pg_control_init + + pg_control_init () + record + + + Returns information about cluster initialization state, as shown in + . + + + + + + + pg_control_recovery + + pg_control_recovery () + record + + + Returns information about recovery state, as shown in + . + + + + +

+ + + <function>pg_control_checkpoint</function> Output Columns + + + + Column Name + Data Type + + + + + + + checkpoint_lsn + pg_lsn + + + + redo_lsn + pg_lsn + + + + redo_wal_file + text + + + + timeline_id + integer + + + + prev_timeline_id + integer + + + + full_page_writes + boolean + + + + next_xid + text + + + + next_oid + oid + + + + next_multixact_id + xid + + + + next_multi_offset + xid + + + + oldest_xid + xid + + + + oldest_xid_dbid + oid + + + + oldest_active_xid + xid + + + + oldest_multi_xid + xid + + + + oldest_multi_dbid + oid + + + + oldest_commit_ts_xid + xid + + + + newest_commit_ts_xid + xid + + + + checkpoint_time + timestamp with time zone + + + + +

+ + + <function>pg_control_system</function> Output Columns + + + + Column Name + Data Type + + + + + + + pg_control_version + integer + + + + catalog_version_no + integer + + + + system_identifier + bigint + + + + pg_control_last_modified + timestamp with time zone + + + + +

+ + + <function>pg_control_init</function> Output Columns + + + + Column Name + Data Type + + + + + + + max_data_alignment + integer + + + + database_block_size + integer + + + + blocks_per_segment + integer + + + + wal_block_size + integer + + + + bytes_per_wal_segment + integer + + + + max_identifier_length + integer + + + + max_index_columns + integer + + + + max_toast_chunk_size + integer + + + + large_object_chunk_size + integer + + + + float8_pass_by_value + boolean + + + + data_page_checksum_version + integer + + + + default_char_signedness + boolean + + + + +

+ + + <function>pg_control_recovery</function> Output Columns + + + + Column Name + Data Type + + + + + + + min_recovery_end_lsn + pg_lsn + + + + min_recovery_end_timeline + integer + + + + backup_start_lsn + pg_lsn + + + + backup_end_lsn + pg_lsn + + + + end_of_backup_record_required + boolean + + + + +

+ + + + + Version Information Functions + + + The functions shown in + print version information. + + + + Version Information Functions + + + + + Function + + + Description + + + + + + + + + version + + version () + text + + + Returns a string describing the PostgreSQL + server's version. You can also get this information from + , or for a machine-readable + version use . Software + developers should use server_version_num (available + since 8.2) or instead of + parsing the text version. + + + + + + + unicode_version + + unicode_version () + text + + + Returns a string representing the version of Unicode used by + PostgreSQL. + + + + + + icu_unicode_version + + icu_unicode_version () + text + + + Returns a string representing the version of Unicode used by ICU, if + the server was built with ICU support; otherwise returns + NULL + + + +

+ + + + + WAL Summarization Information Functions + + + The functions shown in + print information about the status of WAL summarization. + See . + + + + WAL Summarization Information Functions + + + + + Function + + + Description + + + + + + + + + pg_available_wal_summaries + + pg_available_wal_summaries () + setof record + ( tli bigint, + start_lsn pg_lsn, + end_lsn pg_lsn ) + + + Returns information about the WAL summary files present in the + data directory, under pg_wal/summaries. + One row will be returned per WAL summary file. Each file summarizes + WAL on the indicated TLI within the indicated LSN range. This function + might be useful to determine whether enough WAL summaries are present + on the server to take an incremental backup based on some prior + backup whose start LSN is known. + + + + + + + pg_wal_summary_contents + + pg_wal_summary_contents ( tli bigint, start_lsn pg_lsn, end_lsn pg_lsn ) + setof record + ( relfilenode oid, + reltablespace oid, + reldatabase oid, + relforknumber smallint, + relblocknumber bigint, + is_limit_block boolean ) + + + Returns one information about the contents of a single WAL summary file + identified by TLI and starting and ending LSNs. Each row with + is_limit_block false indicates that the block + identified by the remaining output columns was modified by at least + one WAL record within the range of records summarized by this file. + Each row with is_limit_block true indicates either + that (a) the relation fork was truncated to the length given by + relblocknumber within the relevant range of WAL + records or (b) that the relation fork was created or dropped within + the relevant range of WAL records; in such cases, + relblocknumber will be zero. + + + + + + + pg_get_wal_summarizer_state + + pg_get_wal_summarizer_state () + record + ( summarized_tli bigint, + summarized_lsn pg_lsn, + pending_lsn pg_lsn, + summarizer_pid int ) + + + Returns information about the progress of the WAL summarizer. If the + WAL summarizer has never run since the instance was started, then + summarized_tli and summarized_lsn + will be 0 and 0/00000000 respectively; + otherwise, they will be the TLI and ending LSN of the last WAL summary + file written to disk. If the WAL summarizer is currently running, + pending_lsn will be the ending LSN of the last + record that it has consumed, which must always be greater than or + equal to summarized_lsn; if the WAL summarizer is + not running, it will be equal to summarized_lsn. + summarizer_pid is the PID of the WAL summarizer + process, if it is running, and otherwise NULL. + + + As a special exception, the WAL summarizer will refuse to generate + WAL summary files if run on WAL generated under + wal_level=minimal, since such summaries would be + unsafe to use as the basis for an incremental backup. In this case, + the fields above will continue to advance as if summaries were being + generated, but nothing will be written to disk. Once the summarizer + reaches WAL generated while wal_level was set + to replica or higher, it will resume writing + summaries to disk. + + + + +

+ + + + diff --git a/doc/src/sgml/func/func-json.sgml b/doc/src/sgml/func/func-json.sgml new file mode 100644 index 00000000000..91f98a345d4 --- /dev/null +++ b/doc/src/sgml/func/func-json.sgml @@ -0,0 +1,3945 @@ + + JSON Functions and Operators + + + JSON + functions and operators + + + SQL/JSON + functions and expressions + + + + This section describes: + + + + + functions and operators for processing and creating JSON data + + + + + the SQL/JSON path language + + + + + the SQL/JSON query functions + + + + + + + To provide native support for JSON data types within the SQL environment, + PostgreSQL implements the + SQL/JSON data model. + This model comprises sequences of items. Each item can hold SQL scalar + values, with an additional SQL/JSON null value, and composite data structures + that use JSON arrays and objects. The model is a formalization of the implied + data model in the JSON specification + RFC 7159. + + + + SQL/JSON allows you to handle JSON data alongside regular SQL data, + with transaction support, including: + + + + + Uploading JSON data into the database and storing it in + regular SQL columns as character or binary strings. + + + + + Generating JSON objects and arrays from relational data. + + + + + Querying JSON data using SQL/JSON query functions and + SQL/JSON path language expressions. + + + + + + + To learn more about the SQL/JSON standard, see + . For details on JSON types + supported in PostgreSQL, + see . + + + + Processing and Creating JSON Data + + + shows the operators that + are available for use with JSON data types (see ). + In addition, the usual comparison operators shown in are available for + jsonb, though not for json. The comparison + operators follow the ordering rules for B-tree operations outlined in + . + See also for the aggregate + function json_agg which aggregates record + values as JSON, the aggregate function + json_object_agg which aggregates pairs of values + into a JSON object, and their jsonb equivalents, + jsonb_agg and jsonb_object_agg. + + + + <type>json</type> and <type>jsonb</type> Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + json -> integer + json + + + jsonb -> integer + jsonb + + + Extracts n'th element of JSON array + (array elements are indexed from zero, but negative integers count + from the end). + + + '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -> 2 + {"c":"baz"} + + + '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -> -3 + {"a":"foo"} + + + + + + json -> text + json + + + jsonb -> text + jsonb + + + Extracts JSON object field with the given key. + + + '{"a": {"b":"foo"}}'::json -> 'a' + {"b":"foo"} + + + + + + json ->> integer + text + + + jsonb ->> integer + text + + + Extracts n'th element of JSON array, + as text. + + + '[1,2,3]'::json ->> 2 + 3 + + + + + + json ->> text + text + + + jsonb ->> text + text + + + Extracts JSON object field with the given key, as text. + + + '{"a":1,"b":2}'::json ->> 'b' + 2 + + + + + + json #> text[] + json + + + jsonb #> text[] + jsonb + + + Extracts JSON sub-object at the specified path, where path elements + can be either field keys or array indexes. + + + '{"a": {"b": ["foo","bar"]}}'::json #> '{a,b,1}' + "bar" + + + + + + json #>> text[] + text + + + jsonb #>> text[] + text + + + Extracts JSON sub-object at the specified path as text. + + + '{"a": {"b": ["foo","bar"]}}'::json #>> '{a,b,1}' + bar + + + + +

+ + + + The field/element/path extraction operators return NULL, rather than + failing, if the JSON input does not have the right structure to match + the request; for example if no such key or array element exists. + + + + + Some further operators exist only for jsonb, as shown + in . + + describes how these operators can be used to effectively search indexed + jsonb data. + + + + Additional <type>jsonb</type> Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + jsonb @> jsonb + boolean + + + Does the first JSON value contain the second? + (See for details about containment.) + + + '{"a":1, "b":2}'::jsonb @> '{"b":2}'::jsonb + t + + + + + + jsonb <@ jsonb + boolean + + + Is the first JSON value contained in the second? + + + '{"b":2}'::jsonb <@ '{"a":1, "b":2}'::jsonb + t + + + + + + jsonb ? text + boolean + + + Does the text string exist as a top-level key or array element within + the JSON value? + + + '{"a":1, "b":2}'::jsonb ? 'b' + t + + + '["a", "b", "c"]'::jsonb ? 'b' + t + + + + + + jsonb ?| text[] + boolean + + + Do any of the strings in the text array exist as top-level keys or + array elements? + + + '{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'd'] + t + + + + + + jsonb ?& text[] + boolean + + + Do all of the strings in the text array exist as top-level keys or + array elements? + + + '["a", "b", "c"]'::jsonb ?& array['a', 'b'] + t + + + + + + jsonb || jsonb + jsonb + + + Concatenates two jsonb values. + Concatenating two arrays generates an array containing all the + elements of each input. Concatenating two objects generates an + object containing the union of their + keys, taking the second object's value when there are duplicate keys. + All other cases are treated by converting a non-array input into a + single-element array, and then proceeding as for two arrays. + Does not operate recursively: only the top-level array or object + structure is merged. + + + '["a", "b"]'::jsonb || '["a", "d"]'::jsonb + ["a", "b", "a", "d"] + + + '{"a": "b"}'::jsonb || '{"c": "d"}'::jsonb + {"a": "b", "c": "d"} + + + '[1, 2]'::jsonb || '3'::jsonb + [1, 2, 3] + + + '{"a": "b"}'::jsonb || '42'::jsonb + [{"a": "b"}, 42] + + + To append an array to another array as a single entry, wrap it + in an additional layer of array, for example: + + + '[1, 2]'::jsonb || jsonb_build_array('[3, 4]'::jsonb) + [1, 2, [3, 4]] + + + + + + jsonb - text + jsonb + + + Deletes a key (and its value) from a JSON object, or matching string + value(s) from a JSON array. + + + '{"a": "b", "c": "d"}'::jsonb - 'a' + {"c": "d"} + + + '["a", "b", "c", "b"]'::jsonb - 'b' + ["a", "c"] + + + + + + jsonb - text[] + jsonb + + + Deletes all matching keys or array elements from the left operand. + + + '{"a": "b", "c": "d"}'::jsonb - '{a,c}'::text[] + {} + + + + + + jsonb - integer + jsonb + + + Deletes the array element with specified index (negative + integers count from the end). Throws an error if JSON value + is not an array. + + + '["a", "b"]'::jsonb - 1 + ["a"] + + + + + + jsonb #- text[] + jsonb + + + Deletes the field or array element at the specified path, where path + elements can be either field keys or array indexes. + + + '["a", {"b":1}]'::jsonb #- '{1,b}' + ["a", {}] + + + + + + jsonb @? jsonpath + boolean + + + Does JSON path return any item for the specified JSON value? + (This is useful only with SQL-standard JSON path expressions, not + predicate check + expressions, since those always return a value.) + + + '{"a":[1,2,3,4,5]}'::jsonb @? '$.a[*] ? (@ > 2)' + t + + + + + + jsonb @@ jsonpath + boolean + + + Returns the result of a JSON path predicate check for the + specified JSON value. + (This is useful only + with predicate + check expressions, not SQL-standard JSON path expressions, + since it will return NULL if the path result is + not a single boolean value.) + + + '{"a":[1,2,3,4,5]}'::jsonb @@ '$.a[*] > 2' + t + + + + +

+ + + + The jsonpath operators @? + and @@ suppress the following errors: missing object + field or array element, unexpected JSON item type, datetime and numeric + errors. The jsonpath-related functions described below can + also be told to suppress these types of errors. This behavior might be + helpful when searching JSON document collections of varying structure. + + + + + shows the functions that are + available for constructing json and jsonb values. + Some functions in this table have a RETURNING clause, + which specifies the data type returned. It must be one of json, + jsonb, bytea, a character string type (text, + char, or varchar), or a type + that can be cast to json. + By default, the json type is returned. + + + + JSON Creation Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + to_json + + to_json ( anyelement ) + json + + + + to_jsonb + + to_jsonb ( anyelement ) + jsonb + + + Converts any SQL value to json or jsonb. + Arrays and composites are converted recursively to arrays and + objects (multidimensional arrays become arrays of arrays in JSON). + Otherwise, if there is a cast from the SQL data type + to json, the cast function will be used to perform the + conversion; + + For example, the extension has a cast + from hstore to json, so that + hstore values converted via the JSON creation functions + will be represented as JSON objects, not as primitive string values. + + + otherwise, a scalar JSON value is produced. For any scalar other than + a number, a Boolean, or a null value, the text representation will be + used, with escaping as necessary to make it a valid JSON string value. + + + to_json('Fred said "Hi."'::text) + "Fred said \"Hi.\"" + + + to_jsonb(row(42, 'Fred said "Hi."'::text)) + {"f1": 42, "f2": "Fred said \"Hi.\""} + + + + + + + array_to_json + + array_to_json ( anyarray , boolean ) + json + + + Converts an SQL array to a JSON array. The behavior is the same + as to_json except that line feeds will be added + between top-level array elements if the optional boolean parameter is + true. + + + array_to_json('{{1,5},{99,100}}'::int[]) + [[1,5],[99,100]] + + + + + + + json_array + json_array ( + { value_expression FORMAT JSON } , ... + { NULL | ABSENT } ON NULL + RETURNING data_type FORMAT JSON ENCODING UTF8 ) + + + json_array ( + query_expression + RETURNING data_type FORMAT JSON ENCODING UTF8 ) + + + Constructs a JSON array from either a series of + value_expression parameters or from the results + of query_expression, + which must be a SELECT query returning a single column. If + ABSENT ON NULL is specified, NULL values are ignored. + This is always the case if a + query_expression is used. + + + json_array(1,true,json '{"a":null}') + [1, true, {"a":null}] + + + json_array(SELECT * FROM (VALUES(1),(2)) t) + [1, 2] + + + + + + + row_to_json + + row_to_json ( record , boolean ) + json + + + Converts an SQL composite value to a JSON object. The behavior is the + same as to_json except that line feeds will be + added between top-level elements if the optional boolean parameter is + true. + + + row_to_json(row(1,'foo')) + {"f1":1,"f2":"foo"} + + + + + + + json_build_array + + json_build_array ( VARIADIC "any" ) + json + + + + jsonb_build_array + + jsonb_build_array ( VARIADIC "any" ) + jsonb + + + Builds a possibly-heterogeneously-typed JSON array out of a variadic + argument list. Each argument is converted as + per to_json or to_jsonb. + + + json_build_array(1, 2, 'foo', 4, 5) + [1, 2, "foo", 4, 5] + + + + + + + json_build_object + + json_build_object ( VARIADIC "any" ) + json + + + + jsonb_build_object + + jsonb_build_object ( VARIADIC "any" ) + jsonb + + + Builds a JSON object out of a variadic argument list. By convention, + the argument list consists of alternating keys and values. Key + arguments are coerced to text; value arguments are converted as + per to_json or to_jsonb. + + + json_build_object('foo', 1, 2, row(3,'bar')) + {"foo" : 1, "2" : {"f1":3,"f2":"bar"}} + + + + + + json_object + json_object ( + { key_expression { VALUE | ':' } + value_expression FORMAT JSON ENCODING UTF8 }, ... + { NULL | ABSENT } ON NULL + { WITH | WITHOUT } UNIQUE KEYS + RETURNING data_type FORMAT JSON ENCODING UTF8 ) + + + Constructs a JSON object of all the key/value pairs given, + or an empty object if none are given. + key_expression is a scalar expression + defining the JSON key, which is + converted to the text type. + It cannot be NULL nor can it + belong to a type that has a cast to the json type. + If WITH UNIQUE KEYS is specified, there must not + be any duplicate key_expression. + Any pair for which the value_expression + evaluates to NULL is omitted from the output + if ABSENT ON NULL is specified; + if NULL ON NULL is specified or the clause + omitted, the key is included with value NULL. + + + json_object('code' VALUE 'P123', 'title': 'Jaws') + {"code" : "P123", "title" : "Jaws"} + + + + + + + json_object + + json_object ( text[] ) + json + + + + jsonb_object + + jsonb_object ( text[] ) + jsonb + + + Builds a JSON object out of a text array. The array must have either + exactly one dimension with an even number of members, in which case + they are taken as alternating key/value pairs, or two dimensions + such that each inner array has exactly two elements, which + are taken as a key/value pair. All values are converted to JSON + strings. + + + json_object('{a, 1, b, "def", c, 3.5}') + {"a" : "1", "b" : "def", "c" : "3.5"} + + json_object('{{a, 1}, {b, "def"}, {c, 3.5}}') + {"a" : "1", "b" : "def", "c" : "3.5"} + + + + + + json_object ( keys text[], values text[] ) + json + + + jsonb_object ( keys text[], values text[] ) + jsonb + + + This form of json_object takes keys and values + pairwise from separate text arrays. Otherwise it is identical to + the one-argument form. + + + json_object('{a,b}', '{1,2}') + {"a": "1", "b": "2"} + + + + + + json constructor + json ( + expression + FORMAT JSON ENCODING UTF8 + { WITH | WITHOUT } UNIQUE KEYS ) + json + + + Converts a given expression specified as text or + bytea string (in UTF8 encoding) into a JSON + value. If expression is NULL, an + SQL null value is returned. + If WITH UNIQUE is specified, the + expression must not contain any duplicate + object keys. + + + json('{"a":123, "b":[true,"foo"], "a":"bar"}') + {"a":123, "b":[true,"foo"], "a":"bar"} + + + + + + + json_scalar + json_scalar ( expression ) + + + Converts a given SQL scalar value into a JSON scalar value. + If the input is NULL, an SQL null is returned. If + the input is number or a boolean value, a corresponding JSON number + or boolean value is returned. For any other value, a JSON string is + returned. + + + json_scalar(123.45) + 123.45 + + + json_scalar(CURRENT_TIMESTAMP) + "2022-05-10T10:51:04.62128-04:00" + + + + + + json_serialize ( + expression FORMAT JSON ENCODING UTF8 + RETURNING data_type FORMAT JSON ENCODING UTF8 ) + + + Converts an SQL/JSON expression into a character or binary string. The + expression can be of any JSON type, any + character string type, or bytea in UTF8 encoding. + The returned type used in RETURNING can be any + character string type or bytea. The default is + text. + + + json_serialize('{ "a" : 1 } ' RETURNING bytea) + \x7b20226122203a2031207d20 + + + + +

+ + + details SQL/JSON + facilities for testing JSON. + + + + SQL/JSON Testing Functions + + + + + Function signature + + + Description + + + Example(s) + + + + + + + IS JSON + expression IS NOT JSON + { VALUE | SCALAR | ARRAY | OBJECT } + { WITH | WITHOUT } UNIQUE KEYS + + + This predicate tests whether expression can be + parsed as JSON, possibly of a specified type. + If SCALAR or ARRAY or + OBJECT is specified, the + test is whether or not the JSON is of that particular type. If + WITH UNIQUE KEYS is specified, then any object in the + expression is also tested to see if it + has duplicate keys. + + + +SELECT js, + js IS JSON "json?", + js IS JSON SCALAR "scalar?", + js IS JSON OBJECT "object?", + js IS JSON ARRAY "array?" +FROM (VALUES + ('123'), ('"abc"'), ('{"a": "b"}'), ('[1,2]'),('abc')) foo(js); + js | json? | scalar? | object? | array? +------------+-------+---------+---------+-------- + 123 | t | t | f | f + "abc" | t | t | f | f + {"a": "b"} | t | f | t | f + [1,2] | t | f | f | t + abc | f | f | f | f + + + + +SELECT js, + js IS JSON OBJECT "object?", + js IS JSON ARRAY "array?", + js IS JSON ARRAY WITH UNIQUE KEYS "array w. UK?", + js IS JSON ARRAY WITHOUT UNIQUE KEYS "array w/o UK?" +FROM (VALUES ('[{"a":"1"}, + {"b":"2","b":"3"}]')) foo(js); +-[ RECORD 1 ]-+-------------------- +js | [{"a":"1"}, + + | {"b":"2","b":"3"}] +object? | f +array? | t +array w. UK? | f +array w/o UK? | t + + + + + +

+ + + shows the functions that + are available for processing json and jsonb values. + + + + JSON Processing Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + json_array_elements + + json_array_elements ( json ) + setof json + + + + jsonb_array_elements + + jsonb_array_elements ( jsonb ) + setof jsonb + + + Expands the top-level JSON array into a set of JSON values. + + + select * from json_array_elements('[1,true, [2,false]]') + + + value +----------- + 1 + true + [2,false] + + + + + + + + json_array_elements_text + + json_array_elements_text ( json ) + setof text + + + + jsonb_array_elements_text + + jsonb_array_elements_text ( jsonb ) + setof text + + + Expands the top-level JSON array into a set of text values. + + + select * from json_array_elements_text('["foo", "bar"]') + + + value +----------- + foo + bar + + + + + + + + json_array_length + + json_array_length ( json ) + integer + + + + jsonb_array_length + + jsonb_array_length ( jsonb ) + integer + + + Returns the number of elements in the top-level JSON array. + + + json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]') + 5 + + + jsonb_array_length('[]') + 0 + + + + + + + json_each + + json_each ( json ) + setof record + ( key text, + value json ) + + + + jsonb_each + + jsonb_each ( jsonb ) + setof record + ( key text, + value jsonb ) + + + Expands the top-level JSON object into a set of key/value pairs. + + + select * from json_each('{"a":"foo", "b":"bar"}') + + + key | value +-----+------- + a | "foo" + b | "bar" + + + + + + + + json_each_text + + json_each_text ( json ) + setof record + ( key text, + value text ) + + + + jsonb_each_text + + jsonb_each_text ( jsonb ) + setof record + ( key text, + value text ) + + + Expands the top-level JSON object into a set of key/value pairs. + The returned values will be of + type text. + + + select * from json_each_text('{"a":"foo", "b":"bar"}') + + + key | value +-----+------- + a | foo + b | bar + + + + + + + + json_extract_path + + json_extract_path ( from_json json, VARIADIC path_elems text[] ) + json + + + + jsonb_extract_path + + jsonb_extract_path ( from_json jsonb, VARIADIC path_elems text[] ) + jsonb + + + Extracts JSON sub-object at the specified path. + (This is functionally equivalent to the #> + operator, but writing the path out as a variadic list can be more + convenient in some cases.) + + + json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6') + "foo" + + + + + + + json_extract_path_text + + json_extract_path_text ( from_json json, VARIADIC path_elems text[] ) + text + + + + jsonb_extract_path_text + + jsonb_extract_path_text ( from_json jsonb, VARIADIC path_elems text[] ) + text + + + Extracts JSON sub-object at the specified path as text. + (This is functionally equivalent to the #>> + operator.) + + + json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6') + foo + + + + + + + json_object_keys + + json_object_keys ( json ) + setof text + + + + jsonb_object_keys + + jsonb_object_keys ( jsonb ) + setof text + + + Returns the set of keys in the top-level JSON object. + + + select * from json_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}}') + + + json_object_keys +------------------ + f1 + f2 + + + + + + + + json_populate_record + + json_populate_record ( base anyelement, from_json json ) + anyelement + + + + jsonb_populate_record + + jsonb_populate_record ( base anyelement, from_json jsonb ) + anyelement + + + Expands the top-level JSON object to a row having the composite type + of the base argument. The JSON object + is scanned for fields whose names match column names of the output row + type, and their values are inserted into those columns of the output. + (Fields that do not correspond to any output column name are ignored.) + In typical use, the value of base is just + NULL, which means that any output columns that do + not match any object field will be filled with nulls. However, + if base isn't NULL then + the values it contains will be used for unmatched columns. + + + To convert a JSON value to the SQL type of an output column, the + following rules are applied in sequence: + + + + A JSON null value is converted to an SQL null in all cases. + + + + + If the output column is of type json + or jsonb, the JSON value is just reproduced exactly. + + + + + If the output column is a composite (row) type, and the JSON value + is a JSON object, the fields of the object are converted to columns + of the output row type by recursive application of these rules. + + + + + Likewise, if the output column is an array type and the JSON value + is a JSON array, the elements of the JSON array are converted to + elements of the output array by recursive application of these + rules. + + + + + Otherwise, if the JSON value is a string, the contents of the + string are fed to the input conversion function for the column's + data type. + + + + + Otherwise, the ordinary text representation of the JSON value is + fed to the input conversion function for the column's data type. + + + + + + While the example below uses a constant JSON value, typical use would + be to reference a json or jsonb column + laterally from another table in the query's FROM + clause. Writing json_populate_record in + the FROM clause is good practice, since all of the + extracted columns are available for use without duplicate function + calls. + + + create type subrowtype as (d int, e text); + create type myrowtype as (a int, b text[], c subrowtype); + + + select * from json_populate_record(null::myrowtype, + '{"a": 1, "b": ["2", "a b"], "c": {"d": 4, "e": "a b c"}, "x": "foo"}') + + + a | b | c +---+-----------+------------- + 1 | {2,"a b"} | (4,"a b c") + + + + + + + + jsonb_populate_record_valid + + jsonb_populate_record_valid ( base anyelement, from_json json ) + boolean + + + Function for testing jsonb_populate_record. Returns + true if the input jsonb_populate_record + would finish without an error for the given input JSON object; that is, it's + valid input, false otherwise. + + + create type jsb_char2 as (a char(2)); + + + select jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aaa"}'); + + + jsonb_populate_record_valid +----------------------------- + f +(1 row) + + + select * from jsonb_populate_record(NULL::jsb_char2, '{"a": "aaa"}') q; + + +ERROR: value too long for type character(2) + + select jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aa"}'); + + + jsonb_populate_record_valid +----------------------------- + t +(1 row) + + + select * from jsonb_populate_record(NULL::jsb_char2, '{"a": "aa"}') q; + + + a +---- + aa +(1 row) + + + + + + + + json_populate_recordset + + json_populate_recordset ( base anyelement, from_json json ) + setof anyelement + + + + jsonb_populate_recordset + + jsonb_populate_recordset ( base anyelement, from_json jsonb ) + setof anyelement + + + Expands the top-level JSON array of objects to a set of rows having + the composite type of the base argument. + Each element of the JSON array is processed as described above + for json[b]_populate_record. + + + create type twoints as (a int, b int); + + + select * from json_populate_recordset(null::twoints, '[{"a":1,"b":2}, {"a":3,"b":4}]') + + + a | b +---+--- + 1 | 2 + 3 | 4 + + + + + + + + json_to_record + + json_to_record ( json ) + record + + + + jsonb_to_record + + jsonb_to_record ( jsonb ) + record + + + Expands the top-level JSON object to a row having the composite type + defined by an AS clause. (As with all functions + returning record, the calling query must explicitly + define the structure of the record with an AS + clause.) The output record is filled from fields of the JSON object, + in the same way as described above + for json[b]_populate_record. Since there is no + input record value, unmatched columns are always filled with nulls. + + + create type myrowtype as (a int, b text); + + + select * from json_to_record('{"a":1,"b":[1,2,3],"c":[1,2,3],"e":"bar","r": {"a": 123, "b": "a b c"}}') as x(a int, b text, c int[], d text, r myrowtype) + + + a | b | c | d | r +---+---------+---------+---+--------------- + 1 | [1,2,3] | {1,2,3} | | (123,"a b c") + + + + + + + + json_to_recordset + + json_to_recordset ( json ) + setof record + + + + jsonb_to_recordset + + jsonb_to_recordset ( jsonb ) + setof record + + + Expands the top-level JSON array of objects to a set of rows having + the composite type defined by an AS clause. (As + with all functions returning record, the calling query + must explicitly define the structure of the record with + an AS clause.) Each element of the JSON array is + processed as described above + for json[b]_populate_record. + + + select * from json_to_recordset('[{"a":1,"b":"foo"}, {"a":"2","c":"bar"}]') as x(a int, b text) + + + a | b +---+----- + 1 | foo + 2 | + + + + + + + + jsonb_set + + jsonb_set ( target jsonb, path text[], new_value jsonb , create_if_missing boolean ) + jsonb + + + Returns target + with the item designated by path + replaced by new_value, or with + new_value added if + create_if_missing is true (which is the + default) and the item designated by path + does not exist. + All earlier steps in the path must exist, or + the target is returned unchanged. + As with the path oriented operators, negative integers that + appear in the path count from the end + of JSON arrays. + If the last path step is an array index that is out of range, + and create_if_missing is true, the new + value is added at the beginning of the array if the index is negative, + or at the end of the array if it is positive. + + + jsonb_set('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', '[2,3,4]', false) + [{"f1": [2, 3, 4], "f2": null}, 2, null, 3] + + + jsonb_set('[{"f1":1,"f2":null},2]', '{0,f3}', '[2,3,4]') + [{"f1": 1, "f2": null, "f3": [2, 3, 4]}, 2] + + + + + + + jsonb_set_lax + + jsonb_set_lax ( target jsonb, path text[], new_value jsonb , create_if_missing boolean , null_value_treatment text ) + jsonb + + + If new_value is not NULL, + behaves identically to jsonb_set. Otherwise behaves + according to the value + of null_value_treatment which must be one + of 'raise_exception', + 'use_json_null', 'delete_key', or + 'return_target'. The default is + 'use_json_null'. + + + jsonb_set_lax('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', null) + [{"f1": null, "f2": null}, 2, null, 3] + + + jsonb_set_lax('[{"f1":99,"f2":null},2]', '{0,f3}', null, true, 'return_target') + [{"f1": 99, "f2": null}, 2] + + + + + + + jsonb_insert + + jsonb_insert ( target jsonb, path text[], new_value jsonb , insert_after boolean ) + jsonb + + + Returns target + with new_value inserted. If the item + designated by the path is an array + element, new_value will be inserted before + that item if insert_after is false (which + is the default), or after it + if insert_after is true. If the item + designated by the path is an object + field, new_value will be inserted only if + the object does not already contain that key. + All earlier steps in the path must exist, or + the target is returned unchanged. + As with the path oriented operators, negative integers that + appear in the path count from the end + of JSON arrays. + If the last path step is an array index that is out of range, the new + value is added at the beginning of the array if the index is negative, + or at the end of the array if it is positive. + + + jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"') + {"a": [0, "new_value", 1, 2]} + + + jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"', true) + {"a": [0, 1, "new_value", 2]} + + + + + + + json_strip_nulls + + json_strip_nulls ( target json ,strip_in_arrays boolean ) + json + + + + jsonb_strip_nulls + + jsonb_strip_nulls ( target jsonb ,strip_in_arrays boolean ) + jsonb + + + Deletes all object fields that have null values from the given JSON + value, recursively. + If strip_in_arrays is true (the default is false), + null array elements are also stripped. + Otherwise they are not stripped. Bare null values are never stripped. + + + json_strip_nulls('[{"f1":1, "f2":null}, 2, null, 3]') + [{"f1":1},2,null,3] + + + jsonb_strip_nulls('[1,2,null,3,4]', true); + [1,2,3,4] + + + + + + + + jsonb_path_exists + + jsonb_path_exists ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + boolean + + + Checks whether the JSON path returns any item for the specified JSON + value. + (This is useful only with SQL-standard JSON path expressions, not + predicate check + expressions, since those always return a value.) + If the vars argument is specified, it must + be a JSON object, and its fields provide named values to be + substituted into the jsonpath expression. + If the silent argument is specified and + is true, the function suppresses the same errors + as the @? and @@ operators do. + + + jsonb_path_exists('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}') + t + + + + + + + jsonb_path_match + + jsonb_path_match ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + boolean + + + Returns the SQL boolean result of a JSON path predicate check + for the specified JSON value. + (This is useful only + with predicate + check expressions, not SQL-standard JSON path expressions, + since it will either fail or return NULL if the + path result is not a single boolean value.) + The optional vars + and silent arguments act the same as + for jsonb_path_exists. + + + jsonb_path_match('{"a":[1,2,3,4,5]}', 'exists($.a[*] ? (@ >= $min && @ <= $max))', '{"min":2, "max":4}') + t + + + + + + + jsonb_path_query + + jsonb_path_query ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + setof jsonb + + + Returns all JSON items returned by the JSON path for the specified + JSON value. + For SQL-standard JSON path expressions it returns the JSON + values selected from target. + For predicate + check expressions it returns the result of the predicate + check: true, false, + or null. + The optional vars + and silent arguments act the same as + for jsonb_path_exists. + + + select * from jsonb_path_query('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}') + + + jsonb_path_query +------------------ + 2 + 3 + 4 + + + + + + + + jsonb_path_query_array + + jsonb_path_query_array ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + jsonb + + + Returns all JSON items returned by the JSON path for the specified + JSON value, as a JSON array. + The parameters are the same as + for jsonb_path_query. + + + jsonb_path_query_array('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}') + [2, 3, 4] + + + + + + + jsonb_path_query_first + + jsonb_path_query_first ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + jsonb + + + Returns the first JSON item returned by the JSON path for the + specified JSON value, or NULL if there are no + results. + The parameters are the same as + for jsonb_path_query. + + + jsonb_path_query_first('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}') + 2 + + + + + + + jsonb_path_exists_tz + + jsonb_path_exists_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + boolean + + + + jsonb_path_match_tz + + jsonb_path_match_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + boolean + + + + jsonb_path_query_tz + + jsonb_path_query_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + setof jsonb + + + + jsonb_path_query_array_tz + + jsonb_path_query_array_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + jsonb + + + + jsonb_path_query_first_tz + + jsonb_path_query_first_tz ( target jsonb, path jsonpath , vars jsonb , silent boolean ) + jsonb + + + These functions act like their counterparts described above without + the _tz suffix, except that these functions support + comparisons of date/time values that require timezone-aware + conversions. The example below requires interpretation of the + date-only value 2015-08-02 as a timestamp with time + zone, so the result depends on the current + setting. Due to this dependency, these + functions are marked as stable, which means these functions cannot be + used in indexes. Their counterparts are immutable, and so can be used + in indexes; but they will throw errors if asked to make such + comparisons. + + + jsonb_path_exists_tz('["2015-08-01 12:00:00-05"]', '$[*] ? (@.datetime() < "2015-08-02".datetime())') + t + + + + + + + jsonb_pretty + + jsonb_pretty ( jsonb ) + text + + + Converts the given JSON value to pretty-printed, indented text. + + + jsonb_pretty('[{"f1":1,"f2":null}, 2]') + + +[ + { + "f1": 1, + "f2": null + }, + 2 +] + + + + + + + + json_typeof + + json_typeof ( json ) + text + + + + jsonb_typeof + + jsonb_typeof ( jsonb ) + text + + + Returns the type of the top-level JSON value as a text string. + Possible types are + object, array, + string, number, + boolean, and null. + (The null result should not be confused + with an SQL NULL; see the examples.) + + + json_typeof('-123.4') + number + + + json_typeof('null'::json) + null + + + json_typeof(NULL::json) IS NULL + t + + + + +

+ + + + The SQL/JSON Path Language + + + SQL/JSON path language + + + + SQL/JSON path expressions specify item(s) to be retrieved + from a JSON value, similarly to XPath expressions used + for access to XML content. In PostgreSQL, + path expressions are implemented as the jsonpath + data type and can use any elements described in + . + + + + JSON query functions and operators + pass the provided path expression to the path engine + for evaluation. If the expression matches the queried JSON data, + the corresponding JSON item, or set of items, is returned. + If there is no match, the result will be NULL, + false, or an error, depending on the function. + Path expressions are written in the SQL/JSON path language + and can include arithmetic expressions and functions. + + + + A path expression consists of a sequence of elements allowed + by the jsonpath data type. + The path expression is normally evaluated from left to right, but + you can use parentheses to change the order of operations. + If the evaluation is successful, a sequence of JSON items is produced, + and the evaluation result is returned to the JSON query function + that completes the specified computation. + + + + To refer to the JSON value being queried (the + context item), use the $ variable + in the path expression. The first element of a path must always + be $. It can be followed by one or more + accessor operators, + which go down the JSON structure level by level to retrieve sub-items + of the context item. Each accessor operator acts on the + result(s) of the previous evaluation step, producing zero, one, or more + output items from each input item. + + + + For example, suppose you have some JSON data from a GPS tracker that you + would like to parse, such as: + +SELECT '{ + "track": { + "segments": [ + { + "location": [ 47.763, 13.4034 ], + "start time": "2018-10-14 10:05:14", + "HR": 73 + }, + { + "location": [ 47.706, 13.2635 ], + "start time": "2018-10-14 10:39:21", + "HR": 135 + } + ] + } +}' AS json \gset + + (The above example can be copied-and-pasted + into psql to set things up for the following + examples. Then psql will + expand :'json' into a suitably-quoted string + constant containing the JSON value.) + + + + To retrieve the available track segments, you need to use the + .key accessor + operator to descend through surrounding JSON objects, for example: + +=> select jsonb_path_query(:'json', '$.track.segments'); + jsonb_path_query +-----------------------------------------------------------&zwsp;-----------------------------------------------------------&zwsp;--------------------------------------------- + [{"HR": 73, "location": [47.763, 13.4034], "start time": "2018-10-14 10:05:14"}, {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"}] + + + + + To retrieve the contents of an array, you typically use the + [*] operator. + The following example will return the location coordinates for all + the available track segments: + +=> select jsonb_path_query(:'json', '$.track.segments[*].location'); + jsonb_path_query +------------------- + [47.763, 13.4034] + [47.706, 13.2635] + + Here we started with the whole JSON input value ($), + then the .track accessor selected the JSON object + associated with the "track" object key, then + the .segments accessor selected the JSON array + associated with the "segments" key within that + object, then the [*] accessor selected each element + of that array (producing a series of items), then + the .location accessor selected the JSON array + associated with the "location" key within each of + those objects. In this example, each of those objects had + a "location" key; but if any of them did not, + the .location accessor would have simply produced no + output for that input item. + + + + To return the coordinates of the first segment only, you can + specify the corresponding subscript in the [] + accessor operator. Recall that JSON array indexes are 0-relative: + +=> select jsonb_path_query(:'json', '$.track.segments[0].location'); + jsonb_path_query +------------------- + [47.763, 13.4034] + + + + + The result of each path evaluation step can be processed + by one or more of the jsonpath operators and methods + listed in . + Each method name must be preceded by a dot. For example, + you can get the size of an array: + +=> select jsonb_path_query(:'json', '$.track.segments.size()'); + jsonb_path_query +------------------ + 2 + + More examples of using jsonpath operators + and methods within path expressions appear below in + . + + + + A path can also contain + filter expressions that work similarly to the + WHERE clause in SQL. A filter expression begins with + a question mark and provides a condition in parentheses: + + +? (condition) + + + + + Filter expressions must be written just after the path evaluation step + to which they should apply. The result of that step is filtered to include + only those items that satisfy the provided condition. SQL/JSON defines + three-valued logic, so the condition can + produce true, false, + or unknown. The unknown value + plays the same role as SQL NULL and can be tested + for with the is unknown predicate. Further path + evaluation steps use only those items for which the filter expression + returned true. + + + + The functions and operators that can be used in filter expressions are + listed in . Within a + filter expression, the @ variable denotes the value + being considered (i.e., one result of the preceding path step). You can + write accessor operators after @ to retrieve component + items. + + + + For example, suppose you would like to retrieve all heart rate values higher + than 130. You can achieve this as follows: + +=> select jsonb_path_query(:'json', '$.track.segments[*].HR ? (@ > 130)'); + jsonb_path_query +------------------ + 135 + + + + + To get the start times of segments with such values, you have to + filter out irrelevant segments before selecting the start times, so the + filter expression is applied to the previous step, and the path used + in the condition is different: + +=> select jsonb_path_query(:'json', '$.track.segments[*] ? (@.HR > 130)."start time"'); + jsonb_path_query +----------------------- + "2018-10-14 10:39:21" + + + + + You can use several filter expressions in sequence, if required. + The following example selects start times of all segments that + contain locations with relevant coordinates and high heart rate values: + +=> select jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] < 13.4) ? (@.HR > 130)."start time"'); + jsonb_path_query +----------------------- + "2018-10-14 10:39:21" + + + + + Using filter expressions at different nesting levels is also allowed. + The following example first filters all segments by location, and then + returns high heart rate values for these segments, if available: + +=> select jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] < 13.4).HR ? (@ > 130)'); + jsonb_path_query +------------------ + 135 + + + + + You can also nest filter expressions within each other. + This example returns the size of the track if it contains any + segments with high heart rate values, or an empty sequence otherwise: + +=> select jsonb_path_query(:'json', '$.track ? (exists(@.segments[*] ? (@.HR > 130))).segments.size()'); + jsonb_path_query +------------------ + 2 + + + + + Deviations from the SQL Standard + + PostgreSQL's implementation of the SQL/JSON path + language has the following deviations from the SQL/JSON standard. + + + + Boolean Predicate Check Expressions + + As an extension to the SQL standard, + a PostgreSQL path expression can be a + Boolean predicate, whereas the SQL standard allows predicates only within + filters. While SQL-standard path expressions return the relevant + element(s) of the queried JSON value, predicate check expressions + return the single three-valued jsonb result of the + predicate: true, + false, or null. + For example, we could write this SQL-standard filter expression: + +=> select jsonb_path_query(:'json', '$.track.segments ?(@[*].HR > 130)'); + jsonb_path_query +-----------------------------------------------------------&zwsp;---------------------- + {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"} + + The similar predicate check expression simply + returns true, indicating that a match exists: + +=> select jsonb_path_query(:'json', '$.track.segments[*].HR > 130'); + jsonb_path_query +------------------ + true + + + + + + Predicate check expressions are required in the + @@ operator (and the + jsonb_path_match function), and should not be used + with the @? operator (or the + jsonb_path_exists function). + + + + + + Regular Expression Interpretation + + There are minor differences in the interpretation of regular + expression patterns used in like_regex filters, as + described in . + + + + + + Strict and Lax Modes + + When you query JSON data, the path expression may not match the + actual JSON data structure. An attempt to access a non-existent + member of an object or element of an array is defined as a + structural error. SQL/JSON path expressions have two modes + of handling structural errors: + + + + + + lax (default) — the path engine implicitly adapts + the queried data to the specified path. + Any structural errors that cannot be fixed as described below + are suppressed, producing no match. + + + + + strict — if a structural error occurs, an error is raised. + + + + + + Lax mode facilitates matching of a JSON document and path + expression when the JSON data does not conform to the expected schema. + If an operand does not match the requirements of a particular operation, + it can be automatically wrapped as an SQL/JSON array, or unwrapped by + converting its elements into an SQL/JSON sequence before performing + the operation. Also, comparison operators automatically unwrap their + operands in lax mode, so you can compare SQL/JSON arrays + out-of-the-box. An array of size 1 is considered equal to its sole element. + Automatic unwrapping is not performed when: + + + + The path expression contains type() or + size() methods that return the type + and the number of elements in the array, respectively. + + + + + The queried JSON data contain nested arrays. In this case, only + the outermost array is unwrapped, while all the inner arrays + remain unchanged. Thus, implicit unwrapping can only go one + level down within each path evaluation step. + + + + + + + For example, when querying the GPS data listed above, you can + abstract from the fact that it stores an array of segments + when using lax mode: + +=> select jsonb_path_query(:'json', 'lax $.track.segments.location'); + jsonb_path_query +------------------- + [47.763, 13.4034] + [47.706, 13.2635] + + + + + In strict mode, the specified path must exactly match the structure of + the queried JSON document, so using this path + expression will cause an error: + +=> select jsonb_path_query(:'json', 'strict $.track.segments.location'); +ERROR: jsonpath member accessor can only be applied to an object + + To get the same result as in lax mode, you have to explicitly unwrap the + segments array: + +=> select jsonb_path_query(:'json', 'strict $.track.segments[*].location'); + jsonb_path_query +------------------- + [47.763, 13.4034] + [47.706, 13.2635] + + + + + The unwrapping behavior of lax mode can lead to surprising results. For + instance, the following query using the .** accessor + selects every HR value twice: + +=> select jsonb_path_query(:'json', 'lax $.**.HR'); + jsonb_path_query +------------------ + 73 + 135 + 73 + 135 + + This happens because the .** accessor selects both + the segments array and each of its elements, while + the .HR accessor automatically unwraps arrays when + using lax mode. To avoid surprising results, we recommend using + the .** accessor only in strict mode. The + following query selects each HR value just once: + +=> select jsonb_path_query(:'json', 'strict $.**.HR'); + jsonb_path_query +------------------ + 73 + 135 + + + + + The unwrapping of arrays can also lead to unexpected results. Consider this + example, which selects all the location arrays: + +=> select jsonb_path_query(:'json', 'lax $.track.segments[*].location'); + jsonb_path_query +------------------- + [47.763, 13.4034] + [47.706, 13.2635] +(2 rows) + + As expected it returns the full arrays. But applying a filter expression + causes the arrays to be unwrapped to evaluate each item, returning only the + items that match the expression: + +=> select jsonb_path_query(:'json', 'lax $.track.segments[*].location ?(@[*] > 15)'); + jsonb_path_query +------------------ + 47.763 + 47.706 +(2 rows) + + This despite the fact that the full arrays are selected by the path + expression. Use strict mode to restore selecting the arrays: + +=> select jsonb_path_query(:'json', 'strict $.track.segments[*].location ?(@[*] > 15)'); + jsonb_path_query +------------------- + [47.763, 13.4034] + [47.706, 13.2635] +(2 rows) + + + + + + SQL/JSON Path Operators and Methods + + + shows the operators and + methods available in jsonpath. Note that while the unary + operators and methods can be applied to multiple values resulting from a + preceding path step, the binary operators (addition etc.) can only be + applied to single values. In lax mode, methods applied to an array will be + executed for each value in the array. The exceptions are + .type() and .size(), which apply to + the array itself. + + + + <type>jsonpath</type> Operators and Methods + + + + + Operator/Method + + + Description + + + Example(s) + + + + + + + + number + number + number + + + Addition + + + jsonb_path_query('[2]', '$[0] + 3') + 5 + + + + + + + number + number + + + Unary plus (no operation); unlike addition, this can iterate over + multiple values + + + jsonb_path_query_array('{"x": [2,3,4]}', '+ $.x') + [2, 3, 4] + + + + + + number - number + number + + + Subtraction + + + jsonb_path_query('[2]', '7 - $[0]') + 5 + + + + + + - number + number + + + Negation; unlike subtraction, this can iterate over + multiple values + + + jsonb_path_query_array('{"x": [2,3,4]}', '- $.x') + [-2, -3, -4] + + + + + + number * number + number + + + Multiplication + + + jsonb_path_query('[4]', '2 * $[0]') + 8 + + + + + + number / number + number + + + Division + + + jsonb_path_query('[8.5]', '$[0] / 2') + 4.2500000000000000 + + + + + + number % number + number + + + Modulo (remainder) + + + jsonb_path_query('[32]', '$[0] % 10') + 2 + + + + + + value . type() + string + + + Type of the JSON item (see json_typeof) + + + jsonb_path_query_array('[1, "2", {}]', '$[*].type()') + ["number", "string", "object"] + + + + + + value . size() + number + + + Size of the JSON item (number of array elements, or 1 if not an + array) + + + jsonb_path_query('{"m": [11, 15]}', '$.m.size()') + 2 + + + + + + value . boolean() + boolean + + + Boolean value converted from a JSON boolean, number, or string + + + jsonb_path_query_array('[1, "yes", false]', '$[*].boolean()') + [true, true, false] + + + + + + value . string() + string + + + String value converted from a JSON boolean, number, string, or + datetime + + + jsonb_path_query_array('[1.23, "xyz", false]', '$[*].string()') + ["1.23", "xyz", "false"] + + + jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp().string()') + "2023-08-15T12:34:56" + + + + + + value . double() + number + + + Approximate floating-point number converted from a JSON number or + string + + + jsonb_path_query('{"len": "1.9"}', '$.len.double() * 2') + 3.8 + + + + + + number . ceiling() + number + + + Nearest integer greater than or equal to the given number + + + jsonb_path_query('{"h": 1.3}', '$.h.ceiling()') + 2 + + + + + + number . floor() + number + + + Nearest integer less than or equal to the given number + + + jsonb_path_query('{"h": 1.7}', '$.h.floor()') + 1 + + + + + + number . abs() + number + + + Absolute value of the given number + + + jsonb_path_query('{"z": -0.3}', '$.z.abs()') + 0.3 + + + + + + value . bigint() + bigint + + + Big integer value converted from a JSON number or string + + + jsonb_path_query('{"len": "9876543219"}', '$.len.bigint()') + 9876543219 + + + + + + value . decimal( [ precision [ , scale ] ] ) + decimal + + + Rounded decimal value converted from a JSON number or string + (precision and scale must be + integer values) + + + jsonb_path_query('1234.5678', '$.decimal(6, 2)') + 1234.57 + + + + + + value . integer() + integer + + + Integer value converted from a JSON number or string + + + jsonb_path_query('{"len": "12345"}', '$.len.integer()') + 12345 + + + + + + value . number() + numeric + + + Numeric value converted from a JSON number or string + + + jsonb_path_query('{"len": "123.45"}', '$.len.number()') + 123.45 + + + + + + string . datetime() + datetime_type + (see note) + + + Date/time value converted from a string + + + jsonb_path_query('["2015-8-1", "2015-08-12"]', '$[*] ? (@.datetime() < "2015-08-2".datetime())') + "2015-8-1" + + + + + + string . datetime(template) + datetime_type + (see note) + + + Date/time value converted from a string using the + specified to_timestamp template + + + jsonb_path_query_array('["12:30", "18:40"]', '$[*].datetime("HH24:MI")') + ["12:30:00", "18:40:00"] + + + + + + string . date() + date + + + Date value converted from a string + + + jsonb_path_query('"2023-08-15"', '$.date()') + "2023-08-15" + + + + + + string . time() + time without time zone + + + Time without time zone value converted from a string + + + jsonb_path_query('"12:34:56"', '$.time()') + "12:34:56" + + + + + + string . time(precision) + time without time zone + + + Time without time zone value converted from a string, with fractional + seconds adjusted to the given precision + + + jsonb_path_query('"12:34:56.789"', '$.time(2)') + "12:34:56.79" + + + + + + string . time_tz() + time with time zone + + + Time with time zone value converted from a string + + + jsonb_path_query('"12:34:56 +05:30"', '$.time_tz()') + "12:34:56+05:30" + + + + + + string . time_tz(precision) + time with time zone + + + Time with time zone value converted from a string, with fractional + seconds adjusted to the given precision + + + jsonb_path_query('"12:34:56.789 +05:30"', '$.time_tz(2)') + "12:34:56.79+05:30" + + + + + + string . timestamp() + timestamp without time zone + + + Timestamp without time zone value converted from a string + + + jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp()') + "2023-08-15T12:34:56" + + + + + + string . timestamp(precision) + timestamp without time zone + + + Timestamp without time zone value converted from a string, with + fractional seconds adjusted to the given precision + + + jsonb_path_query('"2023-08-15 12:34:56.789"', '$.timestamp(2)') + "2023-08-15T12:34:56.79" + + + + + + string . timestamp_tz() + timestamp with time zone + + + Timestamp with time zone value converted from a string + + + jsonb_path_query('"2023-08-15 12:34:56 +05:30"', '$.timestamp_tz()') + "2023-08-15T12:34:56+05:30" + + + + + + string . timestamp_tz(precision) + timestamp with time zone + + + Timestamp with time zone value converted from a string, with fractional + seconds adjusted to the given precision + + + jsonb_path_query('"2023-08-15 12:34:56.789 +05:30"', '$.timestamp_tz(2)') + "2023-08-15T12:34:56.79+05:30" + + + + + + object . keyvalue() + array + + + The object's key-value pairs, represented as an array of objects + containing three fields: "key", + "value", and "id"; + "id" is a unique identifier of the object the + key-value pair belongs to + + + jsonb_path_query_array('{"x": "20", "y": 32}', '$.keyvalue()') + [{"id": 0, "key": "x", "value": "20"}, {"id": 0, "key": "y", "value": 32}] + + + + +

+ + + + The result type of the datetime() and + datetime(template) + methods can be date, timetz, time, + timestamptz, or timestamp. + Both methods determine their result type dynamically. + + + The datetime() method sequentially tries to + match its input string to the ISO formats + for date, timetz, time, + timestamptz, and timestamp. It stops on + the first matching format and emits the corresponding data type. + + + The datetime(template) + method determines the result type according to the fields used in the + provided template string. + + + The datetime() and + datetime(template) methods + use the same parsing rules as the to_timestamp SQL + function does (see ), with three + exceptions. First, these methods don't allow unmatched template + patterns. Second, only the following separators are allowed in the + template string: minus sign, period, solidus (slash), comma, apostrophe, + semicolon, colon and space. Third, separators in the template string + must exactly match the input string. + + + If different date/time types need to be compared, an implicit cast is + applied. A date value can be cast to timestamp + or timestamptz, timestamp can be cast to + timestamptz, and time to timetz. + However, all but the first of these conversions depend on the current + setting, and thus can only be performed + within timezone-aware jsonpath functions. Similarly, other + date/time-related methods that convert strings to date/time types + also do this casting, which may involve the current + setting. Therefore, these conversions can + also only be performed within timezone-aware jsonpath + functions. + + + + + shows the available + filter expression elements. + + + + <type>jsonpath</type> Filter Expression Elements + + + + + Predicate/Value + + + Description + + + Example(s) + + + + + + + + value == value + boolean + + + Equality comparison (this, and the other comparison operators, work on + all JSON scalar values) + + + jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == 1)') + [1, 1] + + + jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == "a")') + ["a"] + + + + + + value != value + boolean + + + value <> value + boolean + + + Non-equality comparison + + + jsonb_path_query_array('[1, 2, 1, 3]', '$[*] ? (@ != 1)') + [2, 3] + + + jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ <> "b")') + ["a", "c"] + + + + + + value < value + boolean + + + Less-than comparison + + + jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ < 2)') + [1] + + + + + + value <= value + boolean + + + Less-than-or-equal-to comparison + + + jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ <= "b")') + ["a", "b"] + + + + + + value > value + boolean + + + Greater-than comparison + + + jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ > 2)') + [3] + + + + + + value >= value + boolean + + + Greater-than-or-equal-to comparison + + + jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ >= 2)') + [2, 3] + + + + + + true + boolean + + + JSON constant true + + + jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == true)') + {"name": "Chris", "parent": true} + + + + + + false + boolean + + + JSON constant false + + + jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == false)') + {"name": "John", "parent": false} + + + + + + null + value + + + JSON constant null (note that, unlike in SQL, + comparison to null works normally) + + + jsonb_path_query('[{"name": "Mary", "job": null}, {"name": "Michael", "job": "driver"}]', '$[*] ? (@.job == null) .name') + "Mary" + + + + + + boolean && boolean + boolean + + + Boolean AND + + + jsonb_path_query('[1, 3, 7]', '$[*] ? (@ > 1 && @ < 5)') + 3 + + + + + + boolean || boolean + boolean + + + Boolean OR + + + jsonb_path_query('[1, 3, 7]', '$[*] ? (@ < 1 || @ > 5)') + 7 + + + + + + ! boolean + boolean + + + Boolean NOT + + + jsonb_path_query('[1, 3, 7]', '$[*] ? (!(@ < 5))') + 7 + + + + + + boolean is unknown + boolean + + + Tests whether a Boolean condition is unknown. + + + jsonb_path_query('[-1, 2, 7, "foo"]', '$[*] ? ((@ > 0) is unknown)') + "foo" + + + + + + string like_regex string flag string + boolean + + + Tests whether the first operand matches the regular expression + given by the second operand, optionally with modifications + described by a string of flag characters (see + ). + + + jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c")') + ["abc", "abdacb"] + + + jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c" flag "i")') + ["abc", "aBdC", "abdacb"] + + + + + + string starts with string + boolean + + + Tests whether the second operand is an initial substring of the first + operand. + + + jsonb_path_query('["John Smith", "Mary Stone", "Bob Johnson"]', '$[*] ? (@ starts with "John")') + "John Smith" + + + + + + exists ( path_expression ) + boolean + + + Tests whether a path expression matches at least one SQL/JSON item. + Returns unknown if the path expression would result + in an error; the second example uses this to avoid a no-such-key error + in strict mode. + + + jsonb_path_query('{"x": [1, 2], "y": [2, 4]}', 'strict $.* ? (exists (@ ? (@[*] > 2)))') + [2, 4] + + + jsonb_path_query_array('{"value": 41}', 'strict $ ? (exists (@.name)) .name') + [] + + + + +

+ + + + + SQL/JSON Regular Expressions + + + LIKE_REGEX + in SQL/JSON + + + + SQL/JSON path expressions allow matching text to a regular expression + with the like_regex filter. For example, the + following SQL/JSON path query would case-insensitively match all + strings in an array that start with an English vowel: + +$[*] ? (@ like_regex "^[aeiou]" flag "i") + + + + + The optional flag string may include one or more of + the characters + i for case-insensitive match, + m to allow ^ + and $ to match at newlines, + s to allow . to match a newline, + and q to quote the whole pattern (reducing the + behavior to a simple substring match). + + + + The SQL/JSON standard borrows its definition for regular expressions + from the LIKE_REGEX operator, which in turn uses the + XQuery standard. PostgreSQL does not currently support the + LIKE_REGEX operator. Therefore, + the like_regex filter is implemented using the + POSIX regular expression engine described in + . This leads to various minor + discrepancies from standard SQL/JSON behavior, which are cataloged in + . + Note, however, that the flag-letter incompatibilities described there + do not apply to SQL/JSON, as it translates the XQuery flag letters to + match what the POSIX engine expects. + + + + Keep in mind that the pattern argument of like_regex + is a JSON path string literal, written according to the rules given in + . This means in particular that any + backslashes you want to use in the regular expression must be doubled. + For example, to match string values of the root document that contain + only digits: + +$.* ? (@ like_regex "^\\d+$") + + + + + + + SQL/JSON Query Functions + + SQL/JSON functions JSON_EXISTS(), + JSON_QUERY(), and JSON_VALUE() + described in can be used + to query JSON documents. Each of these functions apply a + path_expression (an SQL/JSON path query) to a + context_item (the document). See + for more details on what + the path_expression can contain. The + path_expression can also reference variables, + whose values are specified with their respective names in the + PASSING clause that is supported by each function. + context_item can be a jsonb value + or a character string that can be successfully cast to jsonb. + + + + SQL/JSON Query Functions + + + + + Function signature + + + Description + + + Example(s) + + + + + + + json_exists + +JSON_EXISTS ( +context_item, path_expression + PASSING { value AS varname } , ... +{ TRUE | FALSE | UNKNOWN | ERROR } ON ERROR ) boolean + + + + + + Returns true if the SQL/JSON path_expression + applied to the context_item yields any + items, false otherwise. + + + + + The ON ERROR clause specifies the behavior if + an error occurs during path_expression + evaluation. Specifying ERROR will cause an error to + be thrown with the appropriate message. Other options include + returning boolean values FALSE or + TRUE or the value UNKNOWN which + is actually an SQL NULL. The default when no ON ERROR + clause is specified is to return the boolean value + FALSE. + + + + + Examples: + + + JSON_EXISTS(jsonb '{"key1": [1,2,3]}', 'strict $.key1[*] ? (@ > $x)' PASSING 2 AS x) + t + + + JSON_EXISTS(jsonb '{"a": [1,2,3]}', 'lax $.a[5]' ERROR ON ERROR) + f + + + JSON_EXISTS(jsonb '{"a": [1,2,3]}', 'strict $.a[5]' ERROR ON ERROR) + + +ERROR: jsonpath array subscript is out of bounds + + + + + + json_query + +JSON_QUERY ( +context_item, path_expression + PASSING { value AS varname } , ... + RETURNING data_type FORMAT JSON ENCODING UTF8 + { WITHOUT | WITH { CONDITIONAL | UNCONDITIONAL } } ARRAY WRAPPER + { KEEP | OMIT } QUOTES ON SCALAR STRING + { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON EMPTY + { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON ERROR ) jsonb + + + + + + Returns the result of applying the SQL/JSON + path_expression to the + context_item. + + + + + By default, the result is returned as a value of type jsonb, + though the RETURNING clause can be used to return + as some other type to which it can be successfully coerced. + + + + + If the path expression may return multiple values, it might be necessary + to wrap those values using the WITH WRAPPER clause to + make it a valid JSON string, because the default behavior is to not wrap + them, as if WITHOUT WRAPPER were specified. The + WITH WRAPPER clause is by default taken to mean + WITH UNCONDITIONAL WRAPPER, which means that even a + single result value will be wrapped. To apply the wrapper only when + multiple values are present, specify WITH CONDITIONAL WRAPPER. + Getting multiple values in result will be treated as an error if + WITHOUT WRAPPER is specified. + + + + + If the result is a scalar string, by default, the returned value will + be surrounded by quotes, making it a valid JSON value. It can be made + explicit by specifying KEEP QUOTES. Conversely, + quotes can be omitted by specifying OMIT QUOTES. + To ensure that the result is a valid JSON value, OMIT QUOTES + cannot be specified when WITH WRAPPER is also + specified. + + + + + The ON EMPTY clause specifies the behavior if + evaluating path_expression yields an empty + set. The ON ERROR clause specifies the behavior + if an error occurs when evaluating path_expression, + when coercing the result value to the RETURNING type, + or when evaluating the ON EMPTY expression if the + path_expression evaluation returns an empty + set. + + + + + For both ON EMPTY and ON ERROR, + specifying ERROR will cause an error to be thrown with + the appropriate message. Other options include returning an SQL NULL, an + empty array (EMPTY ARRAY), + an empty object (EMPTY OBJECT), or a user-specified + expression (DEFAULT expression) + that can be coerced to jsonb or the type specified in RETURNING. + The default when ON EMPTY or ON ERROR + is not specified is to return an SQL NULL value. + + + + + Examples: + + + JSON_QUERY(jsonb '[1,[2,3],null]', 'lax $[*][$off]' PASSING 1 AS off WITH CONDITIONAL WRAPPER) + 3 + + + JSON_QUERY(jsonb '{"a": "[1, 2]"}', 'lax $.a' OMIT QUOTES) + [1, 2] + + + JSON_QUERY(jsonb '{"a": "[1, 2]"}', 'lax $.a' RETURNING int[] OMIT QUOTES ERROR ON ERROR) + + +ERROR: malformed array literal: "[1, 2]" +DETAIL: Missing "]" after array dimensions. + + + + + + + json_value + +JSON_VALUE ( +context_item, path_expression + PASSING { value AS varname } , ... + RETURNING data_type + { ERROR | NULL | DEFAULT expression } ON EMPTY + { ERROR | NULL | DEFAULT expression } ON ERROR ) text + + + + + + Returns the result of applying the SQL/JSON + path_expression to the + context_item. + + + + + Only use JSON_VALUE() if the extracted value is + expected to be a single SQL/JSON scalar item; + getting multiple values will be treated as an error. If you expect that + extracted value might be an object or an array, use the + JSON_QUERY function instead. + + + + + By default, the result, which must be a single scalar value, is + returned as a value of type text, though the + RETURNING clause can be used to return as some + other type to which it can be successfully coerced. + + + + + The ON ERROR and ON EMPTY + clauses have similar semantics as mentioned in the description of + JSON_QUERY, except the set of values returned in + lieu of throwing an error is different. + + + + + Note that scalar strings returned by JSON_VALUE + always have their quotes removed, equivalent to specifying + OMIT QUOTES in JSON_QUERY. + + + + + Examples: + + + JSON_VALUE(jsonb '"123.45"', '$' RETURNING float) + 123.45 + + + JSON_VALUE(jsonb '"03:04 2015-02-01"', '$.datetime("HH24:MI YYYY-MM-DD")' RETURNING date) + 2015-02-01 + + + JSON_VALUE(jsonb '[1,2]', 'strict $[$off]' PASSING 1 as off) + 2 + + + JSON_VALUE(jsonb '[1,2]', 'strict $[*]' DEFAULT 9 ON ERROR) + 9 + + + + + +

+ + + The context_item expression is converted to + jsonb by an implicit cast if the expression is not already of + type jsonb. Note, however, that any parsing errors that occur + during that conversion are thrown unconditionally, that is, are not + handled according to the (specified or implicit) ON ERROR + clause. + + + + + JSON_VALUE() returns an SQL NULL if + path_expression returns a JSON + null, whereas JSON_QUERY() returns + the JSON null as is. + + + + + + JSON_TABLE + + json_table + + + + JSON_TABLE is an SQL/JSON function which + queries JSON data + and presents the results as a relational view, which can be accessed as a + regular SQL table. You can use JSON_TABLE inside + the FROM clause of a SELECT, + UPDATE, or DELETE and as data source + in a MERGE statement. + + + + Taking JSON data as input, JSON_TABLE uses a JSON path + expression to extract a part of the provided data to use as a + row pattern for the constructed view. Each SQL/JSON + value given by the row pattern serves as source for a separate row in the + constructed view. + + + + To split the row pattern into columns, JSON_TABLE + provides the COLUMNS clause that defines the + schema of the created view. For each column, a separate JSON path expression + can be specified to be evaluated against the row pattern to get an SQL/JSON + value that will become the value for the specified column in a given output + row. + + + + JSON data stored at a nested level of the row pattern can be extracted using + the NESTED PATH clause. Each + NESTED PATH clause can be used to generate one or more + columns using the data from a nested level of the row pattern. Those + columns can be specified using a COLUMNS clause that + looks similar to the top-level COLUMNS clause. Rows constructed from + NESTED COLUMNS are called child rows and are joined + against the row constructed from the columns specified in the parent + COLUMNS clause to get the row in the final view. Child + columns themselves may contain a NESTED PATH + specification thus allowing to extract data located at arbitrary nesting + levels. Columns produced by multiple NESTED PATHs at the + same level are considered to be siblings of each + other and their rows after joining with the parent row are combined using + UNION. + + + + The rows produced by JSON_TABLE are laterally + joined to the row that generated them, so you do not have to explicitly join + the constructed view with the original table holding JSON + data. + + + + The syntax is: + + + +JSON_TABLE ( + context_item, path_expression AS json_path_name PASSING { value AS varname } , ... + COLUMNS ( json_table_column , ... ) + { ERROR | EMPTY ARRAY} ON ERROR +) + + +where json_table_column is: + + name FOR ORDINALITY + | name type + FORMAT JSON ENCODING UTF8 + PATH path_expression + { WITHOUT | WITH { CONDITIONAL | UNCONDITIONAL } } ARRAY WRAPPER + { KEEP | OMIT } QUOTES ON SCALAR STRING + { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON EMPTY + { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON ERROR + | name type EXISTS PATH path_expression + { ERROR | TRUE | FALSE | UNKNOWN } ON ERROR + | NESTED PATH path_expression AS json_path_name COLUMNS ( json_table_column , ... ) + + + + Each syntax element is described below in more detail. + + + + + + context_item, path_expression AS json_path_name PASSING { value AS varname } , ... + + + + The context_item specifies the input document + to query, the path_expression is an SQL/JSON + path expression defining the query, and json_path_name + is an optional name for the path_expression. + The optional PASSING clause provides data values for + the variables mentioned in the path_expression. + The result of the input data evaluation using the aforementioned elements + is called the row pattern, which is used as the + source for row values in the constructed view. + + + + + + + COLUMNS ( json_table_column , ... ) + + + + + The COLUMNS clause defining the schema of the + constructed view. In this clause, you can specify each column to be + filled with an SQL/JSON value obtained by applying a JSON path expression + against the row pattern. json_table_column has + the following variants: + + + + + + name FOR ORDINALITY + + + + Adds an ordinality column that provides sequential row numbering starting + from 1. Each NESTED PATH (see below) gets its own + counter for any nested ordinality columns. + + + + + + + name type + FORMAT JSON ENCODING UTF8 + PATH path_expression + + + + Inserts an SQL/JSON value obtained by applying + path_expression against the row pattern into + the view's output row after coercing it to specified + type. + + + Specifying FORMAT JSON makes it explicit that you + expect the value to be a valid json object. It only + makes sense to specify FORMAT JSON if + type is one of bpchar, + bytea, character varying, name, + json, jsonb, text, or a domain over + these types. + + + Optionally, you can specify WRAPPER and + QUOTES clauses to format the output. Note that + specifying OMIT QUOTES overrides + FORMAT JSON if also specified, because unquoted + literals do not constitute valid json values. + + + Optionally, you can use ON EMPTY and + ON ERROR clauses to specify whether to throw the error + or return the specified value when the result of JSON path evaluation is + empty and when an error occurs during JSON path evaluation or when + coercing the SQL/JSON value to the specified type, respectively. The + default for both is to return a NULL value. + + + + This clause is internally turned into and has the same semantics as + JSON_VALUE or JSON_QUERY. + The latter if the specified type is not a scalar type or if either of + FORMAT JSON, WRAPPER, or + QUOTES clause is present. + + + + + + + + name type + EXISTS PATH path_expression + + + + Inserts a boolean value obtained by applying + path_expression against the row pattern + into the view's output row after coercing it to specified + type. + + + The value corresponds to whether applying the PATH + expression to the row pattern yields any values. + + + The specified type should have a cast from the + boolean type. + + + Optionally, you can use ON ERROR to specify whether to + throw the error or return the specified value when an error occurs during + JSON path evaluation or when coercing SQL/JSON value to the specified + type. The default is to return a boolean value + FALSE. + + + + This clause is internally turned into and has the same semantics as + JSON_EXISTS. + + + + + + + + NESTED PATH path_expression AS json_path_name + COLUMNS ( json_table_column , ... ) + + + + + Extracts SQL/JSON values from nested levels of the row pattern, + generates one or more columns as defined by the COLUMNS + subclause, and inserts the extracted SQL/JSON values into those + columns. The json_table_column + expression in the COLUMNS subclause uses the same + syntax as in the parent COLUMNS clause. + + + + The NESTED PATH syntax is recursive, + so you can go down multiple nested levels by specifying several + NESTED PATH subclauses within each other. + It allows to unnest the hierarchy of JSON objects and arrays + in a single function invocation rather than chaining several + JSON_TABLE expressions in an SQL statement. + + + + + + + + In each variant of json_table_column described + above, if the PATH clause is omitted, path expression + $.name is used, where + name is the provided column name. + + + + + + + + + AS json_path_name + + + + + The optional json_path_name serves as an + identifier of the provided path_expression. + The name must be unique and distinct from the column names. + + + + + + + { ERROR | EMPTY } ON ERROR + + + + + The optional ON ERROR can be used to specify how to + handle errors when evaluating the top-level + path_expression. Use ERROR + if you want the errors to be thrown and EMPTY to + return an empty table, that is, a table containing 0 rows. Note that + this clause does not affect the errors that occur when evaluating + columns, for which the behavior depends on whether the + ON ERROR clause is specified against a given column. + + + + + + Examples + + + In the examples that follow, the following table containing JSON data + will be used: + + +CREATE TABLE my_films ( js jsonb ); + +INSERT INTO my_films VALUES ( +'{ "favorites" : [ + { "kind" : "comedy", "films" : [ + { "title" : "Bananas", + "director" : "Woody Allen"}, + { "title" : "The Dinner Game", + "director" : "Francis Veber" } ] }, + { "kind" : "horror", "films" : [ + { "title" : "Psycho", + "director" : "Alfred Hitchcock" } ] }, + { "kind" : "thriller", "films" : [ + { "title" : "Vertigo", + "director" : "Alfred Hitchcock" } ] }, + { "kind" : "drama", "films" : [ + { "title" : "Yojimbo", + "director" : "Akira Kurosawa" } ] } + ] }'); + + + + + The following query shows how to use JSON_TABLE to + turn the JSON objects in the my_films table + to a view containing columns for the keys kind, + title, and director contained in + the original JSON along with an ordinality column: + + +SELECT jt.* FROM + my_films, + JSON_TABLE (js, '$.favorites[*]' COLUMNS ( + id FOR ORDINALITY, + kind text PATH '$.kind', + title text PATH '$.films[*].title' WITH WRAPPER, + director text PATH '$.films[*].director' WITH WRAPPER)) AS jt; + + + + id | kind | title | director +----+----------+--------------------------------+---------------------------------- + 1 | comedy | ["Bananas", "The Dinner Game"] | ["Woody Allen", "Francis Veber"] + 2 | horror | ["Psycho"] | ["Alfred Hitchcock"] + 3 | thriller | ["Vertigo"] | ["Alfred Hitchcock"] + 4 | drama | ["Yojimbo"] | ["Akira Kurosawa"] +(4 rows) + + + + + The following is a modified version of the above query to show the + usage of PASSING arguments in the filter specified in + the top-level JSON path expression and the various options for the + individual columns: + + +SELECT jt.* FROM + my_films, + JSON_TABLE (js, '$.favorites[*] ? (@.films[*].director == $filter)' + PASSING 'Alfred Hitchcock' AS filter + COLUMNS ( + id FOR ORDINALITY, + kind text PATH '$.kind', + title text FORMAT JSON PATH '$.films[*].title' OMIT QUOTES, + director text PATH '$.films[*].director' KEEP QUOTES)) AS jt; + + + + id | kind | title | director +----+----------+---------+-------------------- + 1 | horror | Psycho | "Alfred Hitchcock" + 2 | thriller | Vertigo | "Alfred Hitchcock" +(2 rows) + + + + + The following is a modified version of the above query to show the usage + of NESTED PATH for populating title and director + columns, illustrating how they are joined to the parent columns id and + kind: + + +SELECT jt.* FROM + my_films, + JSON_TABLE ( js, '$.favorites[*] ? (@.films[*].director == $filter)' + PASSING 'Alfred Hitchcock' AS filter + COLUMNS ( + id FOR ORDINALITY, + kind text PATH '$.kind', + NESTED PATH '$.films[*]' COLUMNS ( + title text FORMAT JSON PATH '$.title' OMIT QUOTES, + director text PATH '$.director' KEEP QUOTES))) AS jt; + + + + id | kind | title | director +----+----------+---------+-------------------- + 1 | horror | Psycho | "Alfred Hitchcock" + 2 | thriller | Vertigo | "Alfred Hitchcock" +(2 rows) + + + + + + The following is the same query but without the filter in the root + path: + + +SELECT jt.* FROM + my_films, + JSON_TABLE ( js, '$.favorites[*]' + COLUMNS ( + id FOR ORDINALITY, + kind text PATH '$.kind', + NESTED PATH '$.films[*]' COLUMNS ( + title text FORMAT JSON PATH '$.title' OMIT QUOTES, + director text PATH '$.director' KEEP QUOTES))) AS jt; + + + + id | kind | title | director +----+----------+-----------------+-------------------- + 1 | comedy | Bananas | "Woody Allen" + 1 | comedy | The Dinner Game | "Francis Veber" + 2 | horror | Psycho | "Alfred Hitchcock" + 3 | thriller | Vertigo | "Alfred Hitchcock" + 4 | drama | Yojimbo | "Akira Kurosawa" +(5 rows) + + + + + + The following shows another query using a different JSON + object as input. It shows the UNION "sibling join" between + NESTED paths $.movies[*] and + $.books[*] and also the usage of + FOR ORDINALITY column at NESTED + levels (columns movie_id, book_id, + and author_id): + + +SELECT * FROM JSON_TABLE ( +'{"favorites": + [{"movies": + [{"name": "One", "director": "John Doe"}, + {"name": "Two", "director": "Don Joe"}], + "books": + [{"name": "Mystery", "authors": [{"name": "Brown Dan"}]}, + {"name": "Wonder", "authors": [{"name": "Jun Murakami"}, {"name":"Craig Doe"}]}] +}]}'::json, '$.favorites[*]' +COLUMNS ( + user_id FOR ORDINALITY, + NESTED '$.movies[*]' + COLUMNS ( + movie_id FOR ORDINALITY, + mname text PATH '$.name', + director text), + NESTED '$.books[*]' + COLUMNS ( + book_id FOR ORDINALITY, + bname text PATH '$.name', + NESTED '$.authors[*]' + COLUMNS ( + author_id FOR ORDINALITY, + author_name text PATH '$.name')))); + + + + user_id | movie_id | mname | director | book_id | bname | author_id | author_name +---------+----------+-------+----------+---------+---------+-----------+-------------- + 1 | 1 | One | John Doe | | | | + 1 | 2 | Two | Don Joe | | | | + 1 | | | | 1 | Mystery | 1 | Brown Dan + 1 | | | | 2 | Wonder | 1 | Jun Murakami + 1 | | | | 2 | Wonder | 2 | Craig Doe +(5 rows) + + + + + diff --git a/doc/src/sgml/func/func-logical.sgml b/doc/src/sgml/func/func-logical.sgml new file mode 100644 index 00000000000..65e50e65a81 --- /dev/null +++ b/doc/src/sgml/func/func-logical.sgml @@ -0,0 +1,146 @@ + + Logical Operators + + + operator + logical + + + + Boolean + operators + operators, logical + + + + The usual logical operators are available: + + + AND (operator) + + + + OR (operator) + + + + NOT (operator) + + + + conjunction + + + + disjunction + + + + negation + + + +boolean AND boolean boolean +boolean OR boolean boolean +NOT boolean boolean + + + SQL uses a three-valued logic system with true, + false, and null, which represents unknown. + Observe the following truth tables: + + + + + + a + b + a AND b + a OR b + + + + + + TRUE + TRUE + TRUE + TRUE + + + + TRUE + FALSE + FALSE + TRUE + + + + TRUE + NULL + NULL + TRUE + + + + FALSE + FALSE + FALSE + FALSE + + + + FALSE + NULL + FALSE + NULL + + + + NULL + NULL + NULL + NULL + + + + + + + + + + a + NOT a + + + + + + TRUE + FALSE + + + + FALSE + TRUE + + + + NULL + NULL + + + + + + + + The operators AND and OR are + commutative, that is, you can switch the left and right operands + without affecting the result. (However, it is not guaranteed that + the left operand is evaluated before the right operand. See for more information about the + order of evaluation of subexpressions.) + + diff --git a/doc/src/sgml/func/func-matching.sgml b/doc/src/sgml/func/func-matching.sgml new file mode 100644 index 00000000000..7d44e2a27bc --- /dev/null +++ b/doc/src/sgml/func/func-matching.sgml @@ -0,0 +1,2471 @@ + + Pattern Matching + + + pattern matching + + + + There are three separate approaches to pattern matching provided + by PostgreSQL: the traditional + SQL LIKE operator, the + more recent SIMILAR TO operator (added in + SQL:1999), and POSIX-style regular + expressions. Aside from the basic does this string match + this pattern? operators, functions are available to extract + or replace matching substrings and to split a string at matching + locations. + + + + + If you have pattern matching needs that go beyond this, + consider writing a user-defined function in Perl or Tcl. + + + + + + While most regular-expression searches can be executed very quickly, + regular expressions can be contrived that take arbitrary amounts of + time and memory to process. Be wary of accepting regular-expression + search patterns from hostile sources. If you must do so, it is + advisable to impose a statement timeout. + + + + Searches using SIMILAR TO patterns have the same + security hazards, since SIMILAR TO provides many + of the same capabilities as POSIX-style regular + expressions. + + + + LIKE searches, being much simpler than the other + two options, are safer to use with possibly-hostile pattern sources. + + + + + SIMILAR TO and POSIX-style regular + expressions do not support nondeterministic collations. If required, use + LIKE or apply a different collation to the expression + to work around this limitation. + + + + <function>LIKE</function> + + + LIKE + + + +string LIKE pattern ESCAPE escape-character +string NOT LIKE pattern ESCAPE escape-character + + + + The LIKE expression returns true if the + string matches the supplied + pattern. (As + expected, the NOT LIKE expression returns + false if LIKE returns true, and vice versa. + An equivalent expression is + NOT (string LIKE + pattern).) + + + + If pattern does not contain percent + signs or underscores, then the pattern only represents the string + itself; in that case LIKE acts like the + equals operator. An underscore (_) in + pattern stands for (matches) any single + character; a percent sign (%) matches any sequence + of zero or more characters. + + + + Some examples: + +'abc' LIKE 'abc' true +'abc' LIKE 'a%' true +'abc' LIKE '_b_' true +'abc' LIKE 'c' false + + + + + LIKE pattern matching supports nondeterministic + collations (see ), such as + case-insensitive collations or collations that, say, ignore punctuation. + So with a case-insensitive collation, one could have: + +'AbC' LIKE 'abc' COLLATE case_insensitive true +'AbC' LIKE 'a%' COLLATE case_insensitive true + + With collations that ignore certain characters or in general that consider + strings of different lengths equal, the semantics can become a bit more + complicated. Consider these examples: + +'.foo.' LIKE 'foo' COLLATE ign_punct true +'.foo.' LIKE 'f_o' COLLATE ign_punct true +'.foo.' LIKE '_oo' COLLATE ign_punct false + + The way the matching works is that the pattern is partitioned into + sequences of wildcards and non-wildcard strings (wildcards being + _ and %). For example, the pattern + f_o is partitioned into f, _, o, the + pattern _oo is partitioned into _, + oo. The input string matches the pattern if it can be + partitioned in such a way that the wildcards match one character or any + number of characters respectively and the non-wildcard partitions are + equal under the applicable collation. So for example, '.foo.' + LIKE 'f_o' COLLATE ign_punct is true because one can partition + .foo. into .f, o, o., and then + '.f' = 'f' COLLATE ign_punct, 'o' + matches the _ wildcard, and 'o.' = 'o' COLLATE + ign_punct. But '.foo.' LIKE '_oo' COLLATE + ign_punct is false because .foo. cannot be + partitioned in a way that the first character is any character and the + rest of the string compares equal to oo. (Note that + the single-character wildcard always matches exactly one character, + independent of the collation. So in this example, the + _ would match ., but then the rest + of the input string won't match the rest of the pattern.) + + + + LIKE pattern matching always covers the entire + string. Therefore, if it's desired to match a sequence anywhere within + a string, the pattern must start and end with a percent sign. + + + + To match a literal underscore or percent sign without matching + other characters, the respective character in + pattern must be + preceded by the escape character. The default escape + character is the backslash but a different one can be selected by + using the ESCAPE clause. To match the escape + character itself, write two escape characters. + + + + + If you have turned off, + any backslashes you write in literal string constants will need to be + doubled. See for more information. + + + + + It's also possible to select no escape character by writing + ESCAPE ''. This effectively disables the + escape mechanism, which makes it impossible to turn off the + special meaning of underscore and percent signs in the pattern. + + + + According to the SQL standard, omitting ESCAPE + means there is no escape character (rather than defaulting to a + backslash), and a zero-length ESCAPE value is + disallowed. PostgreSQL's behavior in + this regard is therefore slightly nonstandard. + + + + The key word ILIKE can be used instead of + LIKE to make the match case-insensitive according to the + active locale. (But this does not support nondeterministic collations.) + This is not in the SQL standard but is a + PostgreSQL extension. + + + + The operator ~~ is equivalent to + LIKE, and ~~* corresponds to + ILIKE. There are also + !~~ and !~~* operators that + represent NOT LIKE and NOT + ILIKE, respectively. All of these operators are + PostgreSQL-specific. You may see these + operator names in EXPLAIN output and similar + places, since the parser actually translates LIKE + et al. to these operators. + + + + The phrases LIKE, ILIKE, + NOT LIKE, and NOT ILIKE are + generally treated as operators + in PostgreSQL syntax; for example they can + be used in expression + operator ANY + (subquery) constructs, although + an ESCAPE clause cannot be included there. In some + obscure cases it may be necessary to use the underlying operator names + instead. + + + + Also see the starts-with operator ^@ and the + corresponding starts_with() function, which are + useful in cases where simply matching the beginning of a string is + needed. + + + + + + <function>SIMILAR TO</function> Regular Expressions + + + regular expression + + + + + SIMILAR TO + + + substring + + + +string SIMILAR TO pattern ESCAPE escape-character +string NOT SIMILAR TO pattern ESCAPE escape-character + + + + The SIMILAR TO operator returns true or + false depending on whether its pattern matches the given string. + It is similar to LIKE, except that it + interprets the pattern using the SQL standard's definition of a + regular expression. SQL regular expressions are a curious cross + between LIKE notation and common (POSIX) regular + expression notation. + + + + Like LIKE, the SIMILAR TO + operator succeeds only if its pattern matches the entire string; + this is unlike common regular expression behavior where the pattern + can match any part of the string. + Also like + LIKE, SIMILAR TO uses + _ and % as wildcard characters denoting + any single character and any string, respectively (these are + comparable to . and .* in POSIX regular + expressions). + + + + In addition to these facilities borrowed from LIKE, + SIMILAR TO supports these pattern-matching + metacharacters borrowed from POSIX regular expressions: + + + + + | denotes alternation (either of two alternatives). + + + + + * denotes repetition of the previous item zero + or more times. + + + + + + denotes repetition of the previous item one + or more times. + + + + + ? denotes repetition of the previous item zero + or one time. + + + + + {m} denotes repetition + of the previous item exactly m times. + + + + + {m,} denotes repetition + of the previous item m or more times. + + + + + {m,n} + denotes repetition of the previous item at least m and + not more than n times. + + + + + Parentheses () can be used to group items into + a single logical item. + + + + + A bracket expression [...] specifies a character + class, just as in POSIX regular expressions. + + + + + Notice that the period (.) is not a metacharacter + for SIMILAR TO. + + + + As with LIKE, a backslash disables the special + meaning of any of these metacharacters. A different escape character + can be specified with ESCAPE, or the escape + capability can be disabled by writing ESCAPE ''. + + + + According to the SQL standard, omitting ESCAPE + means there is no escape character (rather than defaulting to a + backslash), and a zero-length ESCAPE value is + disallowed. PostgreSQL's behavior in + this regard is therefore slightly nonstandard. + + + + Another nonstandard extension is that following the escape character + with a letter or digit provides access to the escape sequences + defined for POSIX regular expressions; see + , + , and + below. + + + + Some examples: + +'abc' SIMILAR TO 'abc' true +'abc' SIMILAR TO 'a' false +'abc' SIMILAR TO '%(b|d)%' true +'abc' SIMILAR TO '(b|c)%' false +'-abc-' SIMILAR TO '%\mabc\M%' true +'xabcy' SIMILAR TO '%\mabc\M%' false + + + + + The substring function with three parameters + provides extraction of a substring that matches an SQL + regular expression pattern. The function can be written according + to standard SQL syntax: + +substring(string similar pattern escape escape-character) + + or using the now obsolete SQL:1999 syntax: + +substring(string from pattern for escape-character) + + or as a plain three-argument function: + +substring(string, pattern, escape-character) + + As with SIMILAR TO, the + specified pattern must match the entire data string, or else the + function fails and returns null. To indicate the part of the + pattern for which the matching data sub-string is of interest, + the pattern should contain + two occurrences of the escape character followed by a double quote + ("). + The text matching the portion of the pattern + between these separators is returned when the match is successful. + + + + The escape-double-quote separators actually + divide substring's pattern into three independent + regular expressions; for example, a vertical bar (|) + in any of the three sections affects only that section. Also, the first + and third of these regular expressions are defined to match the smallest + possible amount of text, not the largest, when there is any ambiguity + about how much of the data string matches which pattern. (In POSIX + parlance, the first and third regular expressions are forced to be + non-greedy.) + + + + As an extension to the SQL standard, PostgreSQL + allows there to be just one escape-double-quote separator, in which case + the third regular expression is taken as empty; or no separators, in which + case the first and third regular expressions are taken as empty. + + + + Some examples, with #" delimiting the return string: + +substring('foobar' similar '%#"o_b#"%' escape '#') oob +substring('foobar' similar '#"o_b#"%' escape '#') NULL + + + + + + <acronym>POSIX</acronym> Regular Expressions + + + regular expression + pattern matching + + + substring + + + regexp_count + + + regexp_instr + + + regexp_like + + + regexp_match + + + regexp_matches + + + regexp_replace + + + regexp_split_to_table + + + regexp_split_to_array + + + regexp_substr + + + + lists the available + operators for pattern matching using POSIX regular expressions. + + + + Regular Expression Match Operators + + + + + + Operator + + + Description + + + Example(s) + + + + + + + + text ~ text + boolean + + + String matches regular expression, case sensitively + + + 'thomas' ~ 't.*ma' + t + + + + + + text ~* text + boolean + + + String matches regular expression, case-insensitively + + + 'thomas' ~* 'T.*ma' + t + + + + + + text !~ text + boolean + + + String does not match regular expression, case sensitively + + + 'thomas' !~ 't.*max' + t + + + + + + text !~* text + boolean + + + String does not match regular expression, case-insensitively + + + 'thomas' !~* 'T.*ma' + f + + + + +

+ + + POSIX regular expressions provide a more + powerful means for pattern matching than the LIKE and + SIMILAR TO operators. + Many Unix tools such as egrep, + sed, or awk use a pattern + matching language that is similar to the one described here. + + + + A regular expression is a character sequence that is an + abbreviated definition of a set of strings (a regular + set). A string is said to match a regular expression + if it is a member of the regular set described by the regular + expression. As with LIKE, pattern characters + match string characters exactly unless they are special characters + in the regular expression language — but regular expressions use + different special characters than LIKE does. + Unlike LIKE patterns, a + regular expression is allowed to match anywhere within a string, unless + the regular expression is explicitly anchored to the beginning or + end of the string. + + + + Some examples: + +'abcd' ~ 'bc' true +'abcd' ~ 'a.c' true — dot matches any character +'abcd' ~ 'a.*d' true — * repeats the preceding pattern item +'abcd' ~ '(b|x)' true — | means OR, parentheses group +'abcd' ~ '^a' true — ^ anchors to start of string +'abcd' ~ '^(b|c)' false — would match except for anchoring + + + + + The POSIX pattern language is described in much + greater detail below. + + + + The substring function with two parameters, + substring(string from + pattern), provides extraction of a + substring + that matches a POSIX regular expression pattern. It returns null if + there is no match, otherwise the first portion of the text that matched the + pattern. But if the pattern contains any parentheses, the portion + of the text that matched the first parenthesized subexpression (the + one whose left parenthesis comes first) is + returned. You can put parentheses around the whole expression + if you want to use parentheses within it without triggering this + exception. If you need parentheses in the pattern before the + subexpression you want to extract, see the non-capturing parentheses + described below. + + + + Some examples: + +substring('foobar' from 'o.b') oob +substring('foobar' from 'o(.)b') o + + + + + The regexp_count function counts the number of + places where a POSIX regular expression pattern matches a string. + It has the syntax + regexp_count(string, + pattern + , start + , flags + ). + pattern is searched for + in string, normally from the beginning of + the string, but if the start parameter is + provided then beginning from that character index. + The flags parameter is an optional text + string containing zero or more single-letter flags that change the + function's behavior. For example, including i in + flags specifies case-insensitive matching. + Supported flags are described in + . + + + + Some examples: + +regexp_count('ABCABCAXYaxy', 'A.') 3 +regexp_count('ABCABCAXYaxy', 'A.', 1, 'i') 4 + + + + + The regexp_instr function returns the starting or + ending position of the N'th match of a + POSIX regular expression pattern to a string, or zero if there is no + such match. It has the syntax + regexp_instr(string, + pattern + , start + , N + , endoption + , flags + , subexpr + ). + pattern is searched for + in string, normally from the beginning of + the string, but if the start parameter is + provided then beginning from that character index. + If N is specified + then the N'th match of the pattern + is located, otherwise the first match is located. + If the endoption parameter is omitted or + specified as zero, the function returns the position of the first + character of the match. Otherwise, endoption + must be one, and the function returns the position of the character + following the match. + The flags parameter is an optional text + string containing zero or more single-letter flags that change the + function's behavior. Supported flags are described + in . + For a pattern containing parenthesized + subexpressions, subexpr is an integer + indicating which subexpression is of interest: the result identifies + the position of the substring matching that subexpression. + Subexpressions are numbered in the order of their leading parentheses. + When subexpr is omitted or zero, the result + identifies the position of the whole match regardless of + parenthesized subexpressions. + + + + Some examples: + +regexp_instr('number of your street, town zip, FR', '[^,]+', 1, 2) + 23 +regexp_instr(string=>'ABCDEFGHI', pattern=>'(c..)(...)', start=>1, "N"=>1, endoption=>0, flags=>'i', subexpr=>2) + 6 + + + + + The regexp_like function checks whether a match + of a POSIX regular expression pattern occurs within a string, + returning boolean true or false. It has the syntax + regexp_like(string, + pattern + , flags ). + The flags parameter is an optional text + string containing zero or more single-letter flags that change the + function's behavior. Supported flags are described + in . + This function has the same results as the ~ + operator if no flags are specified. If only the i + flag is specified, it has the same results as + the ~* operator. + + + + Some examples: + +regexp_like('Hello World', 'world') false +regexp_like('Hello World', 'world', 'i') true + + + + + The regexp_match function returns a text array of + matching substring(s) within the first match of a POSIX + regular expression pattern to a string. It has the syntax + regexp_match(string, + pattern , flags ). + If there is no match, the result is NULL. + If a match is found, and the pattern contains no + parenthesized subexpressions, then the result is a single-element text + array containing the substring matching the whole pattern. + If a match is found, and the pattern contains + parenthesized subexpressions, then the result is a text array + whose n'th element is the substring matching + the n'th parenthesized subexpression of + the pattern (not counting non-capturing + parentheses; see below for details). + The flags parameter is an optional text string + containing zero or more single-letter flags that change the function's + behavior. Supported flags are described + in . + + + + Some examples: + +SELECT regexp_match('foobarbequebaz', 'bar.*que'); + regexp_match +-------------- + {barbeque} +(1 row) + +SELECT regexp_match('foobarbequebaz', '(bar)(beque)'); + regexp_match +-------------- + {bar,beque} +(1 row) + + + + + + In the common case where you just want the whole matching substring + or NULL for no match, the best solution is to + use regexp_substr(). + However, regexp_substr() only exists + in PostgreSQL version 15 and up. When + working in older versions, you can extract the first element + of regexp_match()'s result, for example: + +SELECT (regexp_match('foobarbequebaz', 'bar.*que'))[1]; + regexp_match +-------------- + barbeque +(1 row) + + + + + + The regexp_matches function returns a set of text arrays + of matching substring(s) within matches of a POSIX regular + expression pattern to a string. It has the same syntax as + regexp_match. + This function returns no rows if there is no match, one row if there is + a match and the g flag is not given, or N + rows if there are N matches and the g flag + is given. Each returned row is a text array containing the whole + matched substring or the substrings matching parenthesized + subexpressions of the pattern, just as described above + for regexp_match. + regexp_matches accepts all the flags shown + in , plus + the g flag which commands it to return all matches, not + just the first one. + + + + Some examples: + +SELECT regexp_matches('foo', 'not there'); + regexp_matches +---------------- +(0 rows) + +SELECT regexp_matches('foobarbequebazilbarfbonk', '(b[^b]+)(b[^b]+)', 'g'); + regexp_matches +---------------- + {bar,beque} + {bazil,barf} +(2 rows) + + + + + + In most cases regexp_matches() should be used with + the g flag, since if you only want the first match, it's + easier and more efficient to use regexp_match(). + However, regexp_match() only exists + in PostgreSQL version 10 and up. When working in older + versions, a common trick is to place a regexp_matches() + call in a sub-select, for example: + +SELECT col1, (SELECT regexp_matches(col2, '(bar)(beque)')) FROM tab; + + This produces a text array if there's a match, or NULL if + not, the same as regexp_match() would do. Without the + sub-select, this query would produce no output at all for table rows + without a match, which is typically not the desired behavior. + + + + + The regexp_replace function provides substitution of + new text for substrings that match POSIX regular expression patterns. + It has the syntax + regexp_replace(string, + pattern, replacement + , flags ) + or + regexp_replace(string, + pattern, replacement, + start + , N + , flags ). + The source string is returned unchanged if + there is no match to the pattern. If there is a + match, the string is returned with the + replacement string substituted for the matching + substring. The replacement string can contain + \n, where n is 1 + through 9, to indicate that the source substring matching the + n'th parenthesized subexpression of the pattern should be + inserted, and it can contain \& to indicate that the + substring matching the entire pattern should be inserted. Write + \\ if you need to put a literal backslash in the replacement + text. + pattern is searched for + in string, normally from the beginning of + the string, but if the start parameter is + provided then beginning from that character index. + By default, only the first match of the pattern is replaced. + If N is specified and is greater than zero, + then the N'th match of the pattern + is replaced. + If the g flag is given, or + if N is specified and is zero, then all + matches at or after the start position are + replaced. (The g flag is ignored + when N is specified.) + The flags parameter is an optional text + string containing zero or more single-letter flags that change the + function's behavior. Supported flags (though + not g) are + described in . + + + + Some examples: + +regexp_replace('foobarbaz', 'b..', 'X') + fooXbaz +regexp_replace('foobarbaz', 'b..', 'X', 'g') + fooXX +regexp_replace('foobarbaz', 'b(..)', 'X\1Y', 'g') + fooXarYXazY +regexp_replace('A PostgreSQL function', 'a|e|i|o|u', 'X', 1, 0, 'i') + X PXstgrXSQL fXnctXXn +regexp_replace(string=>'A PostgreSQL function', pattern=>'a|e|i|o|u', replacement=>'X', start=>1, "N"=>3, flags=>'i') + A PostgrXSQL function + + + + + The regexp_split_to_table function splits a string using a POSIX + regular expression pattern as a delimiter. It has the syntax + regexp_split_to_table(string, pattern + , flags ). + If there is no match to the pattern, the function returns the + string. If there is at least one match, for each match it returns + the text from the end of the last match (or the beginning of the string) + to the beginning of the match. When there are no more matches, it + returns the text from the end of the last match to the end of the string. + The flags parameter is an optional text string containing + zero or more single-letter flags that change the function's behavior. + regexp_split_to_table supports the flags described in + . + + + + The regexp_split_to_array function behaves the same as + regexp_split_to_table, except that regexp_split_to_array + returns its result as an array of text. It has the syntax + regexp_split_to_array(string, pattern + , flags ). + The parameters are the same as for regexp_split_to_table. + + + + Some examples: + +SELECT foo FROM regexp_split_to_table('the quick brown fox jumps over the lazy dog', '\s+') AS foo; + foo +------- + the + quick + brown + fox + jumps + over + the + lazy + dog +(9 rows) + +SELECT regexp_split_to_array('the quick brown fox jumps over the lazy dog', '\s+'); + regexp_split_to_array +----------------------------------------------- + {the,quick,brown,fox,jumps,over,the,lazy,dog} +(1 row) + +SELECT foo FROM regexp_split_to_table('the quick brown fox', '\s*') AS foo; + foo +----- + t + h + e + q + u + i + c + k + b + r + o + w + n + f + o + x +(16 rows) + + + + + As the last example demonstrates, the regexp split functions ignore + zero-length matches that occur at the start or end of the string + or immediately after a previous match. This is contrary to the strict + definition of regexp matching that is implemented by + the other regexp functions, but is usually the most convenient behavior + in practice. Other software systems such as Perl use similar definitions. + + + + The regexp_substr function returns the substring + that matches a POSIX regular expression pattern, + or NULL if there is no match. It has the syntax + regexp_substr(string, + pattern + , start + , N + , flags + , subexpr + ). + pattern is searched for + in string, normally from the beginning of + the string, but if the start parameter is + provided then beginning from that character index. + If N is specified + then the N'th match of the pattern + is returned, otherwise the first match is returned. + The flags parameter is an optional text + string containing zero or more single-letter flags that change the + function's behavior. Supported flags are described + in . + For a pattern containing parenthesized + subexpressions, subexpr is an integer + indicating which subexpression is of interest: the result is the + substring matching that subexpression. + Subexpressions are numbered in the order of their leading parentheses. + When subexpr is omitted or zero, the result + is the whole match regardless of parenthesized subexpressions. + + + + Some examples: + +regexp_substr('number of your street, town zip, FR', '[^,]+', 1, 2) + town zip +regexp_substr('ABCDEFGHI', '(c..)(...)', 1, 1, 'i', 2) + FGH + + + + + + + Regular Expression Details + + + PostgreSQL's regular expressions are implemented + using a software package written by Henry Spencer. Much of + the description of regular expressions below is copied verbatim from his + manual. + + + + Regular expressions (REs), as defined in + POSIX 1003.2, come in two forms: + extended REs or EREs + (roughly those of egrep), and + basic REs or BREs + (roughly those of ed). + PostgreSQL supports both forms, and + also implements some extensions + that are not in the POSIX standard, but have become widely used + due to their availability in programming languages such as Perl and Tcl. + REs using these non-POSIX extensions are called + advanced REs or AREs + in this documentation. AREs are almost an exact superset of EREs, + but BREs have several notational incompatibilities (as well as being + much more limited). + We first describe the ARE and ERE forms, noting features that apply + only to AREs, and then describe how BREs differ. + + + + + PostgreSQL always initially presumes that a regular + expression follows the ARE rules. However, the more limited ERE or + BRE rules can be chosen by prepending an embedded option + to the RE pattern, as described in . + This can be useful for compatibility with applications that expect + exactly the POSIX 1003.2 rules. + + + + + A regular expression is defined as one or more + branches, separated by + |. It matches anything that matches one of the + branches. + + + + A branch is zero or more quantified atoms or + constraints, concatenated. + It matches a match for the first, followed by a match for the second, etc.; + an empty branch matches the empty string. + + + + A quantified atom is an atom possibly followed + by a single quantifier. + Without a quantifier, it matches a match for the atom. + With a quantifier, it can match some number of matches of the atom. + An atom can be any of the possibilities + shown in . + The possible quantifiers and their meanings are shown in + . + + + + A constraint matches an empty string, but matches only when + specific conditions are met. A constraint can be used where an atom + could be used, except it cannot be followed by a quantifier. + The simple constraints are shown in + ; + some more constraints are described later. + + + + + Regular Expression Atoms + + + + + Atom + Description + + + + + + (re) + (where re is any regular expression) + matches a match for + re, with the match noted for possible reporting + + + + (?:re) + as above, but the match is not noted for reporting + (a non-capturing set of parentheses) + (AREs only) + + + + . + matches any single character + + + + [chars] + a bracket expression, + matching any one of the chars (see + for more detail) + + + + \k + (where k is a non-alphanumeric character) + matches that character taken as an ordinary character, + e.g., \\ matches a backslash character + + + + \c + where c is alphanumeric + (possibly followed by other characters) + is an escape, see + (AREs only; in EREs and BREs, this matches c) + + + + { + when followed by a character other than a digit, + matches the left-brace character {; + when followed by a digit, it is the beginning of a + bound (see below) + + + + x + where x is a single character with no other + significance, matches that character + + + +

+ + + An RE cannot end with a backslash (\). + + + + + If you have turned off, + any backslashes you write in literal string constants will need to be + doubled. See for more information. + + + + + Regular Expression Quantifiers + + + + + Quantifier + Matches + + + + + + * + a sequence of 0 or more matches of the atom + + + + + + a sequence of 1 or more matches of the atom + + + + ? + a sequence of 0 or 1 matches of the atom + + + + {m} + a sequence of exactly m matches of the atom + + + + {m,} + a sequence of m or more matches of the atom + + + + + {m,n} + a sequence of m through n + (inclusive) matches of the atom; m cannot exceed + n + + + + *? + non-greedy version of * + + + + +? + non-greedy version of + + + + + ?? + non-greedy version of ? + + + + {m}? + non-greedy version of {m} + + + + {m,}? + non-greedy version of {m,} + + + + + {m,n}? + non-greedy version of {m,n} + + + +

+ + + The forms using {...} + are known as bounds. + The numbers m and n within a bound are + unsigned decimal integers with permissible values from 0 to 255 inclusive. + + + + Non-greedy quantifiers (available in AREs only) match the + same possibilities as their corresponding normal (greedy) + counterparts, but prefer the smallest number rather than the largest + number of matches. + See for more detail. + + + + + A quantifier cannot immediately follow another quantifier, e.g., + ** is invalid. + A quantifier cannot + begin an expression or subexpression or follow + ^ or |. + + + + + Regular Expression Constraints + + + + + Constraint + Description + + + + + + ^ + matches at the beginning of the string + + + + $ + matches at the end of the string + + + + (?=re) + positive lookahead matches at any point + where a substring matching re begins + (AREs only) + + + + (?!re) + negative lookahead matches at any point + where no substring matching re begins + (AREs only) + + + + (?<=re) + positive lookbehind matches at any point + where a substring matching re ends + (AREs only) + + + + (?<!re) + negative lookbehind matches at any point + where no substring matching re ends + (AREs only) + + + +

+ + + Lookahead and lookbehind constraints cannot contain back + references (see ), + and all parentheses within them are considered non-capturing. + + + + + Bracket Expressions + + + A bracket expression is a list of + characters enclosed in []. It normally matches + any single character from the list (but see below). If the list + begins with ^, it matches any single character + not from the rest of the list. + If two characters + in the list are separated by -, this is + shorthand for the full range of characters between those two + (inclusive) in the collating sequence, + e.g., [0-9] in ASCII matches + any decimal digit. It is illegal for two ranges to share an + endpoint, e.g., a-c-e. Ranges are very + collating-sequence-dependent, so portable programs should avoid + relying on them. + + + + To include a literal ] in the list, make it the + first character (after ^, if that is used). To + include a literal -, make it the first or last + character, or the second endpoint of a range. To use a literal + - as the first endpoint of a range, enclose it + in [. and .] to make it a + collating element (see below). With the exception of these characters, + some combinations using [ + (see next paragraphs), and escapes (AREs only), all other special + characters lose their special significance within a bracket expression. + In particular, \ is not special when following + ERE or BRE rules, though it is special (as introducing an escape) + in AREs. + + + + Within a bracket expression, a collating element (a character, a + multiple-character sequence that collates as if it were a single + character, or a collating-sequence name for either) enclosed in + [. and .] stands for the + sequence of characters of that collating element. The sequence is + treated as a single element of the bracket expression's list. This + allows a bracket + expression containing a multiple-character collating element to + match more than one character, e.g., if the collating sequence + includes a ch collating element, then the RE + [[.ch.]]*c matches the first five characters of + chchcc. + + + + + PostgreSQL currently does not support multi-character collating + elements. This information describes possible future behavior. + + + + + Within a bracket expression, a collating element enclosed in + [= and =] is an equivalence + class, standing for the sequences of characters of all collating + elements equivalent to that one, including itself. (If there are + no other equivalent collating elements, the treatment is as if the + enclosing delimiters were [. and + .].) For example, if o and + ^ are the members of an equivalence class, then + [[=o=]], [[=^=]], and + [o^] are all synonymous. An equivalence class + cannot be an endpoint of a range. + + + + Within a bracket expression, the name of a character class + enclosed in [: and :] stands + for the list of all characters belonging to that class. A character + class cannot be used as an endpoint of a range. + The POSIX standard defines these character class + names: + alnum (letters and numeric digits), + alpha (letters), + blank (space and tab), + cntrl (control characters), + digit (numeric digits), + graph (printable characters except space), + lower (lower-case letters), + print (printable characters including space), + punct (punctuation), + space (any white space), + upper (upper-case letters), + and xdigit (hexadecimal digits). + The behavior of these standard character classes is generally + consistent across platforms for characters in the 7-bit ASCII set. + Whether a given non-ASCII character is considered to belong to one + of these classes depends on the collation + that is used for the regular-expression function or operator + (see ), or by default on the + database's LC_CTYPE locale setting (see + ). The classification of non-ASCII + characters can vary across platforms even in similarly-named + locales. (But the C locale never considers any + non-ASCII characters to belong to any of these classes.) + In addition to these standard character + classes, PostgreSQL defines + the word character class, which is the same as + alnum plus the underscore (_) + character, and + the ascii character class, which contains exactly + the 7-bit ASCII set. + + + + There are two special cases of bracket expressions: the bracket + expressions [[:<:]] and + [[:>:]] are constraints, + matching empty strings at the beginning + and end of a word respectively. A word is defined as a sequence + of word characters that is neither preceded nor followed by word + characters. A word character is any character belonging to the + word character class, that is, any letter, digit, + or underscore. This is an extension, compatible with but not + specified by POSIX 1003.2, and should be used with + caution in software intended to be portable to other systems. + The constraint escapes described below are usually preferable; they + are no more standard, but are easier to type. + + + + + Regular Expression Escapes + + + Escapes are special sequences beginning with \ + followed by an alphanumeric character. Escapes come in several varieties: + character entry, class shorthands, constraint escapes, and back references. + A \ followed by an alphanumeric character but not constituting + a valid escape is illegal in AREs. + In EREs, there are no escapes: outside a bracket expression, + a \ followed by an alphanumeric character merely stands for + that character as an ordinary character, and inside a bracket expression, + \ is an ordinary character. + (The latter is the one actual incompatibility between EREs and AREs.) + + + + Character-entry escapes exist to make it easier to specify + non-printing and other inconvenient characters in REs. They are + shown in . + + + + Class-shorthand escapes provide shorthands for certain + commonly-used character classes. They are + shown in . + + + + A constraint escape is a constraint, + matching the empty string if specific conditions are met, + written as an escape. They are + shown in . + + + + A back reference (\n) matches the + same string matched by the previous parenthesized subexpression specified + by the number n + (see ). For example, + ([bc])\1 matches bb or cc + but not bc or cb. + The subexpression must entirely precede the back reference in the RE. + Subexpressions are numbered in the order of their leading parentheses. + Non-capturing parentheses do not define subexpressions. + The back reference considers only the string characters matched by the + referenced subexpression, not any constraints contained in it. For + example, (^\d)\1 will match 22. + + + + Regular Expression Character-Entry Escapes + + + + + Escape + Description + + + + + + \a + alert (bell) character, as in C + + + + \b + backspace, as in C + + + + \B + synonym for backslash (\) to help reduce the need for backslash + doubling + + + + \cX + (where X is any character) the character whose + low-order 5 bits are the same as those of + X, and whose other bits are all zero + + + + \e + the character whose collating-sequence name + is ESC, + or failing that, the character with octal value 033 + + + + \f + form feed, as in C + + + + \n + newline, as in C + + + + \r + carriage return, as in C + + + + \t + horizontal tab, as in C + + + + \uwxyz + (where wxyz is exactly four hexadecimal digits) + the character whose hexadecimal value is + 0xwxyz + + + + + \Ustuvwxyz + (where stuvwxyz is exactly eight hexadecimal + digits) + the character whose hexadecimal value is + 0xstuvwxyz + + + + + \v + vertical tab, as in C + + + + \xhhh + (where hhh is any sequence of hexadecimal + digits) + the character whose hexadecimal value is + 0xhhh + (a single character no matter how many hexadecimal digits are used) + + + + + \0 + the character whose value is 0 (the null byte) + + + + \xy + (where xy is exactly two octal digits, + and is not a back reference) + the character whose octal value is + 0xy + + + + \xyz + (where xyz is exactly three octal digits, + and is not a back reference) + the character whose octal value is + 0xyz + + + +

+ + + Hexadecimal digits are 0-9, + a-f, and A-F. + Octal digits are 0-7. + + + + Numeric character-entry escapes specifying values outside the ASCII range + (0–127) have meanings dependent on the database encoding. When the + encoding is UTF-8, escape values are equivalent to Unicode code points, + for example \u1234 means the character U+1234. + For other multibyte encodings, character-entry escapes usually just + specify the concatenation of the byte values for the character. If the + escape value does not correspond to any legal character in the database + encoding, no error will be raised, but it will never match any data. + + + + The character-entry escapes are always taken as ordinary characters. + For example, \135 is ] in ASCII, but + \135 does not terminate a bracket expression. + + + + Regular Expression Class-Shorthand Escapes + + + + + Escape + Description + + + + + + \d + matches any digit, like + [[:digit:]] + + + + \s + matches any whitespace character, like + [[:space:]] + + + + \w + matches any word character, like + [[:word:]] + + + + \D + matches any non-digit, like + [^[:digit:]] + + + + \S + matches any non-whitespace character, like + [^[:space:]] + + + + \W + matches any non-word character, like + [^[:word:]] + + + +

+ + + The class-shorthand escapes also work within bracket expressions, + although the definitions shown above are not quite syntactically + valid in that context. + For example, [a-c\d] is equivalent to + [a-c[:digit:]]. + + + + Regular Expression Constraint Escapes + + + + + Escape + Description + + + + + + \A + matches only at the beginning of the string + (see for how this differs from + ^) + + + + \m + matches only at the beginning of a word + + + + \M + matches only at the end of a word + + + + \y + matches only at the beginning or end of a word + + + + \Y + matches only at a point that is not the beginning or end of a + word + + + + \Z + matches only at the end of the string + (see for how this differs from + $) + + + +

+ + + A word is defined as in the specification of + [[:<:]] and [[:>:]] above. + Constraint escapes are illegal within bracket expressions. + + + + Regular Expression Back References + + + + + Escape + Description + + + + + + \m + (where m is a nonzero digit) + a back reference to the m'th subexpression + + + + \mnn + (where m is a nonzero digit, and + nn is some more digits, and the decimal value + mnn is not greater than the number of closing capturing + parentheses seen so far) + a back reference to the mnn'th subexpression + + + +

+ + + + There is an inherent ambiguity between octal character-entry + escapes and back references, which is resolved by the following heuristics, + as hinted at above. + A leading zero always indicates an octal escape. + A single non-zero digit, not followed by another digit, + is always taken as a back reference. + A multi-digit sequence not starting with a zero is taken as a back + reference if it comes after a suitable subexpression + (i.e., the number is in the legal range for a back reference), + and otherwise is taken as octal. + + + + + + Regular Expression Metasyntax + + + In addition to the main syntax described above, there are some special + forms and miscellaneous syntactic facilities available. + + + + An RE can begin with one of two special director prefixes. + If an RE begins with ***:, + the rest of the RE is taken as an ARE. (This normally has no effect in + PostgreSQL, since REs are assumed to be AREs; + but it does have an effect if ERE or BRE mode had been specified by + the flags parameter to a regex function.) + If an RE begins with ***=, + the rest of the RE is taken to be a literal string, + with all characters considered ordinary characters. + + + + An ARE can begin with embedded options: + a sequence (?xyz) + (where xyz is one or more alphabetic characters) + specifies options affecting the rest of the RE. + These options override any previously determined options — + in particular, they can override the case-sensitivity behavior implied by + a regex operator, or the flags parameter to a regex + function. + The available option letters are + shown in . + Note that these same option letters are used in the flags + parameters of regex functions. + + + + ARE Embedded-Option Letters + + + + + Option + Description + + + + + + b + rest of RE is a BRE + + + + c + case-sensitive matching (overrides operator type) + + + + e + rest of RE is an ERE + + + + i + case-insensitive matching (see + ) (overrides operator type) + + + + m + historical synonym for n + + + + n + newline-sensitive matching (see + ) + + + + p + partial newline-sensitive matching (see + ) + + + + q + rest of RE is a literal (quoted) string, all ordinary + characters + + + + s + non-newline-sensitive matching (default) + + + + t + tight syntax (default; see below) + + + + w + inverse partial newline-sensitive (weird) matching + (see ) + + + + x + expanded syntax (see below) + + + +

+ + + Embedded options take effect at the ) terminating the sequence. + They can appear only at the start of an ARE (after the + ***: director if any). + + + + In addition to the usual (tight) RE syntax, in which all + characters are significant, there is an expanded syntax, + available by specifying the embedded x option. + In the expanded syntax, + white-space characters in the RE are ignored, as are + all characters between a # + and the following newline (or the end of the RE). This + permits paragraphing and commenting a complex RE. + There are three exceptions to that basic rule: + + + + + a white-space character or # preceded by \ is + retained + + + + + white space or # within a bracket expression is retained + + + + + white space and comments cannot appear within multi-character symbols, + such as (?: + + + + + For this purpose, white-space characters are blank, tab, newline, and + any character that belongs to the space character class. + + + + Finally, in an ARE, outside bracket expressions, the sequence + (?#ttt) + (where ttt is any text not containing a )) + is a comment, completely ignored. + Again, this is not allowed between the characters of + multi-character symbols, like (?:. + Such comments are more a historical artifact than a useful facility, + and their use is deprecated; use the expanded syntax instead. + + + + None of these metasyntax extensions is available if + an initial ***= director + has specified that the user's input be treated as a literal string + rather than as an RE. + + + + + Regular Expression Matching Rules + + + In the event that an RE could match more than one substring of a given + string, the RE matches the one starting earliest in the string. + If the RE could match more than one substring starting at that point, + either the longest possible match or the shortest possible match will + be taken, depending on whether the RE is greedy or + non-greedy. + + + + Whether an RE is greedy or not is determined by the following rules: + + + + Most atoms, and all constraints, have no greediness attribute (because + they cannot match variable amounts of text anyway). + + + + + Adding parentheses around an RE does not change its greediness. + + + + + A quantified atom with a fixed-repetition quantifier + ({m} + or + {m}?) + has the same greediness (possibly none) as the atom itself. + + + + + A quantified atom with other normal quantifiers (including + {m,n} + with m equal to n) + is greedy (prefers longest match). + + + + + A quantified atom with a non-greedy quantifier (including + {m,n}? + with m equal to n) + is non-greedy (prefers shortest match). + + + + + A branch — that is, an RE that has no top-level + | operator — has the same greediness as the first + quantified atom in it that has a greediness attribute. + + + + + An RE consisting of two or more branches connected by the + | operator is always greedy. + + + + + + + The above rules associate greediness attributes not only with individual + quantified atoms, but with branches and entire REs that contain quantified + atoms. What that means is that the matching is done in such a way that + the branch, or whole RE, matches the longest or shortest possible + substring as a whole. Once the length of the entire match + is determined, the part of it that matches any particular subexpression + is determined on the basis of the greediness attribute of that + subexpression, with subexpressions starting earlier in the RE taking + priority over ones starting later. + + + + An example of what this means: + +SELECT SUBSTRING('XY1234Z', 'Y*([0-9]{1,3})'); +Result: 123 +SELECT SUBSTRING('XY1234Z', 'Y*?([0-9]{1,3})'); +Result: 1 + + In the first case, the RE as a whole is greedy because Y* + is greedy. It can match beginning at the Y, and it matches + the longest possible string starting there, i.e., Y123. + The output is the parenthesized part of that, or 123. + In the second case, the RE as a whole is non-greedy because Y*? + is non-greedy. It can match beginning at the Y, and it matches + the shortest possible string starting there, i.e., Y1. + The subexpression [0-9]{1,3} is greedy but it cannot change + the decision as to the overall match length; so it is forced to match + just 1. + + + + In short, when an RE contains both greedy and non-greedy subexpressions, + the total match length is either as long as possible or as short as + possible, according to the attribute assigned to the whole RE. The + attributes assigned to the subexpressions only affect how much of that + match they are allowed to eat relative to each other. + + + + The quantifiers {1,1} and {1,1}? + can be used to force greediness or non-greediness, respectively, + on a subexpression or a whole RE. + This is useful when you need the whole RE to have a greediness attribute + different from what's deduced from its elements. As an example, + suppose that we are trying to separate a string containing some digits + into the digits and the parts before and after them. We might try to + do that like this: + +SELECT regexp_match('abc01234xyz', '(.*)(\d+)(.*)'); +Result: {abc0123,4,xyz} + + That didn't work: the first .* is greedy so + it eats as much as it can, leaving the \d+ to + match at the last possible place, the last digit. We might try to fix + that by making it non-greedy: + +SELECT regexp_match('abc01234xyz', '(.*?)(\d+)(.*)'); +Result: {abc,0,""} + + That didn't work either, because now the RE as a whole is non-greedy + and so it ends the overall match as soon as possible. We can get what + we want by forcing the RE as a whole to be greedy: + +SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}'); +Result: {abc,01234,xyz} + + Controlling the RE's overall greediness separately from its components' + greediness allows great flexibility in handling variable-length patterns. + + + + When deciding what is a longer or shorter match, + match lengths are measured in characters, not collating elements. + An empty string is considered longer than no match at all. + For example: + bb* + matches the three middle characters of abbbc; + (week|wee)(night|knights) + matches all ten characters of weeknights; + when (.*).* + is matched against abc the parenthesized subexpression + matches all three characters; and when + (a*)* is matched against bc + both the whole RE and the parenthesized + subexpression match an empty string. + + + + If case-independent matching is specified, + the effect is much as if all case distinctions had vanished from the + alphabet. + When an alphabetic that exists in multiple cases appears as an + ordinary character outside a bracket expression, it is effectively + transformed into a bracket expression containing both cases, + e.g., x becomes [xX]. + When it appears inside a bracket expression, all case counterparts + of it are added to the bracket expression, e.g., + [x] becomes [xX] + and [^x] becomes [^xX]. + + + + If newline-sensitive matching is specified, . + and bracket expressions using ^ + will never match the newline character + (so that matches will not cross lines unless the RE + explicitly includes a newline) + and ^ and $ + will match the empty string after and before a newline + respectively, in addition to matching at beginning and end of string + respectively. + But the ARE escapes \A and \Z + continue to match beginning or end of string only. + Also, the character class shorthands \D + and \W will match a newline regardless of this mode. + (Before PostgreSQL 14, they did not match + newlines when in newline-sensitive mode. + Write [^[:digit:]] + or [^[:word:]] to get the old behavior.) + + + + If partial newline-sensitive matching is specified, + this affects . and bracket expressions + as with newline-sensitive matching, but not ^ + and $. + + + + If inverse partial newline-sensitive matching is specified, + this affects ^ and $ + as with newline-sensitive matching, but not . + and bracket expressions. + This isn't very useful but is provided for symmetry. + + + + + Limits and Compatibility + + + No particular limit is imposed on the length of REs in this + implementation. However, + programs intended to be highly portable should not employ REs longer + than 256 bytes, + as a POSIX-compliant implementation can refuse to accept such REs. + + + + The only feature of AREs that is actually incompatible with + POSIX EREs is that \ does not lose its special + significance inside bracket expressions. + All other ARE features use syntax which is illegal or has + undefined or unspecified effects in POSIX EREs; + the *** syntax of directors likewise is outside the POSIX + syntax for both BREs and EREs. + + + + Many of the ARE extensions are borrowed from Perl, but some have + been changed to clean them up, and a few Perl extensions are not present. + Incompatibilities of note include \b, \B, + the lack of special treatment for a trailing newline, + the addition of complemented bracket expressions to the things + affected by newline-sensitive matching, + the restrictions on parentheses and back references in lookahead/lookbehind + constraints, and the longest/shortest-match (rather than first-match) + matching semantics. + + + + + Basic Regular Expressions + + + BREs differ from EREs in several respects. + In BREs, |, +, and ? + are ordinary characters and there is no equivalent + for their functionality. + The delimiters for bounds are + \{ and \}, + with { and } + by themselves ordinary characters. + The parentheses for nested subexpressions are + $ and $, + with ( and ) by themselves ordinary characters. + ^ is an ordinary character except at the beginning of the + RE or the beginning of a parenthesized subexpression, + $ is an ordinary character except at the end of the + RE or the end of a parenthesized subexpression, + and * is an ordinary character if it appears at the beginning + of the RE or the beginning of a parenthesized subexpression + (after a possible leading ^). + Finally, single-digit back references are available, and + \< and \> + are synonyms for + [[:<:]] and [[:>:]] + respectively; no other escapes are available in BREs. + + + + + + + Differences from SQL Standard and XQuery + + + LIKE_REGEX + + + + OCCURRENCES_REGEX + + + + POSITION_REGEX + + + + SUBSTRING_REGEX + + + + TRANSLATE_REGEX + + + + XQuery regular expressions + + + + Since SQL:2008, the SQL standard includes regular expression operators + and functions that performs pattern + matching according to the XQuery regular expression + standard: + + LIKE_REGEX + OCCURRENCES_REGEX + POSITION_REGEX + SUBSTRING_REGEX + TRANSLATE_REGEX + + PostgreSQL does not currently implement these + operators and functions. You can get approximately equivalent + functionality in each case as shown in . (Various optional clauses on + both sides have been omitted in this table.) + + + + Regular Expression Functions Equivalencies + + + + + SQL standard + PostgreSQL + + + + + + string LIKE_REGEX pattern + regexp_like(string, pattern) or string ~ pattern + + + + OCCURRENCES_REGEX(pattern IN string) + regexp_count(string, pattern) + + + + POSITION_REGEX(pattern IN string) + regexp_instr(string, pattern) + + + + SUBSTRING_REGEX(pattern IN string) + regexp_substr(string, pattern) + + + + TRANSLATE_REGEX(pattern IN string WITH replacement) + regexp_replace(string, pattern, replacement) + + + +

+ + + Regular expression functions similar to those provided by PostgreSQL are + also available in a number of other SQL implementations, whereas the + SQL-standard functions are not as widely implemented. Some of the + details of the regular expression syntax will likely differ in each + implementation. + + + + The SQL-standard operators and functions use XQuery regular expressions, + which are quite close to the ARE syntax described above. + Notable differences between the existing POSIX-based + regular-expression feature and XQuery regular expressions include: + + + + + XQuery character class subtraction is not supported. An example of + this feature is using the following to match only English + consonants: [a-z-[aeiou]]. + + + + + XQuery character class shorthands \c, + \C, \i, + and \I are not supported. + + + + + XQuery character class elements + using \p{UnicodeProperty} or the + inverse \P{UnicodeProperty} are not supported. + + + + + POSIX interprets character classes such as \w + (see ) + according to the prevailing locale (which you can control by + attaching a COLLATE clause to the operator or + function). XQuery specifies these classes by reference to Unicode + character properties, so equivalent behavior is obtained only with + a locale that follows the Unicode rules. + + + + + The SQL standard (not XQuery itself) attempts to cater for more + variants of newline than POSIX does. The + newline-sensitive matching options described above consider only + ASCII NL (\n) to be a newline, but SQL would have + us treat CR (\r), CRLF (\r\n) + (a Windows-style newline), and some Unicode-only characters like + LINE SEPARATOR (U+2028) as newlines as well. + Notably, . and \s should + count \r\n as one character not two according to + SQL. + + + + + Of the character-entry escapes described in + , + XQuery supports only \n, \r, + and \t. + + + + + XQuery does not support + the [:name:] syntax + for character classes within bracket expressions. + + + + + XQuery does not have lookahead or lookbehind constraints, + nor any of the constraint escapes described in + . + + + + + The metasyntax forms described in + do not exist in XQuery. + + + + + The regular expression flag letters defined by XQuery are + related to but not the same as the option letters for POSIX + (). While the + i and q options behave the + same, others do not: + + + + XQuery's s (allow dot to match newline) + and m (allow ^ + and $ to match at newlines) flags provide + access to the same behaviors as + POSIX's n, p + and w flags, but they + do not match the behavior of + POSIX's s and m flags. + Note in particular that dot-matches-newline is the default + behavior in POSIX but not XQuery. + + + + + XQuery's x (ignore whitespace in pattern) flag + is noticeably different from POSIX's expanded-mode flag. + POSIX's x flag also + allows # to begin a comment in the pattern, + and POSIX will not ignore a whitespace character after a + backslash. + + + + + + + + + + + diff --git a/doc/src/sgml/func/func-math.sgml b/doc/src/sgml/func/func-math.sgml new file mode 100644 index 00000000000..7528dc4cea4 --- /dev/null +++ b/doc/src/sgml/func/func-math.sgml @@ -0,0 +1,1615 @@ + + Mathematical Functions and Operators + + + Mathematical operators are provided for many + PostgreSQL types. For types without + standard mathematical conventions + (e.g., date/time types) we + describe the actual behavior in subsequent sections. + + + + shows the mathematical + operators that are available for the standard numeric types. + Unless otherwise noted, operators shown as + accepting numeric_type are available for all + the types smallint, integer, + bigint, numeric, real, + and double precision. + Operators shown as accepting integral_type + are available for the types smallint, integer, + and bigint. + Except where noted, each form of an operator returns the same data type + as its argument(s). Calls involving multiple argument data types, such + as integer + numeric, + are resolved by using the type appearing later in these lists. + + + + Mathematical Operators + + + + + + Operator + + + Description + + + Example(s) + + + + + + + + numeric_type + numeric_type + numeric_type + + + Addition + + + 2 + 3 + 5 + + + + + + + numeric_type + numeric_type + + + Unary plus (no operation) + + + + 3.5 + 3.5 + + + + + + numeric_type - numeric_type + numeric_type + + + Subtraction + + + 2 - 3 + -1 + + + + + + - numeric_type + numeric_type + + + Negation + + + - (-4) + 4 + + + + + + numeric_type * numeric_type + numeric_type + + + Multiplication + + + 2 * 3 + 6 + + + + + + numeric_type / numeric_type + numeric_type + + + Division (for integral types, division truncates the result towards + zero) + + + 5.0 / 2 + 2.5000000000000000 + + + 5 / 2 + 2 + + + (-5) / 2 + -2 + + + + + + numeric_type % numeric_type + numeric_type + + + Modulo (remainder); available for smallint, + integer, bigint, and numeric + + + 5 % 4 + 1 + + + + + + numeric ^ numeric + numeric + + + double precision ^ double precision + double precision + + + Exponentiation + + + 2 ^ 3 + 8 + + + Unlike typical mathematical practice, multiple uses of + ^ will associate left to right by default: + + + 2 ^ 3 ^ 3 + 512 + + + 2 ^ (3 ^ 3) + 134217728 + + + + + + |/ double precision + double precision + + + Square root + + + |/ 25.0 + 5 + + + + + + ||/ double precision + double precision + + + Cube root + + + ||/ 64.0 + 4 + + + + + + @ numeric_type + numeric_type + + + Absolute value + + + @ -5.0 + 5.0 + + + + + + integral_type & integral_type + integral_type + + + Bitwise AND + + + 91 & 15 + 11 + + + + + + integral_type | integral_type + integral_type + + + Bitwise OR + + + 32 | 3 + 35 + + + + + + integral_type # integral_type + integral_type + + + Bitwise exclusive OR + + + 17 # 5 + 20 + + + + + + ~ integral_type + integral_type + + + Bitwise NOT + + + ~1 + -2 + + + + + + integral_type << integer + integral_type + + + Bitwise shift left + + + 1 << 4 + 16 + + + + + + integral_type >> integer + integral_type + + + Bitwise shift right + + + 8 >> 2 + 2 + + + + + +

+ + + shows the available + mathematical functions. + Many of these functions are provided in multiple forms with different + argument types. + Except where noted, any given form of a function returns the same + data type as its argument(s); cross-type cases are resolved in the + same way as explained above for operators. + The functions working with double precision data are mostly + implemented on top of the host system's C library; accuracy and behavior in + boundary cases can therefore vary depending on the host system. + + + + Mathematical Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + abs + + abs ( numeric_type ) + numeric_type + + + Absolute value + + + abs(-17.4) + 17.4 + + + + + + + cbrt + + cbrt ( double precision ) + double precision + + + Cube root + + + cbrt(64.0) + 4 + + + + + + + ceil + + ceil ( numeric ) + numeric + + + ceil ( double precision ) + double precision + + + Nearest integer greater than or equal to argument + + + ceil(42.2) + 43 + + + ceil(-42.8) + -42 + + + + + + + ceiling + + ceiling ( numeric ) + numeric + + + ceiling ( double precision ) + double precision + + + Nearest integer greater than or equal to argument (same + as ceil) + + + ceiling(95.3) + 96 + + + + + + + degrees + + degrees ( double precision ) + double precision + + + Converts radians to degrees + + + degrees(0.5) + 28.64788975654116 + + + + + + + div + + div ( y numeric, + x numeric ) + numeric + + + Integer quotient of y/x + (truncates towards zero) + + + div(9, 4) + 2 + + + + + + + erf + + erf ( double precision ) + double precision + + + Error function + + + erf(1.0) + 0.8427007929497149 + + + + + + + erfc + + erfc ( double precision ) + double precision + + + Complementary error function (1 - erf(x), without + loss of precision for large inputs) + + + erfc(1.0) + 0.15729920705028513 + + + + + + + exp + + exp ( numeric ) + numeric + + + exp ( double precision ) + double precision + + + Exponential (e raised to the given power) + + + exp(1.0) + 2.7182818284590452 + + + + + + + factorial + + factorial ( bigint ) + numeric + + + Factorial + + + factorial(5) + 120 + + + + + + + floor + + floor ( numeric ) + numeric + + + floor ( double precision ) + double precision + + + Nearest integer less than or equal to argument + + + floor(42.8) + 42 + + + floor(-42.8) + -43 + + + + + + + gamma + + gamma ( double precision ) + double precision + + + Gamma function + + + gamma(0.5) + 1.772453850905516 + + + gamma(6) + 120 + + + + + + + gcd + + gcd ( numeric_type, numeric_type ) + numeric_type + + + Greatest common divisor (the largest positive number that divides both + inputs with no remainder); returns 0 if both inputs + are zero; available for integer, bigint, + and numeric + + + gcd(1071, 462) + 21 + + + + + + + lcm + + lcm ( numeric_type, numeric_type ) + numeric_type + + + Least common multiple (the smallest strictly positive number that is + an integral multiple of both inputs); returns 0 if + either input is zero; available for integer, + bigint, and numeric + + + lcm(1071, 462) + 23562 + + + + + + + lgamma + + lgamma ( double precision ) + double precision + + + Natural logarithm of the absolute value of the gamma function + + + lgamma(1000) + 5905.220423209181 + + + + + + + ln + + ln ( numeric ) + numeric + + + ln ( double precision ) + double precision + + + Natural logarithm + + + ln(2.0) + 0.6931471805599453 + + + + + + + log + + log ( numeric ) + numeric + + + log ( double precision ) + double precision + + + Base 10 logarithm + + + log(100) + 2 + + + + + + + log10 + + log10 ( numeric ) + numeric + + + log10 ( double precision ) + double precision + + + Base 10 logarithm (same as log) + + + log10(1000) + 3 + + + + + + log ( b numeric, + x numeric ) + numeric + + + Logarithm of x to base b + + + log(2.0, 64.0) + 6.0000000000000000 + + + + + + + min_scale + + min_scale ( numeric ) + integer + + + Minimum scale (number of fractional decimal digits) needed + to represent the supplied value precisely + + + min_scale(8.4100) + 2 + + + + + + + mod + + mod ( y numeric_type, + x numeric_type ) + numeric_type + + + Remainder of y/x; + available for smallint, integer, + bigint, and numeric + + + mod(9, 4) + 1 + + + + + + + pi + + pi ( ) + double precision + + + Approximate value of π + + + pi() + 3.141592653589793 + + + + + + + power + + power ( a numeric, + b numeric ) + numeric + + + power ( a double precision, + b double precision ) + double precision + + + a raised to the power of b + + + power(9, 3) + 729 + + + + + + + radians + + radians ( double precision ) + double precision + + + Converts degrees to radians + + + radians(45.0) + 0.7853981633974483 + + + + + + + round + + round ( numeric ) + numeric + + + round ( double precision ) + double precision + + + Rounds to nearest integer. For numeric, ties are + broken by rounding away from zero. For double precision, + the tie-breaking behavior is platform dependent, but + round to nearest even is the most common rule. + + + round(42.4) + 42 + + + + + + round ( v numeric, s integer ) + numeric + + + Rounds v to s decimal + places. Ties are broken by rounding away from zero. + + + round(42.4382, 2) + 42.44 + + + round(1234.56, -1) + 1230 + + + + + + + scale + + scale ( numeric ) + integer + + + Scale of the argument (the number of decimal digits in the fractional part) + + + scale(8.4100) + 4 + + + + + + + sign + + sign ( numeric ) + numeric + + + sign ( double precision ) + double precision + + + Sign of the argument (-1, 0, or +1) + + + sign(-8.4) + -1 + + + + + + + sqrt + + sqrt ( numeric ) + numeric + + + sqrt ( double precision ) + double precision + + + Square root + + + sqrt(2) + 1.4142135623730951 + + + + + + + trim_scale + + trim_scale ( numeric ) + numeric + + + Reduces the value's scale (number of fractional decimal digits) by + removing trailing zeroes + + + trim_scale(8.4100) + 8.41 + + + + + + + trunc + + trunc ( numeric ) + numeric + + + trunc ( double precision ) + double precision + + + Truncates to integer (towards zero) + + + trunc(42.8) + 42 + + + trunc(-42.8) + -42 + + + + + + trunc ( v numeric, s integer ) + numeric + + + Truncates v to s + decimal places + + + trunc(42.4382, 2) + 42.43 + + + + + + + width_bucket + + width_bucket ( operand numeric, low numeric, high numeric, count integer ) + integer + + + width_bucket ( operand double precision, low double precision, high double precision, count integer ) + integer + + + Returns the number of the bucket in + which operand falls in a histogram + having count equal-width buckets spanning the + range low to high. + The buckets have inclusive lower bounds and exclusive upper bounds. + Returns 0 for an input less + than low, + or count+1 for an input + greater than or equal to high. + If low > high, + the behavior is mirror-reversed, with bucket 1 + now being the one just below low, and the + inclusive bounds now being on the upper side. + + + width_bucket(5.35, 0.024, 10.06, 5) + 3 + + + width_bucket(9, 10, 0, 10) + 2 + + + + + + width_bucket ( operand anycompatible, thresholds anycompatiblearray ) + integer + + + Returns the number of the bucket in + which operand falls given an array listing the + inclusive lower bounds of the buckets. + Returns 0 for an input less than the first lower + bound. operand and the array elements can be + of any type having standard comparison operators. + The thresholds array must be + sorted, smallest first, or unexpected results will be + obtained. + + + width_bucket(now(), array['yesterday', 'today', 'tomorrow']::timestamptz[]) + 2 + + + + +

+ + + shows functions for + generating random numbers. + + + + Random Functions + + + + + + Function + + + Description + + + Example(s) + + + + + + + + + random + + random ( ) + double precision + + + Returns a random value in the range 0.0 <= x < 1.0 + + + random() + 0.897124072839091 + + + + + + + random + + random ( min integer, max integer ) + integer + + + random ( min bigint, max bigint ) + bigint + + + random ( min numeric, max numeric ) + numeric + + + Returns a random value in the range + min <= x <= max. + For type numeric, the result will have the same number of + fractional decimal digits as min or + max, whichever has more. + + + random(1, 10) + 7 + + + random(-0.499, 0.499) + 0.347 + + + + + + + random_normal + + + random_normal ( + mean double precision + , stddev double precision ) + double precision + + + Returns a random value from the normal distribution with the given + parameters; mean defaults to 0.0 + and stddev defaults to 1.0 + + + random_normal(0.0, 1.0) + 0.051285419 + + + + + + + setseed + + setseed ( double precision ) + void + + + Sets the seed for subsequent random() and + random_normal() calls; + argument must be between -1.0 and 1.0, inclusive + + + setseed(0.12345) + + + + +

+ + + The random() and random_normal() + functions listed in use a + deterministic pseudo-random number generator. + It is fast but not suitable for cryptographic + applications; see the module for a more + secure alternative. + If setseed() is called, the series of results of + subsequent calls to these functions in the current session + can be repeated by re-issuing setseed() with the same + argument. + Without any prior setseed() call in the same + session, the first call to any of these functions obtains a seed + from a platform-dependent source of random bits. + + + + shows the + available trigonometric functions. Each of these functions comes in + two variants, one that measures angles in radians and one that + measures angles in degrees. + + + + Trigonometric Functions + + + + + + Function + + + Description + + + Example(s) + + + + + + + + + acos + + acos ( double precision ) + double precision + + + Inverse cosine, result in radians + + + acos(1) + 0 + + + + + + + acosd + + acosd ( double precision ) + double precision + + + Inverse cosine, result in degrees + + + acosd(0.5) + 60 + + + + + + + asin + + asin ( double precision ) + double precision + + + Inverse sine, result in radians + + + asin(1) + 1.5707963267948966 + + + + + + + asind + + asind ( double precision ) + double precision + + + Inverse sine, result in degrees + + + asind(0.5) + 30 + + + + + + + atan + + atan ( double precision ) + double precision + + + Inverse tangent, result in radians + + + atan(1) + 0.7853981633974483 + + + + + + + atand + + atand ( double precision ) + double precision + + + Inverse tangent, result in degrees + + + atand(1) + 45 + + + + + + + atan2 + + atan2 ( y double precision, + x double precision ) + double precision + + + Inverse tangent of + y/x, + result in radians + + + atan2(1, 0) + 1.5707963267948966 + + + + + + + atan2d + + atan2d ( y double precision, + x double precision ) + double precision + + + Inverse tangent of + y/x, + result in degrees + + + atan2d(1, 0) + 90 + + + + + + + cos + + cos ( double precision ) + double precision + + + Cosine, argument in radians + + + cos(0) + 1 + + + + + + + cosd + + cosd ( double precision ) + double precision + + + Cosine, argument in degrees + + + cosd(60) + 0.5 + + + + + + + cot + + cot ( double precision ) + double precision + + + Cotangent, argument in radians + + + cot(0.5) + 1.830487721712452 + + + + + + + cotd + + cotd ( double precision ) + double precision + + + Cotangent, argument in degrees + + + cotd(45) + 1 + + + + + + + sin + + sin ( double precision ) + double precision + + + Sine, argument in radians + + + sin(1) + 0.8414709848078965 + + + + + + + sind + + sind ( double precision ) + double precision + + + Sine, argument in degrees + + + sind(30) + 0.5 + + + + + + + tan + + tan ( double precision ) + double precision + + + Tangent, argument in radians + + + tan(1) + 1.5574077246549023 + + + + + + + tand + + tand ( double precision ) + double precision + + + Tangent, argument in degrees + + + tand(45) + 1 + + + + +

+ + + + Another way to work with angles measured in degrees is to use the unit + transformation functions radians() + and degrees() shown earlier. + However, using the degree-based trigonometric functions is preferred, + as that way avoids round-off error for special cases such + as sind(30). + + + + + shows the + available hyperbolic functions. + + + + Hyperbolic Functions + + + + + + Function + + + Description + + + Example(s) + + + + + + + + + sinh + + sinh ( double precision ) + double precision + + + Hyperbolic sine + + + sinh(1) + 1.1752011936438014 + + + + + + + cosh + + cosh ( double precision ) + double precision + + + Hyperbolic cosine + + + cosh(0) + 1 + + + + + + + tanh + + tanh ( double precision ) + double precision + + + Hyperbolic tangent + + + tanh(1) + 0.7615941559557649 + + + + + + + asinh + + asinh ( double precision ) + double precision + + + Inverse hyperbolic sine + + + asinh(1) + 0.881373587019543 + + + + + + + acosh + + acosh ( double precision ) + double precision + + + Inverse hyperbolic cosine + + + acosh(1) + 0 + + + + + + + atanh + + atanh ( double precision ) + double precision + + + Inverse hyperbolic tangent + + + atanh(0.5) + 0.5493061443340548 + + + + +

+ + diff --git a/doc/src/sgml/func/func-merge-support.sgml b/doc/src/sgml/func/func-merge-support.sgml new file mode 100644 index 00000000000..7f084271c13 --- /dev/null +++ b/doc/src/sgml/func/func-merge-support.sgml @@ -0,0 +1,78 @@ + + Merge Support Functions + + + MERGE + RETURNING + + + + PostgreSQL includes one merge support function + that may be used in the RETURNING list of a + command to identify the action taken for each + row; see . + + + + Merge Support Functions + + + + + + Function + + + Description + + + + + + + + + merge_action + + merge_action ( ) + text + + + Returns the merge action command executed for the current row. This + will be 'INSERT', 'UPDATE', or + 'DELETE'. + + + + +

+ + + Example: + 0 THEN + UPDATE SET in_stock = true, quantity = s.quantity + WHEN MATCHED THEN + UPDATE SET in_stock = false, quantity = 0 + WHEN NOT MATCHED THEN + INSERT (product_id, in_stock, quantity) + VALUES (s.product_id, true, s.quantity) + RETURNING merge_action(), p.*; + + merge_action | product_id | in_stock | quantity +--------------+------------+----------+---------- + UPDATE | 1001 | t | 50 + UPDATE | 1002 | f | 0 + INSERT | 1003 | t | 10 +]]> + + + + Note that this function can only be used in the RETURNING + list of a MERGE command. It is an error to use it in any + other part of a query. + + + diff --git a/doc/src/sgml/func/func-net.sgml b/doc/src/sgml/func/func-net.sgml new file mode 100644 index 00000000000..1361a44c197 --- /dev/null +++ b/doc/src/sgml/func/func-net.sgml @@ -0,0 +1,592 @@ + + Network Address Functions and Operators + + + The IP network address types, cidr and inet, + support the usual comparison operators shown in + + as well as the specialized operators and functions shown in + and + . + + + + Any cidr value can be cast to inet implicitly; + therefore, the operators and functions shown below as operating on + inet also work on cidr values. (Where there are + separate functions for inet and cidr, it is + because the behavior should be different for the two cases.) + Also, it is permitted to cast an inet value + to cidr. When this is done, any bits to the right of the + netmask are silently zeroed to create a valid cidr value. + + + + IP Address Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + inet << inet + boolean + + + Is subnet strictly contained by subnet? + This operator, and the next four, test for subnet inclusion. They + consider only the network parts of the two addresses (ignoring any + bits to the right of the netmasks) and determine whether one network + is identical to or a subnet of the other. + + + inet '192.168.1.5' << inet '192.168.1/24' + t + + + inet '192.168.0.5' << inet '192.168.1/24' + f + + + inet '192.168.1/24' << inet '192.168.1/24' + f + + + + + + inet <<= inet + boolean + + + Is subnet contained by or equal to subnet? + + + inet '192.168.1/24' <<= inet '192.168.1/24' + t + + + + + + inet >> inet + boolean + + + Does subnet strictly contain subnet? + + + inet '192.168.1/24' >> inet '192.168.1.5' + t + + + + + + inet >>= inet + boolean + + + Does subnet contain or equal subnet? + + + inet '192.168.1/24' >>= inet '192.168.1/24' + t + + + + + + inet && inet + boolean + + + Does either subnet contain or equal the other? + + + inet '192.168.1/24' && inet '192.168.1.80/28' + t + + + inet '192.168.1/24' && inet '192.168.2.0/28' + f + + + + + + ~ inet + inet + + + Computes bitwise NOT. + + + ~ inet '192.168.1.6' + 63.87.254.249 + + + + + + inet & inet + inet + + + Computes bitwise AND. + + + inet '192.168.1.6' & inet '0.0.0.255' + 0.0.0.6 + + + + + + inet | inet + inet + + + Computes bitwise OR. + + + inet '192.168.1.6' | inet '0.0.0.255' + 192.168.1.255 + + + + + + inet + bigint + inet + + + Adds an offset to an address. + + + inet '192.168.1.6' + 25 + 192.168.1.31 + + + + + + bigint + inet + inet + + + Adds an offset to an address. + + + 200 + inet '::ffff:fff0:1' + ::ffff:255.240.0.201 + + + + + + inet - bigint + inet + + + Subtracts an offset from an address. + + + inet '192.168.1.43' - 36 + 192.168.1.7 + + + + + + inet - inet + bigint + + + Computes the difference of two addresses. + + + inet '192.168.1.43' - inet '192.168.1.19' + 24 + + + inet '::1' - inet '::ffff:1' + -4294901760 + + + + +

+ + + IP Address Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + abbrev + + abbrev ( inet ) + text + + + Creates an abbreviated display format as text. + (The result is the same as the inet output function + produces; it is abbreviated only in comparison to the + result of an explicit cast to text, which for historical + reasons will never suppress the netmask part.) + + + abbrev(inet '10.1.0.0/32') + 10.1.0.0 + + + + + + abbrev ( cidr ) + text + + + Creates an abbreviated display format as text. + (The abbreviation consists of dropping all-zero octets to the right + of the netmask; more examples are in + .) + + + abbrev(cidr '10.1.0.0/16') + 10.1/16 + + + + + + + broadcast + + broadcast ( inet ) + inet + + + Computes the broadcast address for the address's network. + + + broadcast(inet '192.168.1.5/24') + 192.168.1.255/24 + + + + + + + family + + family ( inet ) + integer + + + Returns the address's family: 4 for IPv4, + 6 for IPv6. + + + family(inet '::1') + 6 + + + + + + + host + + host ( inet ) + text + + + Returns the IP address as text, ignoring the netmask. + + + host(inet '192.168.1.0/24') + 192.168.1.0 + + + + + + + hostmask + + hostmask ( inet ) + inet + + + Computes the host mask for the address's network. + + + hostmask(inet '192.168.23.20/30') + 0.0.0.3 + + + + + + + inet_merge + + inet_merge ( inet, inet ) + cidr + + + Computes the smallest network that includes both of the given networks. + + + inet_merge(inet '192.168.1.5/24', inet '192.168.2.5/24') + 192.168.0.0/22 + + + + + + + inet_same_family + + inet_same_family ( inet, inet ) + boolean + + + Tests whether the addresses belong to the same IP family. + + + inet_same_family(inet '192.168.1.5/24', inet '::1') + f + + + + + + + masklen + + masklen ( inet ) + integer + + + Returns the netmask length in bits. + + + masklen(inet '192.168.1.5/24') + 24 + + + + + + + netmask + + netmask ( inet ) + inet + + + Computes the network mask for the address's network. + + + netmask(inet '192.168.1.5/24') + 255.255.255.0 + + + + + + + network + + network ( inet ) + cidr + + + Returns the network part of the address, zeroing out + whatever is to the right of the netmask. + (This is equivalent to casting the value to cidr.) + + + network(inet '192.168.1.5/24') + 192.168.1.0/24 + + + + + + + set_masklen + + set_masklen ( inet, integer ) + inet + + + Sets the netmask length for an inet value. + The address part does not change. + + + set_masklen(inet '192.168.1.5/24', 16) + 192.168.1.5/16 + + + + + + set_masklen ( cidr, integer ) + cidr + + + Sets the netmask length for a cidr value. + Address bits to the right of the new netmask are set to zero. + + + set_masklen(cidr '192.168.1.0/24', 16) + 192.168.0.0/16 + + + + + + + text + + text ( inet ) + text + + + Returns the unabbreviated IP address and netmask length as text. + (This has the same result as an explicit cast to text.) + + + text(inet '192.168.1.5') + 192.168.1.5/32 + + + + +

+ + + + The abbrev, host, + and text functions are primarily intended to offer + alternative display formats for IP addresses. + + + + + The MAC address types, macaddr and macaddr8, + support the usual comparison operators shown in + + as well as the specialized functions shown in + . + In addition, they support the bitwise logical operators + ~, & and | + (NOT, AND and OR), just as shown above for IP addresses. + + + + MAC Address Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + trunc + + trunc ( macaddr ) + macaddr + + + Sets the last 3 bytes of the address to zero. The remaining prefix + can be associated with a particular manufacturer (using data not + included in PostgreSQL). + + + trunc(macaddr '12:34:56:78:90:ab') + 12:34:56:00:00:00 + + + + + + trunc ( macaddr8 ) + macaddr8 + + + Sets the last 5 bytes of the address to zero. The remaining prefix + can be associated with a particular manufacturer (using data not + included in PostgreSQL). + + + trunc(macaddr8 '12:34:56:78:90:ab:cd:ef') + 12:34:56:00:00:00:00:00 + + + + + + + macaddr8_set7bit + + macaddr8_set7bit ( macaddr8 ) + macaddr8 + + + Sets the 7th bit of the address to one, creating what is known as + modified EUI-64, for inclusion in an IPv6 address. + + + macaddr8_set7bit(macaddr8 '00:34:56:ab:cd:ef') + 02:34:56:ff:fe:ab:cd:ef + + + + +

+ + diff --git a/doc/src/sgml/func/func-range.sgml b/doc/src/sgml/func/func-range.sgml new file mode 100644 index 00000000000..2dc40348a57 --- /dev/null +++ b/doc/src/sgml/func/func-range.sgml @@ -0,0 +1,1053 @@ + + Range/Multirange Functions and Operators + + + See for an overview of range types. + + + + shows the specialized operators + available for range types. + shows the specialized operators + available for multirange types. + In addition to those, the usual comparison operators shown in + are available for range + and multirange types. The comparison operators order first by the range lower + bounds, and only if those are equal do they compare the upper bounds. The + multirange operators compare each range until one is unequal. This + does not usually result in a useful overall ordering, but the operators are + provided to allow unique indexes to be constructed on ranges. + + + + Range Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + anyrange @> anyrange + boolean + + + Does the first range contain the second? + + + int4range(2,4) @> int4range(2,3) + t + + + + + + anyrange @> anyelement + boolean + + + Does the range contain the element? + + + '[2011-01-01,2011-03-01)'::tsrange @> '2011-01-10'::timestamp + t + + + + + + anyrange <@ anyrange + boolean + + + Is the first range contained by the second? + + + int4range(2,4) <@ int4range(1,7) + t + + + + + + anyelement <@ anyrange + boolean + + + Is the element contained in the range? + + + 42 <@ int4range(1,7) + f + + + + + + anyrange && anyrange + boolean + + + Do the ranges overlap, that is, have any elements in common? + + + int8range(3,7) && int8range(4,12) + t + + + + + + anyrange << anyrange + boolean + + + Is the first range strictly left of the second? + + + int8range(1,10) << int8range(100,110) + t + + + + + + anyrange >> anyrange + boolean + + + Is the first range strictly right of the second? + + + int8range(50,60) >> int8range(20,30) + t + + + + + + anyrange &< anyrange + boolean + + + Does the first range not extend to the right of the second? + + + int8range(1,20) &< int8range(18,20) + t + + + + + + anyrange &> anyrange + boolean + + + Does the first range not extend to the left of the second? + + + int8range(7,20) &> int8range(5,10) + t + + + + + + anyrange -|- anyrange + boolean + + + Are the ranges adjacent? + + + numrange(1.1,2.2) -|- numrange(2.2,3.3) + t + + + + + + anyrange + anyrange + anyrange + + + Computes the union of the ranges. The ranges must overlap or be + adjacent, so that the union is a single range (but + see range_merge()). + + + numrange(5,15) + numrange(10,20) + [5,20) + + + + + + anyrange * anyrange + anyrange + + + Computes the intersection of the ranges. + + + int8range(5,15) * int8range(10,20) + [10,15) + + + + + + anyrange - anyrange + anyrange + + + Computes the difference of the ranges. The second range must not be + contained in the first in such a way that the difference would not be + a single range. + + + int8range(5,15) - int8range(10,20) + [5,10) + + + + +

+ + + Multirange Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + anymultirange @> anymultirange + boolean + + + Does the first multirange contain the second? + + + '{[2,4)}'::int4multirange @> '{[2,3)}'::int4multirange + t + + + + + + anymultirange @> anyrange + boolean + + + Does the multirange contain the range? + + + '{[2,4)}'::int4multirange @> int4range(2,3) + t + + + + + + anymultirange @> anyelement + boolean + + + Does the multirange contain the element? + + + '{[2011-01-01,2011-03-01)}'::tsmultirange @> '2011-01-10'::timestamp + t + + + + + + anyrange @> anymultirange + boolean + + + Does the range contain the multirange? + + + '[2,4)'::int4range @> '{[2,3)}'::int4multirange + t + + + + + + anymultirange <@ anymultirange + boolean + + + Is the first multirange contained by the second? + + + '{[2,4)}'::int4multirange <@ '{[1,7)}'::int4multirange + t + + + + + + anymultirange <@ anyrange + boolean + + + Is the multirange contained by the range? + + + '{[2,4)}'::int4multirange <@ int4range(1,7) + t + + + + + + anyrange <@ anymultirange + boolean + + + Is the range contained by the multirange? + + + int4range(2,4) <@ '{[1,7)}'::int4multirange + t + + + + + + anyelement <@ anymultirange + boolean + + + Is the element contained by the multirange? + + + 4 <@ '{[1,7)}'::int4multirange + t + + + + + + anymultirange && anymultirange + boolean + + + Do the multiranges overlap, that is, have any elements in common? + + + '{[3,7)}'::int8multirange && '{[4,12)}'::int8multirange + t + + + + + + anymultirange && anyrange + boolean + + + Does the multirange overlap the range? + + + '{[3,7)}'::int8multirange && int8range(4,12) + t + + + + + + anyrange && anymultirange + boolean + + + Does the range overlap the multirange? + + + int8range(3,7) && '{[4,12)}'::int8multirange + t + + + + + + anymultirange << anymultirange + boolean + + + Is the first multirange strictly left of the second? + + + '{[1,10)}'::int8multirange << '{[100,110)}'::int8multirange + t + + + + + + anymultirange << anyrange + boolean + + + Is the multirange strictly left of the range? + + + '{[1,10)}'::int8multirange << int8range(100,110) + t + + + + + + anyrange << anymultirange + boolean + + + Is the range strictly left of the multirange? + + + int8range(1,10) << '{[100,110)}'::int8multirange + t + + + + + + anymultirange >> anymultirange + boolean + + + Is the first multirange strictly right of the second? + + + '{[50,60)}'::int8multirange >> '{[20,30)}'::int8multirange + t + + + + + + anymultirange >> anyrange + boolean + + + Is the multirange strictly right of the range? + + + '{[50,60)}'::int8multirange >> int8range(20,30) + t + + + + + + anyrange >> anymultirange + boolean + + + Is the range strictly right of the multirange? + + + int8range(50,60) >> '{[20,30)}'::int8multirange + t + + + + + + anymultirange &< anymultirange + boolean + + + Does the first multirange not extend to the right of the second? + + + '{[1,20)}'::int8multirange &< '{[18,20)}'::int8multirange + t + + + + + + anymultirange &< anyrange + boolean + + + Does the multirange not extend to the right of the range? + + + '{[1,20)}'::int8multirange &< int8range(18,20) + t + + + + + + anyrange &< anymultirange + boolean + + + Does the range not extend to the right of the multirange? + + + int8range(1,20) &< '{[18,20)}'::int8multirange + t + + + + + + anymultirange &> anymultirange + boolean + + + Does the first multirange not extend to the left of the second? + + + '{[7,20)}'::int8multirange &> '{[5,10)}'::int8multirange + t + + + + + + anymultirange &> anyrange + boolean + + + Does the multirange not extend to the left of the range? + + + '{[7,20)}'::int8multirange &> int8range(5,10) + t + + + + + + anyrange &> anymultirange + boolean + + + Does the range not extend to the left of the multirange? + + + int8range(7,20) &> '{[5,10)}'::int8multirange + t + + + + + + anymultirange -|- anymultirange + boolean + + + Are the multiranges adjacent? + + + '{[1.1,2.2)}'::nummultirange -|- '{[2.2,3.3)}'::nummultirange + t + + + + + + anymultirange -|- anyrange + boolean + + + Is the multirange adjacent to the range? + + + '{[1.1,2.2)}'::nummultirange -|- numrange(2.2,3.3) + t + + + + + + anyrange -|- anymultirange + boolean + + + Is the range adjacent to the multirange? + + + numrange(1.1,2.2) -|- '{[2.2,3.3)}'::nummultirange + t + + + + + + anymultirange + anymultirange + anymultirange + + + Computes the union of the multiranges. The multiranges need not overlap + or be adjacent. + + + '{[5,10)}'::nummultirange + '{[15,20)}'::nummultirange + {[5,10), [15,20)} + + + + + + anymultirange * anymultirange + anymultirange + + + Computes the intersection of the multiranges. + + + '{[5,15)}'::int8multirange * '{[10,20)}'::int8multirange + {[10,15)} + + + + + + anymultirange - anymultirange + anymultirange + + + Computes the difference of the multiranges. + + + '{[5,20)}'::int8multirange - '{[10,15)}'::int8multirange + {[5,10), [15,20)} + + + + +

+ + + The left-of/right-of/adjacent operators always return false when an empty + range or multirange is involved; that is, an empty range is not considered to + be either before or after any other range. + + + + Elsewhere empty ranges and multiranges are treated as the additive identity: + anything unioned with an empty value is itself. Anything minus an empty + value is itself. An empty multirange has exactly the same points as an empty + range. Every range contains the empty range. Every multirange contains as many + empty ranges as you like. + + + + The range union and difference operators will fail if the resulting range would + need to contain two disjoint sub-ranges, as such a range cannot be + represented. There are separate operators for union and difference that take + multirange parameters and return a multirange, and they do not fail even if + their arguments are disjoint. So if you need a union or difference operation + for ranges that may be disjoint, you can avoid errors by first casting your + ranges to multiranges. + + + + shows the functions + available for use with range types. + shows the functions + available for use with multirange types. + + + + Range Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + lower + + lower ( anyrange ) + anyelement + + + Extracts the lower bound of the range (NULL if the + range is empty or has no lower bound). + + + lower(numrange(1.1,2.2)) + 1.1 + + + + + + + upper + + upper ( anyrange ) + anyelement + + + Extracts the upper bound of the range (NULL if the + range is empty or has no upper bound). + + + upper(numrange(1.1,2.2)) + 2.2 + + + + + + + isempty + + isempty ( anyrange ) + boolean + + + Is the range empty? + + + isempty(numrange(1.1,2.2)) + f + + + + + + + lower_inc + + lower_inc ( anyrange ) + boolean + + + Is the range's lower bound inclusive? + + + lower_inc(numrange(1.1,2.2)) + t + + + + + + + upper_inc + + upper_inc ( anyrange ) + boolean + + + Is the range's upper bound inclusive? + + + upper_inc(numrange(1.1,2.2)) + f + + + + + + + lower_inf + + lower_inf ( anyrange ) + boolean + + + Does the range have no lower bound? (A lower bound of + -Infinity returns false.) + + + lower_inf('(,)'::daterange) + t + + + + + + + upper_inf + + upper_inf ( anyrange ) + boolean + + + Does the range have no upper bound? (An upper bound of + Infinity returns false.) + + + upper_inf('(,)'::daterange) + t + + + + + + + range_merge + + range_merge ( anyrange, anyrange ) + anyrange + + + Computes the smallest range that includes both of the given ranges. + + + range_merge('[1,2)'::int4range, '[3,4)'::int4range) + [1,4) + + + + +

+ + + Multirange Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + lower + + lower ( anymultirange ) + anyelement + + + Extracts the lower bound of the multirange (NULL if the + multirange is empty or has no lower bound). + + + lower('{[1.1,2.2)}'::nummultirange) + 1.1 + + + + + + + upper + + upper ( anymultirange ) + anyelement + + + Extracts the upper bound of the multirange (NULL if the + multirange is empty or has no upper bound). + + + upper('{[1.1,2.2)}'::nummultirange) + 2.2 + + + + + + + isempty + + isempty ( anymultirange ) + boolean + + + Is the multirange empty? + + + isempty('{[1.1,2.2)}'::nummultirange) + f + + + + + + + lower_inc + + lower_inc ( anymultirange ) + boolean + + + Is the multirange's lower bound inclusive? + + + lower_inc('{[1.1,2.2)}'::nummultirange) + t + + + + + + + upper_inc + + upper_inc ( anymultirange ) + boolean + + + Is the multirange's upper bound inclusive? + + + upper_inc('{[1.1,2.2)}'::nummultirange) + f + + + + + + + lower_inf + + lower_inf ( anymultirange ) + boolean + + + Does the multirange have no lower bound? (A lower bound of + -Infinity returns false.) + + + lower_inf('{(,)}'::datemultirange) + t + + + + + + + upper_inf + + upper_inf ( anymultirange ) + boolean + + + Does the multirange have no upper bound? (An upper bound of + Infinity returns false.) + + + upper_inf('{(,)}'::datemultirange) + t + + + + + + + range_merge + + range_merge ( anymultirange ) + anyrange + + + Computes the smallest range that includes the entire multirange. + + + range_merge('{[1,2), [3,4)}'::int4multirange) + [1,4) + + + + + + + multirange (function) + + multirange ( anyrange ) + anymultirange + + + Returns a multirange containing just the given range. + + + multirange('[1,2)'::int4range) + {[1,2)} + + + + + + + unnest + for multirange + + unnest ( anymultirange ) + setof anyrange + + + Expands a multirange into a set of ranges in ascending order. + + + unnest('{[1,2), [3,4)}'::int4multirange) + + + [1,2) + [3,4) + + + + + +

+ + + The lower_inc, upper_inc, + lower_inf, and upper_inf + functions all return false for an empty range or multirange. + + diff --git a/doc/src/sgml/func/func-sequence.sgml b/doc/src/sgml/func/func-sequence.sgml new file mode 100644 index 00000000000..e9f5b4e8e6b --- /dev/null +++ b/doc/src/sgml/func/func-sequence.sgml @@ -0,0 +1,195 @@ + + Sequence Manipulation Functions + + + sequence + + + + This section describes functions for operating on sequence + objects, also called sequence generators or just sequences. + Sequence objects are special single-row tables created with . + Sequence objects are commonly used to generate unique identifiers + for rows of a table. The sequence functions, listed in , provide simple, multiuser-safe + methods for obtaining successive sequence values from sequence + objects. + + + + Sequence Functions + + + + + Function + + + Description + + + + + + + + + nextval + + nextval ( regclass ) + bigint + + + Advances the sequence object to its next value and returns that value. + This is done atomically: even if multiple sessions + execute nextval concurrently, each will safely + receive a distinct sequence value. + If the sequence object has been created with default parameters, + successive nextval calls will return successive + values beginning with 1. Other behaviors can be obtained by using + appropriate parameters in the + command. + + + This function requires USAGE + or UPDATE privilege on the sequence. + + + + + + + setval + + setval ( regclass, bigint , boolean ) + bigint + + + Sets the sequence object's current value, and optionally + its is_called flag. The two-parameter + form sets the sequence's last_value field to the + specified value and sets its is_called field to + true, meaning that the next + nextval will advance the sequence before + returning a value. The value that will be reported + by currval is also set to the specified value. + In the three-parameter form, is_called can be set + to either true + or false. true has the same + effect as the two-parameter form. If it is set + to false, the next nextval + will return exactly the specified value, and sequence advancement + commences with the following nextval. + Furthermore, the value reported by currval is not + changed in this case. For example, + +SELECT setval('myseq', 42); Next nextval will return 43 +SELECT setval('myseq', 42, true); Same as above +SELECT setval('myseq', 42, false); Next nextval will return 42 + + The result returned by setval is just the value of its + second argument. + + + This function requires UPDATE privilege on the + sequence. + + + + + + + currval + + currval ( regclass ) + bigint + + + Returns the value most recently obtained + by nextval for this sequence in the current + session. (An error is reported if nextval has + never been called for this sequence in this session.) Because this is + returning a session-local value, it gives a predictable answer whether + or not other sessions have executed nextval since + the current session did. + + + This function requires USAGE + or SELECT privilege on the sequence. + + + + + + + lastval + + lastval () + bigint + + + Returns the value most recently returned by + nextval in the current session. This function is + identical to currval, except that instead + of taking the sequence name as an argument it refers to whichever + sequence nextval was most recently applied to + in the current session. It is an error to call + lastval if nextval + has not yet been called in the current session. + + + This function requires USAGE + or SELECT privilege on the last used sequence. + + + + +

+ + + + To avoid blocking concurrent transactions that obtain numbers from + the same sequence, the value obtained by nextval + is not reclaimed for re-use if the calling transaction later aborts. + This means that transaction aborts or database crashes can result in + gaps in the sequence of assigned values. That can happen without a + transaction abort, too. For example an INSERT with + an ON CONFLICT clause will compute the to-be-inserted + tuple, including doing any required nextval + calls, before detecting any conflict that would cause it to follow + the ON CONFLICT rule instead. + Thus, PostgreSQL sequence + objects cannot be used to obtain gapless + sequences. + + + + Likewise, sequence state changes made by setval + are immediately visible to other transactions, and are not undone if + the calling transaction rolls back. + + + + If the database cluster crashes before committing a transaction + containing a nextval + or setval call, the sequence state change might + not have made its way to persistent storage, so that it is uncertain + whether the sequence will have its original or updated state after the + cluster restarts. This is harmless for usage of the sequence within + the database, since other effects of uncommitted transactions will not + be visible either. However, if you wish to use a sequence value for + persistent outside-the-database purposes, make sure that the + nextval call has been committed before doing so. + + + + + The sequence to be operated on by a sequence function is specified by + a regclass argument, which is simply the OID of the sequence in the + pg_class system catalog. You do not have to look up the + OID by hand, however, since the regclass data type's input + converter will do the work for you. See + for details. + + diff --git a/doc/src/sgml/func/func-srf.sgml b/doc/src/sgml/func/func-srf.sgml new file mode 100644 index 00000000000..eafc961c9f9 --- /dev/null +++ b/doc/src/sgml/func/func-srf.sgml @@ -0,0 +1,306 @@ + + Set Returning Functions + + + set returning functions + functions + + + + This section describes functions that possibly return more than one row. + The most widely used functions in this class are series generating + functions, as detailed in and + . Other, more specialized + set-returning functions are described elsewhere in this manual. + See for ways to combine multiple + set-returning functions. + + + + Series Generating Functions + + + + + Function + + + Description + + + + + + + + + generate_series + + generate_series ( start integer, stop integer , step integer ) + setof integer + + + generate_series ( start bigint, stop bigint , step bigint ) + setof bigint + + + generate_series ( start numeric, stop numeric , step numeric ) + setof numeric + + + Generates a series of values from start + to stop, with a step size + of step. step + defaults to 1. + + + + + + generate_series ( start timestamp, stop timestamp, step interval ) + setof timestamp + + + generate_series ( start timestamp with time zone, stop timestamp with time zone, step interval , timezone text ) + setof timestamp with time zone + + + Generates a series of values from start + to stop, with a step size + of step. + In the timezone-aware form, times of day and daylight-savings + adjustments are computed according to the time zone named by + the timezone argument, or the current + setting if that is omitted. + + + + +

+ + + When step is positive, zero rows are returned if + start is greater than stop. + Conversely, when step is negative, zero rows are + returned if start is less than stop. + Zero rows are also returned if any input is NULL. + It is an error + for step to be zero. Some examples follow: + +SELECT * FROM generate_series(2,4); + generate_series +----------------- + 2 + 3 + 4 +(3 rows) + +SELECT * FROM generate_series(5,1,-2); + generate_series +----------------- + 5 + 3 + 1 +(3 rows) + +SELECT * FROM generate_series(4,3); + generate_series +----------------- +(0 rows) + +SELECT generate_series(1.1, 4, 1.3); + generate_series +----------------- + 1.1 + 2.4 + 3.7 +(3 rows) + +-- this example relies on the date-plus-integer operator: +SELECT current_date + s.a AS dates FROM generate_series(0,14,7) AS s(a); + dates +------------ + 2004-02-05 + 2004-02-12 + 2004-02-19 +(3 rows) + +SELECT * FROM generate_series('2008-03-01 00:00'::timestamp, + '2008-03-04 12:00', '10 hours'); + generate_series +--------------------- + 2008-03-01 00:00:00 + 2008-03-01 10:00:00 + 2008-03-01 20:00:00 + 2008-03-02 06:00:00 + 2008-03-02 16:00:00 + 2008-03-03 02:00:00 + 2008-03-03 12:00:00 + 2008-03-03 22:00:00 + 2008-03-04 08:00:00 +(9 rows) + +-- this example assumes that TimeZone is set to UTC; note the DST transition: +SELECT * FROM generate_series('2001-10-22 00:00 -04:00'::timestamptz, + '2001-11-01 00:00 -05:00'::timestamptz, + '1 day'::interval, 'America/New_York'); + generate_series +------------------------ + 2001-10-22 04:00:00+00 + 2001-10-23 04:00:00+00 + 2001-10-24 04:00:00+00 + 2001-10-25 04:00:00+00 + 2001-10-26 04:00:00+00 + 2001-10-27 04:00:00+00 + 2001-10-28 04:00:00+00 + 2001-10-29 05:00:00+00 + 2001-10-30 05:00:00+00 + 2001-10-31 05:00:00+00 + 2001-11-01 05:00:00+00 +(11 rows) + + + + + Subscript Generating Functions + + + + + Function + + + Description + + + + + + + + + generate_subscripts + + generate_subscripts ( array anyarray, dim integer ) + setof integer + + + Generates a series comprising the valid subscripts of + the dim'th dimension of the given array. + + + + + + generate_subscripts ( array anyarray, dim integer, reverse boolean ) + setof integer + + + Generates a series comprising the valid subscripts of + the dim'th dimension of the given array. + When reverse is true, returns the series in + reverse order. + + + + +

+ + + generate_subscripts is a convenience function that generates + the set of valid subscripts for the specified dimension of the given + array. + Zero rows are returned for arrays that do not have the requested dimension, + or if any input is NULL. + Some examples follow: + +-- basic usage: +SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1) AS s; + s +--- + 1 + 2 + 3 + 4 +(4 rows) + +-- presenting an array, the subscript and the subscripted +-- value requires a subquery: +SELECT * FROM arrays; + a +-------------------- + {-1,-2} + {100,200,300} +(2 rows) + +SELECT a AS array, s AS subscript, a[s] AS value +FROM (SELECT generate_subscripts(a, 1) AS s, a FROM arrays) foo; + array | subscript | value +---------------+-----------+------- + {-1,-2} | 1 | -1 + {-1,-2} | 2 | -2 + {100,200,300} | 1 | 100 + {100,200,300} | 2 | 200 + {100,200,300} | 3 | 300 +(5 rows) + +-- unnest a 2D array: +CREATE OR REPLACE FUNCTION unnest2(anyarray) +RETURNS SETOF anyelement AS $$ +select $1[i][j] + from generate_subscripts($1,1) g1(i), + generate_subscripts($1,2) g2(j); +$$ LANGUAGE sql IMMUTABLE; +CREATE FUNCTION +SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]); + unnest2 +--------- + 1 + 2 + 3 + 4 +(4 rows) + + + + + ordinality + + + + When a function in the FROM clause is suffixed + by WITH ORDINALITY, a bigint column is + appended to the function's output column(s), which starts from 1 and + increments by 1 for each row of the function's output. + This is most useful in the case of set returning + functions such as unnest(). + + +-- set returning function WITH ORDINALITY: +SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n); + ls | n +-----------------+---- + pg_serial | 1 + pg_twophase | 2 + postmaster.opts | 3 + pg_notify | 4 + postgresql.conf | 5 + pg_tblspc | 6 + logfile | 7 + base | 8 + postmaster.pid | 9 + pg_ident.conf | 10 + global | 11 + pg_xact | 12 + pg_snapshots | 13 + pg_multixact | 14 + PG_VERSION | 15 + pg_wal | 16 + pg_hba.conf | 17 + pg_stat_tmp | 18 + pg_subtrans | 19 +(19 rows) + + + + diff --git a/doc/src/sgml/func/func-statistics.sgml b/doc/src/sgml/func/func-statistics.sgml new file mode 100644 index 00000000000..22dee263cc2 --- /dev/null +++ b/doc/src/sgml/func/func-statistics.sgml @@ -0,0 +1,85 @@ + + Statistics Information Functions + + + function + statistics + + + + PostgreSQL provides a function to inspect complex + statistics defined using the CREATE STATISTICS command. + + + + Inspecting MCV Lists + + + pg_mcv_list_items + + + +pg_mcv_list_items ( pg_mcv_list ) setof record + + + + pg_mcv_list_items returns a set of records describing + all items stored in a multi-column MCV list. It + returns the following columns: + + + + + + Name + Type + Description + + + + + + index + integer + index of the item in the MCV list + + + values + text[] + values stored in the MCV item + + + nulls + boolean[] + flags identifying NULL values + + + frequency + double precision + frequency of this MCV item + + + base_frequency + double precision + base frequency of this MCV item + + + + + + + + The pg_mcv_list_items function can be used like this: + + +SELECT m.* FROM pg_statistic_ext join pg_statistic_ext_data on (oid = stxoid), + pg_mcv_list_items(stxdmcv) m WHERE stxname = 'stts'; + + + Values of the pg_mcv_list type can be obtained only from the + pg_statistic_ext_data.stxdmcv + column. + + + + diff --git a/doc/src/sgml/func/func-string.sgml b/doc/src/sgml/func/func-string.sgml new file mode 100644 index 00000000000..3eec93eb339 --- /dev/null +++ b/doc/src/sgml/func/func-string.sgml @@ -0,0 +1,1818 @@ + + String Functions and Operators + + + This section describes functions and operators for examining and + manipulating string values. Strings in this context include values + of the types character, character varying, + and text. Except where noted, these functions and operators + are declared to accept and return type text. They will + interchangeably accept character varying arguments. + Values of type character will be converted + to text before the function or operator is applied, resulting + in stripping any trailing spaces in the character value. + + + + SQL defines some string functions that use + key words, rather than commas, to separate + arguments. Details are in + . + PostgreSQL also provides versions of these functions + that use the regular function invocation syntax + (see ). + + + + + The string concatenation operator (||) will accept + non-string input, so long as at least one input is of string type, as shown + in . For other cases, inserting an + explicit coercion to text can be used to have non-string input + accepted. + + + + + <acronym>SQL</acronym> String Functions and Operators + + + + + Function/Operator + + + Description + + + Example(s) + + + + + + + + + character string + concatenation + + text || text + text + + + Concatenates the two strings. + + + 'Post' || 'greSQL' + PostgreSQL + + + + + + text || anynonarray + text + + + anynonarray || text + text + + + Converts the non-string input to text, then concatenates the two + strings. (The non-string input cannot be of an array type, because + that would create ambiguity with the array || + operators. If you want to concatenate an array's text equivalent, + cast it to text explicitly.) + + + 'Value: ' || 42 + Value: 42 + + + + + + + btrim + + btrim ( string text + , characters text ) + text + + + Removes the longest string containing only characters + in characters (a space by default) + from the start and end of string. + + + btrim('xyxtrimyyx', 'xyz') + trim + + + + + + + normalized + + + Unicode normalization + + text IS NOT form NORMALIZED + boolean + + + Checks whether the string is in the specified Unicode normalization + form. The optional form key word specifies the + form: NFC (the default), NFD, + NFKC, or NFKD. This expression can + only be used when the server encoding is UTF8. Note + that checking for normalization using this expression is often faster + than normalizing possibly already normalized strings. + + + U&'\0061\0308bc' IS NFD NORMALIZED + t + + + + + + + bit_length + + bit_length ( text ) + integer + + + Returns number of bits in the string (8 + times the octet_length). + + + bit_length('jose') + 32 + + + + + + + char_length + + + character string + length + + + length + of a character string + character string, length + + char_length ( text ) + integer + + + + character_length + + character_length ( text ) + integer + + + Returns number of characters in the string. + + + char_length('josé') + 4 + + + + + + + lower + + lower ( text ) + text + + + Converts the string to all lower case, according to the rules of the + database's locale. + + + lower('TOM') + tom + + + + + + + lpad + + lpad ( string text, + length integer + , fill text ) + text + + + Extends the string to length + length by prepending the characters + fill (a space by default). If the + string is already longer than + length then it is truncated (on the right). + + + lpad('hi', 5, 'xy') + xyxhi + + + + + + + ltrim + + ltrim ( string text + , characters text ) + text + + + Removes the longest string containing only characters in + characters (a space by default) from the start of + string. + + + ltrim('zzzytest', 'xyz') + test + + + + + + + normalize + + + Unicode normalization + + normalize ( text + , form ) + text + + + Converts the string to the specified Unicode + normalization form. The optional form key word + specifies the form: NFC (the default), + NFD, NFKC, or + NFKD. This function can only be used when the + server encoding is UTF8. + + + normalize(U&'\0061\0308bc', NFC) + U&'\00E4bc' + + + + + + + octet_length + + octet_length ( text ) + integer + + + Returns number of bytes in the string. + + + octet_length('josé') + 5 (if server encoding is UTF8) + + + + + + + octet_length + + octet_length ( character ) + integer + + + Returns number of bytes in the string. Since this version of the + function accepts type character directly, it will not + strip trailing spaces. + + + octet_length('abc '::character(4)) + 4 + + + + + + + overlay + + overlay ( string text PLACING newsubstring text FROM start integer FOR count integer ) + text + + + Replaces the substring of string that starts at + the start'th character and extends + for count characters + with newsubstring. + If count is omitted, it defaults to the length + of newsubstring. + + + overlay('Txxxxas' placing 'hom' from 2 for 4) + Thomas + + + + + + + position + + position ( substring text IN string text ) + integer + + + Returns first starting index of the specified + substring within + string, or zero if it's not present. + + + position('om' in 'Thomas') + 3 + + + + + + + rpad + + rpad ( string text, + length integer + , fill text ) + text + + + Extends the string to length + length by appending the characters + fill (a space by default). If the + string is already longer than + length then it is truncated. + + + rpad('hi', 5, 'xy') + hixyx + + + + + + + rtrim + + rtrim ( string text + , characters text ) + text + + + Removes the longest string containing only characters in + characters (a space by default) from the end of + string. + + + rtrim('testxxzx', 'xyz') + test + + + + + + + substring + + substring ( string text FROM start integer FOR count integer ) + text + + + Extracts the substring of string starting at + the start'th character if that is specified, + and stopping after count characters if that is + specified. Provide at least one of start + and count. + + + substring('Thomas' from 2 for 3) + hom + + + substring('Thomas' from 3) + omas + + + substring('Thomas' for 2) + Th + + + + + + substring ( string text FROM pattern text ) + text + + + Extracts the first substring matching POSIX regular expression; see + . + + + substring('Thomas' from '...$') + mas + + + + + + substring ( string text SIMILAR pattern text ESCAPE escape text ) + text + + + substring ( string text FROM pattern text FOR escape text ) + text + + + Extracts the first substring matching SQL regular expression; + see . The first form has + been specified since SQL:2003; the second form was only in SQL:1999 + and should be considered obsolete. + + + substring('Thomas' similar '%#"o_a#"_' escape '#') + oma + + + + + + + trim + + trim ( LEADING | TRAILING | BOTH + characters text FROM + string text ) + text + + + Removes the longest string containing only characters in + characters (a space by default) from the + start, end, or both ends (BOTH is the default) + of string. + + + trim(both 'xyz' from 'yxTomxx') + Tom + + + + + + trim ( LEADING | TRAILING | BOTH FROM + string text , + characters text ) + text + + + This is a non-standard syntax for trim(). + + + trim(both from 'yxTomxx', 'xyz') + Tom + + + + + + + unicode_assigned + + unicode_assigned ( text ) + boolean + + + Returns true if all characters in the string are + assigned Unicode codepoints; false otherwise. This + function can only be used when the server encoding is + UTF8. + + + + + + + upper + + upper ( text ) + text + + + Converts the string to all upper case, according to the rules of the + database's locale. + + + upper('tom') + TOM + + + + +

+ + + Additional string manipulation functions and operators are available + and are listed in . (Some of + these are used internally to implement + the SQL-standard string functions listed in + .) + There are also pattern-matching operators, which are described in + , and operators for full-text + search, which are described in . + + + + Other String Functions and Operators + + + + + Function/Operator + + + Description + + + Example(s) + + + + + + + + + character string + prefix test + + text ^@ text + boolean + + + Returns true if the first string starts with the second string + (equivalent to the starts_with() function). + + + 'alphabet' ^@ 'alph' + t + + + + + + + ascii + + ascii ( text ) + integer + + + Returns the numeric code of the first character of the argument. + In UTF8 encoding, returns the Unicode code point + of the character. In other multibyte encodings, the argument must + be an ASCII character. + + + ascii('x') + 120 + + + + + + + chr + + chr ( integer ) + text + + + Returns the character with the given code. In UTF8 + encoding the argument is treated as a Unicode code point. In other + multibyte encodings the argument must designate + an ASCII character. chr(0) is + disallowed because text data types cannot store that character. + + + chr(65) + A + + + + + + + concat + + concat ( val1 "any" + , val2 "any" , ... ) + text + + + Concatenates the text representations of all the arguments. + NULL arguments are ignored. + + + concat('abcde', 2, NULL, 22) + abcde222 + + + + + + + concat_ws + + concat_ws ( sep text, + val1 "any" + , val2 "any" , ... ) + text + + + Concatenates all but the first argument, with separators. The first + argument is used as the separator string, and should not be NULL. + Other NULL arguments are ignored. + + + concat_ws(',', 'abcde', 2, NULL, 22) + abcde,2,22 + + + + + + + format + + format ( formatstr text + , formatarg "any" , ... ) + text + + + Formats arguments according to a format string; + see . + This function is similar to the C function sprintf. + + + format('Hello %s, %1$s', 'World') + Hello World, World + + + + + + + initcap + + initcap ( text ) + text + + + Converts the first letter of each word to upper case and the + rest to lower case. When using the libc locale + provider, words are sequences of alphanumeric characters separated + by non-alphanumeric characters; when using the ICU locale provider, + words are separated according to + Unicode Standard Annex #29. + + + initcap('hi THOMAS') + Hi Thomas + + + + + + + casefold + + casefold ( text ) + text + + + Performs case folding of the input string according to the collation. + Case folding is similar to case conversion, but the purpose of case + folding is to facilitate case-insensitive matching of strings, + whereas the purpose of case conversion is to convert to a particular + cased form. This function can only be used when the server encoding + is UTF8. + + + Ordinarily, case folding simply converts to lowercase, but there may + be exceptions depending on the collation. For instance, some + characters have more than two lowercase variants, or fold to uppercase. + + + Case folding may change the length of the string. For instance, in + the PG_UNICODE_FAST collation, Ã + (U+00DF) folds to ss. + + + casefold can be used for Unicode Default Caseless + Matching. It does not always preserve the normalized form of the + input string (see ). + + + The libc provider doesn't support case folding, so + casefold is identical to . + + + + + + + left + + left ( string text, + n integer ) + text + + + Returns first n characters in the + string, or when n is negative, returns + all but last |n| characters. + + + left('abcde', 2) + ab + + + + + + + length + + length ( text ) + integer + + + Returns the number of characters in the string. + + + length('jose') + 4 + + + + + + + md5 + + md5 ( text ) + text + + + Computes the MD5 hash of + the argument, with the result written in hexadecimal. + + + md5('abc') + 900150983cd24fb0&zwsp;d6963f7d28e17f72 + + + + + + + parse_ident + + parse_ident ( qualified_identifier text + , strict_mode boolean DEFAULT true ) + text[] + + + Splits qualified_identifier into an array of + identifiers, removing any quoting of individual identifiers. By + default, extra characters after the last identifier are considered an + error; but if the second parameter is false, then such + extra characters are ignored. (This behavior is useful for parsing + names for objects like functions.) Note that this function does not + truncate over-length identifiers. If you want truncation you can cast + the result to name[]. + + + parse_ident('"SomeSchema".someTable') + {SomeSchema,sometable} + + + + + + + pg_client_encoding + + pg_client_encoding ( ) + name + + + Returns current client encoding name. + + + pg_client_encoding() + UTF8 + + + + + + + quote_ident + + quote_ident ( text ) + text + + + Returns the given string suitably quoted to be used as an identifier + in an SQL statement string. + Quotes are added only if necessary (i.e., if the string contains + non-identifier characters or would be case-folded). + Embedded quotes are properly doubled. + See also . + + + quote_ident('Foo bar') + "Foo bar" + + + + + + + quote_literal + + quote_literal ( text ) + text + + + Returns the given string suitably quoted to be used as a string literal + in an SQL statement string. + Embedded single-quotes and backslashes are properly doubled. + Note that quote_literal returns null on null + input; if the argument might be null, + quote_nullable is often more suitable. + See also . + + + quote_literal(E'O\'Reilly') + 'O''Reilly' + + + + + + quote_literal ( anyelement ) + text + + + Converts the given value to text and then quotes it as a literal. + Embedded single-quotes and backslashes are properly doubled. + + + quote_literal(42.5) + '42.5' + + + + + + + quote_nullable + + quote_nullable ( text ) + text + + + Returns the given string suitably quoted to be used as a string literal + in an SQL statement string; or, if the argument + is null, returns NULL. + Embedded single-quotes and backslashes are properly doubled. + See also . + + + quote_nullable(NULL) + NULL + + + + + + quote_nullable ( anyelement ) + text + + + Converts the given value to text and then quotes it as a literal; + or, if the argument is null, returns NULL. + Embedded single-quotes and backslashes are properly doubled. + + + quote_nullable(42.5) + '42.5' + + + + + + + regexp_count + + regexp_count ( string text, pattern text + , start integer + , flags text ) + integer + + + Returns the number of times the POSIX regular + expression pattern matches in + the string; see + . + + + regexp_count('123456789012', '\d\d\d', 2) + 3 + + + + + + + regexp_instr + + regexp_instr ( string text, pattern text + , start integer + , N integer + , endoption integer + , flags text + , subexpr integer ) + integer + + + Returns the position within string where + the N'th match of the POSIX regular + expression pattern occurs, or zero if there is + no such match; see . + + + regexp_instr('ABCDEF', 'c(.)(..)', 1, 1, 0, 'i') + 3 + + + regexp_instr('ABCDEF', 'c(.)(..)', 1, 1, 0, 'i', 2) + 5 + + + + + + + regexp_like + + regexp_like ( string text, pattern text + , flags text ) + boolean + + + Checks whether a match of the POSIX regular + expression pattern occurs + within string; see + . + + + regexp_like('Hello World', 'world$', 'i') + t + + + + + + + regexp_match + + regexp_match ( string text, pattern text , flags text ) + text[] + + + Returns substrings within the first match of the POSIX regular + expression pattern to + the string; see + . + + + regexp_match('foobarbequebaz', '(bar)(beque)') + {bar,beque} + + + + + + + regexp_matches + + regexp_matches ( string text, pattern text , flags text ) + setof text[] + + + Returns substrings within the first match of the POSIX regular + expression pattern to + the string, or substrings within all + such matches if the g flag is used; + see . + + + regexp_matches('foobarbequebaz', 'ba.', 'g') + + + {bar} + {baz} + + + + + + + + regexp_replace + + regexp_replace ( string text, pattern text, replacement text + , flags text ) + text + + + Replaces the substring that is the first match to the POSIX + regular expression pattern, or all such + matches if the g flag is used; see + . + + + regexp_replace('Thomas', '.[mN]a.', 'M') + ThM + + + + + + regexp_replace ( string text, pattern text, replacement text, + start integer + , N integer + , flags text ) + text + + + Replaces the substring that is the N'th + match to the POSIX regular expression pattern, + or all such matches if N is zero, with the + search beginning at the start'th character + of string. If N is + omitted, it defaults to 1. See + . + + + regexp_replace('Thomas', '.', 'X', 3, 2) + ThoXas + + + regexp_replace(string=>'hello world', pattern=>'l', replacement=>'XX', start=>1, "N"=>2) + helXXo world + + + + + + + regexp_split_to_array + + regexp_split_to_array ( string text, pattern text , flags text ) + text[] + + + Splits string using a POSIX regular + expression as the delimiter, producing an array of results; see + . + + + regexp_split_to_array('hello world', '\s+') + {hello,world} + + + + + + + regexp_split_to_table + + regexp_split_to_table ( string text, pattern text , flags text ) + setof text + + + Splits string using a POSIX regular + expression as the delimiter, producing a set of results; see + . + + + regexp_split_to_table('hello world', '\s+') + + + hello + world + + + + + + + + regexp_substr + + regexp_substr ( string text, pattern text + , start integer + , N integer + , flags text + , subexpr integer ) + text + + + Returns the substring within string that + matches the N'th occurrence of the POSIX + regular expression pattern, + or NULL if there is no such match; see + . + + + regexp_substr('ABCDEF', 'c(.)(..)', 1, 1, 'i') + CDEF + + + regexp_substr('ABCDEF', 'c(.)(..)', 1, 1, 'i', 2) + EF + + + + + + + repeat + + repeat ( string text, number integer ) + text + + + Repeats string the specified + number of times. + + + repeat('Pg', 4) + PgPgPgPg + + + + + + + replace + + replace ( string text, + from text, + to text ) + text + + + Replaces all occurrences in string of + substring from with + substring to. + + + replace('abcdefabcdef', 'cd', 'XX') + abXXefabXXef + + + + + + + reverse + + reverse ( text ) + text + + + Reverses the order of the characters in the string. + + + reverse('abcde') + edcba + + + + + + + right + + right ( string text, + n integer ) + text + + + Returns last n characters in the string, + or when n is negative, returns all but + first |n| characters. + + + right('abcde', 2) + de + + + + + + + split_part + + split_part ( string text, + delimiter text, + n integer ) + text + + + Splits string at occurrences + of delimiter and returns + the n'th field (counting from one), + or when n is negative, returns + the |n|'th-from-last field. + + + split_part('abc~@~def~@~ghi', '~@~', 2) + def + + + split_part('abc,def,ghi,jkl', ',', -2) + ghi + + + + + + + starts_with + + starts_with ( string text, prefix text ) + boolean + + + Returns true if string starts + with prefix. + + + starts_with('alphabet', 'alph') + t + + + + + + + string_to_array + + string_to_array ( string text, delimiter text , null_string text ) + text[] + + + Splits the string at occurrences + of delimiter and forms the resulting fields + into a text array. + If delimiter is NULL, + each character in the string will become a + separate element in the array. + If delimiter is an empty string, then + the string is treated as a single field. + If null_string is supplied and is + not NULL, fields matching that string are + replaced by NULL. + See also array_to_string. + + + string_to_array('xx~~yy~~zz', '~~', 'yy') + {xx,NULL,zz} + + + + + + + string_to_table + + string_to_table ( string text, delimiter text , null_string text ) + setof text + + + Splits the string at occurrences + of delimiter and returns the resulting fields + as a set of text rows. + If delimiter is NULL, + each character in the string will become a + separate row of the result. + If delimiter is an empty string, then + the string is treated as a single field. + If null_string is supplied and is + not NULL, fields matching that string are + replaced by NULL. + + + string_to_table('xx~^~yy~^~zz', '~^~', 'yy') + + + xx + NULL + zz + + + + + + + + strpos + + strpos ( string text, substring text ) + integer + + + Returns first starting index of the specified substring + within string, or zero if it's not present. + (Same as position(substring in + string), but note the reversed + argument order.) + + + strpos('high', 'ig') + 2 + + + + + + + substr + + substr ( string text, start integer , count integer ) + text + + + Extracts the substring of string starting at + the start'th character, + and extending for count characters if that is + specified. (Same + as substring(string + from start + for count).) + + + substr('alphabet', 3) + phabet + + + substr('alphabet', 3, 2) + ph + + + + + + + to_ascii + + to_ascii ( string text ) + text + + + to_ascii ( string text, + encoding name ) + text + + + to_ascii ( string text, + encoding integer ) + text + + + Converts string to ASCII + from another encoding, which may be identified by name or number. + If encoding is omitted the database encoding + is assumed (which in practice is the only useful case). + The conversion consists primarily of dropping accents. + Conversion is only supported + from LATIN1, LATIN2, + LATIN9, and WIN1250 encodings. + (See the module for another, more flexible + solution.) + + + to_ascii('Karél') + Karel + + + + + + + to_bin + + to_bin ( integer ) + text + + + to_bin ( bigint ) + text + + + Converts the number to its equivalent two's complement binary + representation. + + + to_bin(2147483647) + 1111111111111111111111111111111 + + + to_bin(-1234) + 11111111111111111111101100101110 + + + + + + + to_hex + + to_hex ( integer ) + text + + + to_hex ( bigint ) + text + + + Converts the number to its equivalent two's complement hexadecimal + representation. + + + to_hex(2147483647) + 7fffffff + + + to_hex(-1234) + fffffb2e + + + + + + + to_oct + + to_oct ( integer ) + text + + + to_oct ( bigint ) + text + + + Converts the number to its equivalent two's complement octal + representation. + + + to_oct(2147483647) + 17777777777 + + + to_oct(-1234) + 37777775456 + + + + + + + translate + + translate ( string text, + from text, + to text ) + text + + + Replaces each character in string that + matches a character in the from set with the + corresponding character in the to + set. If from is longer than + to, occurrences of the extra characters in + from are deleted. + + + translate('12345', '143', 'ax') + a2x5 + + + + + + + unistr + + unistr ( text ) + text + + + Evaluate escaped Unicode characters in the argument. Unicode characters + can be specified as + \XXXX (4 hexadecimal + digits), \+XXXXXX (6 + hexadecimal digits), + \uXXXX (4 hexadecimal + digits), or \UXXXXXXXX + (8 hexadecimal digits). To specify a backslash, write two + backslashes. All other characters are taken literally. + + + + If the server encoding is not UTF-8, the Unicode code point identified + by one of these escape sequences is converted to the actual server + encoding; an error is reported if that's not possible. + + + + This function provides a (non-standard) alternative to string + constants with Unicode escapes (see ). + + + + unistr('d\0061t\+000061') + data + + + unistr('d\u0061t\U00000061') + data + + + + + +

+ + + The concat, concat_ws and + format functions are variadic, so it is possible to + pass the values to be concatenated or formatted as an array marked with + the VARIADIC keyword (see ). The array's elements are + treated as if they were separate ordinary arguments to the function. + If the variadic array argument is NULL, concat + and concat_ws return NULL, but + format treats a NULL as a zero-element array. + + + + See also the aggregate function string_agg in + , and the functions for + converting between strings and the bytea type in + . + + + + <function>format</function> + + + format + + + + The function format produces output formatted according to + a format string, in a style similar to the C function + sprintf. + + + + +format(formatstr text , formatarg "any" , ... ) + + formatstr is a format string that specifies how the + result should be formatted. Text in the format string is copied + directly to the result, except where format specifiers are + used. Format specifiers act as placeholders in the string, defining how + subsequent function arguments should be formatted and inserted into the + result. Each formatarg argument is converted to text + according to the usual output rules for its data type, and then formatted + and inserted into the result string according to the format specifier(s). + + + + Format specifiers are introduced by a % character and have + the form + +%[position][flags][width]type + + where the component fields are: + + + + position (optional) + + + A string of the form n$ where + n is the index of the argument to print. + Index 1 means the first argument after + formatstr. If the position is + omitted, the default is to use the next argument in sequence. + + + + + + flags (optional) + + + Additional options controlling how the format specifier's output is + formatted. Currently the only supported flag is a minus sign + (-) which will cause the format specifier's output to be + left-justified. This has no effect unless the width + field is also specified. + + + + + + width (optional) + + + Specifies the minimum number of characters to use to + display the format specifier's output. The output is padded on the + left or right (depending on the - flag) with spaces as + needed to fill the width. A too-small width does not cause + truncation of the output, but is simply ignored. The width may be + specified using any of the following: a positive integer; an + asterisk (*) to use the next function argument as the + width; or a string of the form *n$ to + use the nth function argument as the width. + + + + If the width comes from a function argument, that argument is + consumed before the argument that is used for the format specifier's + value. If the width argument is negative, the result is left + aligned (as if the - flag had been specified) within a + field of length abs(width). + + + + + + type (required) + + + The type of format conversion to use to produce the format + specifier's output. The following types are supported: + + + + s formats the argument value as a simple + string. A null value is treated as an empty string. + + + + + I treats the argument value as an SQL + identifier, double-quoting it if necessary. + It is an error for the value to be null (equivalent to + quote_ident). + + + + + L quotes the argument value as an SQL literal. + A null value is displayed as the string NULL, without + quotes (equivalent to quote_nullable). + + + + + + + + + + + In addition to the format specifiers described above, the special sequence + %% may be used to output a literal % character. + + + + Here are some examples of the basic format conversions: + + +SELECT format('Hello %s', 'World'); +Result: Hello World + +SELECT format('Testing %s, %s, %s, %%', 'one', 'two', 'three'); +Result: Testing one, two, three, % + +SELECT format('INSERT INTO %I VALUES(%L)', 'Foo bar', E'O\'Reilly'); +Result: INSERT INTO "Foo bar" VALUES('O''Reilly') + +SELECT format('INSERT INTO %I VALUES(%L)', 'locations', 'C:\Program Files'); +Result: INSERT INTO locations VALUES('C:\Program Files') + + + + + Here are examples using width fields + and the - flag: + + +SELECT format('|%10s|', 'foo'); +Result: | foo| + +SELECT format('|%-10s|', 'foo'); +Result: |foo | + +SELECT format('|%*s|', 10, 'foo'); +Result: | foo| + +SELECT format('|%*s|', -10, 'foo'); +Result: |foo | + +SELECT format('|%-*s|', 10, 'foo'); +Result: |foo | + +SELECT format('|%-*s|', -10, 'foo'); +Result: |foo | + + + + + These examples show use of position fields: + + +SELECT format('Testing %3$s, %2$s, %1$s', 'one', 'two', 'three'); +Result: Testing three, two, one + +SELECT format('|%*2$s|', 'foo', 10, 'bar'); +Result: | bar| + +SELECT format('|%1$*2$s|', 'foo', 10, 'bar'); +Result: | foo| + + + + + Unlike the standard C function sprintf, + PostgreSQL's format function allows format + specifiers with and without position fields to be mixed + in the same format string. A format specifier without a + position field always uses the next argument after the + last argument consumed. + In addition, the format function does not require all + function arguments to be used in the format string. + For example: + + +SELECT format('Testing %3$s, %2$s, %s', 'one', 'two', 'three'); +Result: Testing three, two, three + + + + + The %I and %L format specifiers are particularly + useful for safely constructing dynamic SQL statements. See + . + + + + diff --git a/doc/src/sgml/func/func-subquery.sgml b/doc/src/sgml/func/func-subquery.sgml new file mode 100644 index 00000000000..a9f2b12e48c --- /dev/null +++ b/doc/src/sgml/func/func-subquery.sgml @@ -0,0 +1,349 @@ + + Subquery Expressions + + + EXISTS + + + + IN + + + + NOT IN + + + + ANY + + + + ALL + + + + SOME + + + + subquery + + + + This section describes the SQL-compliant subquery + expressions available in PostgreSQL. + All of the expression forms documented in this section return + Boolean (true/false) results. + + + + <literal>EXISTS</literal> + + +EXISTS (subquery) + + + + The argument of EXISTS is an arbitrary SELECT statement, + or subquery. The + subquery is evaluated to determine whether it returns any rows. + If it returns at least one row, the result of EXISTS is + true; if the subquery returns no rows, the result of EXISTS + is false. + + + + The subquery can refer to variables from the surrounding query, + which will act as constants during any one evaluation of the subquery. + + + + The subquery will generally only be executed long enough to determine + whether at least one row is returned, not all the way to completion. + It is unwise to write a subquery that has side effects (such as + calling sequence functions); whether the side effects occur + might be unpredictable. + + + + Since the result depends only on whether any rows are returned, + and not on the contents of those rows, the output list of the + subquery is normally unimportant. A common coding convention is + to write all EXISTS tests in the form + EXISTS(SELECT 1 WHERE ...). There are exceptions to + this rule however, such as subqueries that use INTERSECT. + + + + This simple example is like an inner join on col2, but + it produces at most one output row for each tab1 row, + even if there are several matching tab2 rows: + +SELECT col1 +FROM tab1 +WHERE EXISTS (SELECT 1 FROM tab2 WHERE col2 = tab1.col2); + + + + + + <literal>IN</literal> + + +expression IN (subquery) + + + + The right-hand side is a parenthesized + subquery, which must return exactly one column. The left-hand expression + is evaluated and compared to each row of the subquery result. + The result of IN is true if any equal subquery row is found. + The result is false if no equal row is found (including the + case where the subquery returns no rows). + + + + Note that if the left-hand expression yields null, or if there are + no equal right-hand values and at least one right-hand row yields + null, the result of the IN construct will be null, not false. + This is in accordance with SQL's normal rules for Boolean combinations + of null values. + + + + As with EXISTS, it's unwise to assume that the subquery will + be evaluated completely. + + + +row_constructor IN (subquery) + + + + The left-hand side of this form of IN is a row constructor, + as described in . + The right-hand side is a parenthesized + subquery, which must return exactly as many columns as there are + expressions in the left-hand row. The left-hand expressions are + evaluated and compared row-wise to each row of the subquery result. + The result of IN is true if any equal subquery row is found. + The result is false if no equal row is found (including the + case where the subquery returns no rows). + + + + As usual, null values in the rows are combined per + the normal rules of SQL Boolean expressions. Two rows are considered + equal if all their corresponding members are non-null and equal; the rows + are unequal if any corresponding members are non-null and unequal; + otherwise the result of that row comparison is unknown (null). + If all the per-row results are either unequal or null, with at least one + null, then the result of IN is null. + + + + + <literal>NOT IN</literal> + + +expression NOT IN (subquery) + + + + The right-hand side is a parenthesized + subquery, which must return exactly one column. The left-hand expression + is evaluated and compared to each row of the subquery result. + The result of NOT IN is true if only unequal subquery rows + are found (including the case where the subquery returns no rows). + The result is false if any equal row is found. + + + + Note that if the left-hand expression yields null, or if there are + no equal right-hand values and at least one right-hand row yields + null, the result of the NOT IN construct will be null, not true. + This is in accordance with SQL's normal rules for Boolean combinations + of null values. + + + + As with EXISTS, it's unwise to assume that the subquery will + be evaluated completely. + + + +row_constructor NOT IN (subquery) + + + + The left-hand side of this form of NOT IN is a row constructor, + as described in . + The right-hand side is a parenthesized + subquery, which must return exactly as many columns as there are + expressions in the left-hand row. The left-hand expressions are + evaluated and compared row-wise to each row of the subquery result. + The result of NOT IN is true if only unequal subquery rows + are found (including the case where the subquery returns no rows). + The result is false if any equal row is found. + + + + As usual, null values in the rows are combined per + the normal rules of SQL Boolean expressions. Two rows are considered + equal if all their corresponding members are non-null and equal; the rows + are unequal if any corresponding members are non-null and unequal; + otherwise the result of that row comparison is unknown (null). + If all the per-row results are either unequal or null, with at least one + null, then the result of NOT IN is null. + + + + + <literal>ANY</literal>/<literal>SOME</literal> + + +expression operator ANY (subquery) +expression operator SOME (subquery) + + + + The right-hand side is a parenthesized + subquery, which must return exactly one column. The left-hand expression + is evaluated and compared to each row of the subquery result using the + given operator, which must yield a Boolean + result. + The result of ANY is true if any true result is obtained. + The result is false if no true result is found (including the + case where the subquery returns no rows). + + + + SOME is a synonym for ANY. + IN is equivalent to = ANY. + + + + Note that if there are no successes and at least one right-hand row yields + null for the operator's result, the result of the ANY construct + will be null, not false. + This is in accordance with SQL's normal rules for Boolean combinations + of null values. + + + + As with EXISTS, it's unwise to assume that the subquery will + be evaluated completely. + + + +row_constructor operator ANY (subquery) +row_constructor operator SOME (subquery) + + + + The left-hand side of this form of ANY is a row constructor, + as described in . + The right-hand side is a parenthesized + subquery, which must return exactly as many columns as there are + expressions in the left-hand row. The left-hand expressions are + evaluated and compared row-wise to each row of the subquery result, + using the given operator. + The result of ANY is true if the comparison + returns true for any subquery row. + The result is false if the comparison returns false for every + subquery row (including the case where the subquery returns no + rows). + The result is NULL if no comparison with a subquery row returns true, + and at least one comparison returns NULL. + + + + See for details about the meaning + of a row constructor comparison. + + + + + <literal>ALL</literal> + + +expression operator ALL (subquery) + + + + The right-hand side is a parenthesized + subquery, which must return exactly one column. The left-hand expression + is evaluated and compared to each row of the subquery result using the + given operator, which must yield a Boolean + result. + The result of ALL is true if all rows yield true + (including the case where the subquery returns no rows). + The result is false if any false result is found. + The result is NULL if no comparison with a subquery row returns false, + and at least one comparison returns NULL. + + + + NOT IN is equivalent to <> ALL. + + + + As with EXISTS, it's unwise to assume that the subquery will + be evaluated completely. + + + +row_constructor operator ALL (subquery) + + + + The left-hand side of this form of ALL is a row constructor, + as described in . + The right-hand side is a parenthesized + subquery, which must return exactly as many columns as there are + expressions in the left-hand row. The left-hand expressions are + evaluated and compared row-wise to each row of the subquery result, + using the given operator. + The result of ALL is true if the comparison + returns true for all subquery rows (including the + case where the subquery returns no rows). + The result is false if the comparison returns false for any + subquery row. + The result is NULL if no comparison with a subquery row returns false, + and at least one comparison returns NULL. + + + + See for details about the meaning + of a row constructor comparison. + + + + + Single-Row Comparison + + + comparison + subquery result row + + + +row_constructor operator (subquery) + + + + The left-hand side is a row constructor, + as described in . + The right-hand side is a parenthesized subquery, which must return exactly + as many columns as there are expressions in the left-hand row. Furthermore, + the subquery cannot return more than one row. (If it returns zero rows, + the result is taken to be null.) The left-hand side is evaluated and + compared row-wise to the single subquery result row. + + + + See for details about the meaning + of a row constructor comparison. + + + diff --git a/doc/src/sgml/func/func-textsearch.sgml b/doc/src/sgml/func/func-textsearch.sgml new file mode 100644 index 00000000000..a06a58f1498 --- /dev/null +++ b/doc/src/sgml/func/func-textsearch.sgml @@ -0,0 +1,1046 @@ + + Text Search Functions and Operators + + + full text search + functions and operators + + + + text search + functions and operators + + + + , + and + + summarize the functions and operators that are provided + for full text searching. See for a detailed + explanation of PostgreSQL's text search + facility. + + + + Text Search Operators + + + + + Operator + + + Description + + + Example(s) + + + + + + + + tsvector @@ tsquery + boolean + + + tsquery @@ tsvector + boolean + + + Does tsvector match tsquery? + (The arguments can be given in either order.) + + + to_tsvector('fat cats ate rats') @@ to_tsquery('cat & rat') + t + + + + + + text @@ tsquery + boolean + + + Does text string, after implicit invocation + of to_tsvector(), match tsquery? + + + 'fat cats ate rats' @@ to_tsquery('cat & rat') + t + + + + + + tsvector || tsvector + tsvector + + + Concatenates two tsvectors. If both inputs contain + lexeme positions, the second input's positions are adjusted + accordingly. + + + 'a:1 b:2'::tsvector || 'c:1 d:2 b:3'::tsvector + 'a':1 'b':2,5 'c':3 'd':4 + + + + + + tsquery && tsquery + tsquery + + + ANDs two tsquerys together, producing a query that + matches documents that match both input queries. + + + 'fat | rat'::tsquery && 'cat'::tsquery + ( 'fat' | 'rat' ) & 'cat' + + + + + + tsquery || tsquery + tsquery + + + ORs two tsquerys together, producing a query that + matches documents that match either input query. + + + 'fat | rat'::tsquery || 'cat'::tsquery + 'fat' | 'rat' | 'cat' + + + + + + !! tsquery + tsquery + + + Negates a tsquery, producing a query that matches + documents that do not match the input query. + + + !! 'cat'::tsquery + !'cat' + + + + + + tsquery <-> tsquery + tsquery + + + Constructs a phrase query, which matches if the two input queries + match at successive lexemes. + + + to_tsquery('fat') <-> to_tsquery('rat') + 'fat' <-> 'rat' + + + + + + tsquery @> tsquery + boolean + + + Does first tsquery contain the second? (This considers + only whether all the lexemes appearing in one query appear in the + other, ignoring the combining operators.) + + + 'cat'::tsquery @> 'cat & rat'::tsquery + f + + + + + + tsquery <@ tsquery + boolean + + + Is first tsquery contained in the second? (This + considers only whether all the lexemes appearing in one query appear + in the other, ignoring the combining operators.) + + + 'cat'::tsquery <@ 'cat & rat'::tsquery + t + + + 'cat'::tsquery <@ '!cat & rat'::tsquery + t + + + + +

+ + + In addition to these specialized operators, the usual comparison + operators shown in are + available for types tsvector and tsquery. + These are not very + useful for text searching but allow, for example, unique indexes to be + built on columns of these types. + + + + Text Search Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + array_to_tsvector + + array_to_tsvector ( text[] ) + tsvector + + + Converts an array of text strings to a tsvector. + The given strings are used as lexemes as-is, without further + processing. Array elements must not be empty strings + or NULL. + + + array_to_tsvector('{fat,cat,rat}'::text[]) + 'cat' 'fat' 'rat' + + + + + + + get_current_ts_config + + get_current_ts_config ( ) + regconfig + + + Returns the OID of the current default text search configuration + (as set by ). + + + get_current_ts_config() + english + + + + + + + length + + length ( tsvector ) + integer + + + Returns the number of lexemes in the tsvector. + + + length('fat:2,4 cat:3 rat:5A'::tsvector) + 3 + + + + + + + numnode + + numnode ( tsquery ) + integer + + + Returns the number of lexemes plus operators in + the tsquery. + + + numnode('(fat & rat) | cat'::tsquery) + 5 + + + + + + + plainto_tsquery + + plainto_tsquery ( + config regconfig, + query text ) + tsquery + + + Converts text to a tsquery, normalizing words according to + the specified or default configuration. Any punctuation in the string + is ignored (it does not determine query operators). The resulting + query matches documents containing all non-stopwords in the text. + + + plainto_tsquery('english', 'The Fat Rats') + 'fat' & 'rat' + + + + + + + phraseto_tsquery + + phraseto_tsquery ( + config regconfig, + query text ) + tsquery + + + Converts text to a tsquery, normalizing words according to + the specified or default configuration. Any punctuation in the string + is ignored (it does not determine query operators). The resulting + query matches phrases containing all non-stopwords in the text. + + + phraseto_tsquery('english', 'The Fat Rats') + 'fat' <-> 'rat' + + + phraseto_tsquery('english', 'The Cat and Rats') + 'cat' <2> 'rat' + + + + + + + websearch_to_tsquery + + websearch_to_tsquery ( + config regconfig, + query text ) + tsquery + + + Converts text to a tsquery, normalizing words according + to the specified or default configuration. Quoted word sequences are + converted to phrase tests. The word or is understood + as producing an OR operator, and a dash produces a NOT operator; + other punctuation is ignored. + This approximates the behavior of some common web search tools. + + + websearch_to_tsquery('english', '"fat rat" or cat dog') + 'fat' <-> 'rat' | 'cat' & 'dog' + + + + + + + querytree + + querytree ( tsquery ) + text + + + Produces a representation of the indexable portion of + a tsquery. A result that is empty or + just T indicates a non-indexable query. + + + querytree('foo & ! bar'::tsquery) + 'foo' + + + + + + + setweight + + setweight ( vector tsvector, weight "char" ) + tsvector + + + Assigns the specified weight to each element + of the vector. + + + setweight('fat:2,4 cat:3 rat:5B'::tsvector, 'A') + 'cat':3A 'fat':2A,4A 'rat':5A + + + + + + + setweight + setweight for specific lexeme(s) + + setweight ( vector tsvector, weight "char", lexemes text[] ) + tsvector + + + Assigns the specified weight to elements + of the vector that are listed + in lexemes. + The strings in lexemes are taken as lexemes + as-is, without further processing. Strings that do not match any + lexeme in vector are ignored. + + + setweight('fat:2,4 cat:3 rat:5,6B'::tsvector, 'A', '{cat,rat}') + 'cat':3A 'fat':2,4 'rat':5A,6A + + + + + + + strip + + strip ( tsvector ) + tsvector + + + Removes positions and weights from the tsvector. + + + strip('fat:2,4 cat:3 rat:5A'::tsvector) + 'cat' 'fat' 'rat' + + + + + + + to_tsquery + + to_tsquery ( + config regconfig, + query text ) + tsquery + + + Converts text to a tsquery, normalizing words according to + the specified or default configuration. The words must be combined + by valid tsquery operators. + + + to_tsquery('english', 'The & Fat & Rats') + 'fat' & 'rat' + + + + + + + to_tsvector + + to_tsvector ( + config regconfig, + document text ) + tsvector + + + Converts text to a tsvector, normalizing words according + to the specified or default configuration. Position information is + included in the result. + + + to_tsvector('english', 'The Fat Rats') + 'fat':2 'rat':3 + + + + + + to_tsvector ( + config regconfig, + document json ) + tsvector + + + to_tsvector ( + config regconfig, + document jsonb ) + tsvector + + + Converts each string value in the JSON document to + a tsvector, normalizing words according to the specified + or default configuration. The results are then concatenated in + document order to produce the output. Position information is + generated as though one stopword exists between each pair of string + values. (Beware that document order of the fields of a + JSON object is implementation-dependent when the input + is jsonb; observe the difference in the examples.) + + + to_tsvector('english', '{"aa": "The Fat Rats", "b": "dog"}'::json) + 'dog':5 'fat':2 'rat':3 + + + to_tsvector('english', '{"aa": "The Fat Rats", "b": "dog"}'::jsonb) + 'dog':1 'fat':4 'rat':5 + + + + + + + json_to_tsvector + + json_to_tsvector ( + config regconfig, + document json, + filter jsonb ) + tsvector + + + + jsonb_to_tsvector + + jsonb_to_tsvector ( + config regconfig, + document jsonb, + filter jsonb ) + tsvector + + + Selects each item in the JSON document that is requested by + the filter and converts each one to + a tsvector, normalizing words according to the specified + or default configuration. The results are then concatenated in + document order to produce the output. Position information is + generated as though one stopword exists between each pair of selected + items. (Beware that document order of the fields of a + JSON object is implementation-dependent when the input + is jsonb.) + The filter must be a jsonb + array containing zero or more of these keywords: + "string" (to include all string values), + "numeric" (to include all numeric values), + "boolean" (to include all boolean values), + "key" (to include all keys), or + "all" (to include all the above). + As a special case, the filter can also be a + simple JSON value that is one of these keywords. + + + json_to_tsvector('english', '{"a": "The Fat Rats", "b": 123}'::json, '["string", "numeric"]') + '123':5 'fat':2 'rat':3 + + + json_to_tsvector('english', '{"cat": "The Fat Rats", "dog": 123}'::json, '"all"') + '123':9 'cat':1 'dog':7 'fat':4 'rat':5 + + + + + + + ts_delete + + ts_delete ( vector tsvector, lexeme text ) + tsvector + + + Removes any occurrence of the given lexeme + from the vector. + The lexeme string is treated as a lexeme as-is, + without further processing. + + + ts_delete('fat:2,4 cat:3 rat:5A'::tsvector, 'fat') + 'cat':3 'rat':5A + + + + + + ts_delete ( vector tsvector, lexemes text[] ) + tsvector + + + Removes any occurrences of the lexemes + in lexemes + from the vector. + The strings in lexemes are taken as lexemes + as-is, without further processing. Strings that do not match any + lexeme in vector are ignored. + + + ts_delete('fat:2,4 cat:3 rat:5A'::tsvector, ARRAY['fat','rat']) + 'cat':3 + + + + + + + ts_filter + + ts_filter ( vector tsvector, weights "char"[] ) + tsvector + + + Selects only elements with the given weights + from the vector. + + + ts_filter('fat:2,4 cat:3b,7c rat:5A'::tsvector, '{a,b}') + 'cat':3B 'rat':5A + + + + + + + ts_headline + + ts_headline ( + config regconfig, + document text, + query tsquery + , options text ) + text + + + Displays, in an abbreviated form, the match(es) for + the query in + the document, which must be raw text not + a tsvector. Words in the document are normalized + according to the specified or default configuration before matching to + the query. Use of this function is discussed in + , which also describes the + available options. + + + ts_headline('The fat cat ate the rat.', 'cat') + The fat cat ate the rat. + + + + + + ts_headline ( + config regconfig, + document json, + query tsquery + , options text ) + text + + + ts_headline ( + config regconfig, + document jsonb, + query tsquery + , options text ) + text + + + Displays, in an abbreviated form, match(es) for + the query that occur in string values + within the JSON document. + See for more details. + + + ts_headline('{"cat":"raining cats and dogs"}'::jsonb, 'cat') + {"cat": "raining cats and dogs"} + + + + + + + ts_rank + + ts_rank ( + weights real[], + vector tsvector, + query tsquery + , normalization integer ) + real + + + Computes a score showing how well + the vector matches + the query. See + for details. + + + ts_rank(to_tsvector('raining cats and dogs'), 'cat') + 0.06079271 + + + + + + + ts_rank_cd + + ts_rank_cd ( + weights real[], + vector tsvector, + query tsquery + , normalization integer ) + real + + + Computes a score showing how well + the vector matches + the query, using a cover density + algorithm. See for details. + + + ts_rank_cd(to_tsvector('raining cats and dogs'), 'cat') + 0.1 + + + + + + + ts_rewrite + + ts_rewrite ( query tsquery, + target tsquery, + substitute tsquery ) + tsquery + + + Replaces occurrences of target + with substitute + within the query. + See for details. + + + ts_rewrite('a & b'::tsquery, 'a'::tsquery, 'foo|bar'::tsquery) + 'b' & ( 'foo' | 'bar' ) + + + + + + ts_rewrite ( query tsquery, + select text ) + tsquery + + + Replaces portions of the query according to + target(s) and substitute(s) obtained by executing + a SELECT command. + See for details. + + + SELECT ts_rewrite('a & b'::tsquery, 'SELECT t,s FROM aliases') + 'b' & ( 'foo' | 'bar' ) + + + + + + + tsquery_phrase + + tsquery_phrase ( query1 tsquery, query2 tsquery ) + tsquery + + + Constructs a phrase query that searches + for matches of query1 + and query2 at successive lexemes (same + as <-> operator). + + + tsquery_phrase(to_tsquery('fat'), to_tsquery('cat')) + 'fat' <-> 'cat' + + + + + + tsquery_phrase ( query1 tsquery, query2 tsquery, distance integer ) + tsquery + + + Constructs a phrase query that searches + for matches of query1 and + query2 that occur exactly + distance lexemes apart. + + + tsquery_phrase(to_tsquery('fat'), to_tsquery('cat'), 10) + 'fat' <10> 'cat' + + + + + + + tsvector_to_array + + tsvector_to_array ( tsvector ) + text[] + + + Converts a tsvector to an array of lexemes. + + + tsvector_to_array('fat:2,4 cat:3 rat:5A'::tsvector) + {cat,fat,rat} + + + + + + + unnest + for tsvector + + unnest ( tsvector ) + setof record + ( lexeme text, + positions smallint[], + weights text ) + + + Expands a tsvector into a set of rows, one per lexeme. + + + select * from unnest('cat:3 fat:2,4 rat:5A'::tsvector) + + + lexeme | positions | weights +--------+-----------+--------- + cat | {3} | {D} + fat | {2,4} | {D,D} + rat | {5} | {A} + + + + + +

+ + + + All the text search functions that accept an optional regconfig + argument will use the configuration specified by + + when that argument is omitted. + + + + + The functions in + + are listed separately because they are not usually used in everyday text + searching operations. They are primarily helpful for development and + debugging of new text search configurations. + + + + Text Search Debugging Functions + + + + + Function + + + Description + + + Example(s) + + + + + + + + + ts_debug + + ts_debug ( + config regconfig, + document text ) + setof record + ( alias text, + description text, + token text, + dictionaries regdictionary[], + dictionary regdictionary, + lexemes text[] ) + + + Extracts and normalizes tokens from + the document according to the specified or + default text search configuration, and returns information about how + each token was processed. + See for details. + + + ts_debug('english', 'The Brightest supernovaes') + (asciiword,"Word, all ASCII",The,{english_stem},english_stem,{}) ... + + + + + + + ts_lexize + + ts_lexize ( dict regdictionary, token text ) + text[] + + + Returns an array of replacement lexemes if the input token is known to + the dictionary, or an empty array if the token is known to the + dictionary but it is a stop word, or NULL if it is not a known word. + See for details. + + + ts_lexize('english_stem', 'stars') + {star} + + + + + + + ts_parse + + ts_parse ( parser_name text, + document text ) + setof record + ( tokid integer, + token text ) + + + Extracts tokens from the document using the + named parser. + See for details. + + + ts_parse('default', 'foo - bar') + (1,foo) ... + + + + + + ts_parse ( parser_oid oid, + document text ) + setof record + ( tokid integer, + token text ) + + + Extracts tokens from the document using a + parser specified by OID. + See for details. + + + ts_parse(3722, 'foo - bar') + (1,foo) ... + + + + + + + ts_token_type + + ts_token_type ( parser_name text ) + setof record + ( tokid integer, + alias text, + description text ) + + + Returns a table that describes each type of token the named parser can + recognize. + See for details. + + + ts_token_type('default') + (1,asciiword,"Word, all ASCII") ... + + + + + + ts_token_type ( parser_oid oid ) + setof record + ( tokid integer, + alias text, + description text ) + + + Returns a table that describes each type of token a parser specified + by OID can recognize. + See for details. + + + ts_token_type(3722) + (1,asciiword,"Word, all ASCII") ... + + + + + + + ts_stat + + ts_stat ( sqlquery text + , weights text ) + setof record + ( word text, + ndoc integer, + nentry integer ) + + + Executes the sqlquery, which must return a + single tsvector column, and returns statistics about each + distinct lexeme contained in the data. + See for details. + + + ts_stat('SELECT vector FROM apod') + (foo,10,15) ... + + + + +

+ + diff --git a/doc/src/sgml/func/func-trigger.sgml b/doc/src/sgml/func/func-trigger.sgml new file mode 100644 index 00000000000..94b40adbdb8 --- /dev/null +++ b/doc/src/sgml/func/func-trigger.sgml @@ -0,0 +1,135 @@ + + Trigger Functions + + + While many uses of triggers involve user-written trigger functions, + PostgreSQL provides a few built-in trigger + functions that can be used directly in user-defined triggers. These + are summarized in . + (Additional built-in trigger functions exist, which implement foreign + key constraints and deferred index constraints. Those are not documented + here since users need not use them directly.) + + + + For more information about creating triggers, see + . + + + + Built-In Trigger Functions + + + + + Function + + + Description + + + Example Usage + + + + + + + + + suppress_redundant_updates_trigger + + suppress_redundant_updates_trigger ( ) + trigger + + + Suppresses do-nothing update operations. See below for details. + + + CREATE TRIGGER ... suppress_redundant_updates_trigger() + + + + + + + tsvector_update_trigger + + tsvector_update_trigger ( ) + trigger + + + Automatically updates a tsvector column from associated + plain-text document column(s). The text search configuration to use + is specified by name as a trigger argument. See + for details. + + + CREATE TRIGGER ... tsvector_update_trigger(tsvcol, 'pg_catalog.swedish', title, body) + + + + + + + tsvector_update_trigger_column + + tsvector_update_trigger_column ( ) + trigger + + + Automatically updates a tsvector column from associated + plain-text document column(s). The text search configuration to use + is taken from a regconfig column of the table. See + for details. + + + CREATE TRIGGER ... tsvector_update_trigger_column(tsvcol, tsconfigcol, title, body) + + + + +

+ + + The suppress_redundant_updates_trigger function, + when applied as a row-level BEFORE UPDATE trigger, + will prevent any update that does not actually change the data in the + row from taking place. This overrides the normal behavior which always + performs a physical row update + regardless of whether or not the data has changed. (This normal behavior + makes updates run faster, since no checking is required, and is also + useful in certain cases.) + + + + Ideally, you should avoid running updates that don't actually + change the data in the record. Redundant updates can cost considerable + unnecessary time, especially if there are lots of indexes to alter, + and space in dead rows that will eventually have to be vacuumed. + However, detecting such situations in client code is not + always easy, or even possible, and writing expressions to detect + them can be error-prone. An alternative is to use + suppress_redundant_updates_trigger, which will skip + updates that don't change the data. You should use this with care, + however. The trigger takes a small but non-trivial time for each record, + so if most of the records affected by updates do actually change, + use of this trigger will make updates run slower on average. + + + + The suppress_redundant_updates_trigger function can be + added to a table like this: + +CREATE TRIGGER z_min_update +BEFORE UPDATE ON tablename +FOR EACH ROW EXECUTE FUNCTION suppress_redundant_updates_trigger(); + + In most cases, you need to fire this trigger last for each row, so that + it does not override other triggers that might wish to alter the row. + Bearing in mind that triggers fire in name order, you would therefore + choose a trigger name that comes after the name of any other trigger + you might have on the table. (Hence the z prefix in the + example.) + + diff --git a/doc/src/sgml/func/func-uuid.sgml b/doc/src/sgml/func/func-uuid.sgml new file mode 100644 index 00000000000..65c5ddec6b7 --- /dev/null +++ b/doc/src/sgml/func/func-uuid.sgml @@ -0,0 +1,188 @@ + + UUID Functions + + + UUID + generating + + + + gen_random_uuid + + + + uuidv4 + + + + uuidv7 + + + + uuid_extract_timestamp + + + + uuid_extract_version + + + + shows the PostgreSQL + functions that can be used to generate UUIDs. + + + + <acronym>UUID</acronym> Generation Functions + + + + + + Function + + + Description + + + Example(s) + + + + + + + + + + gen_random_uuid + uuid + + + uuidv4 + uuid + + + Generate a version 4 (random) UUID. + + + gen_random_uuid() + 5b30857f-0bfa-48b5-ac0b-5c64e28078d1 + + + uuidv4() + b42410ee-132f-42ee-9e4f-09a6485c95b8 + + + + + + + uuidv7 + ( shift interval ) + uuid + + + Generate a version 7 (time-ordered) UUID. The timestamp is computed using UNIX timestamp + with millisecond precision + sub-millisecond timestamp + random. The optional parameter + shift will shift the computed timestamp by the given interval. + + + uuidv7() + 019535d9-3df7-79fb-b466-fa907fa17f9e + + + + + +

+ + + + The module provides additional functions that + implement other standard algorithms for generating UUIDs. + + + + + shows the PostgreSQL + functions that can be used to extract information from UUIDs. + + + + <acronym>UUID</acronym> Extraction Functions + + + + + + Function + + + Description + + + Example(s) + + + + + + + + + + uuid_extract_timestamp + ( uuid ) + timestamp with time zone + + + Extracts a timestamp with time zone from UUID + version 1 and 7. For other versions, this function returns null. Note that + the extracted timestamp is not necessarily exactly equal to the time the + UUID was generated; this depends on the implementation that generated the + UUID. + + + uuid_extract_timestamp('019535d9-3df7-79fb-b466-&zwsp;fa907fa17f9e'::uuid) + 2025-02-23 21:46:24.503-05 + + + + + + + uuid_extract_version + ( uuid ) + smallint + + + Extracts the version from a UUID of the variant described by + RFC 9562. For + other variants, this function returns null. For example, for a UUID + generated by gen_random_uuid, this function will + return 4. + + + uuid_extract_version('41db1265-8bc1-4ab3-992f-&zwsp;885799a4af1d'::uuid) + 4 + + + uuid_extract_version('019535d9-3df7-79fb-b466-&zwsp;fa907fa17f9e'::uuid) + 7 + + + + + +

+ + + PostgreSQL also provides the usual comparison + operators shown in for + UUIDs. + + + See for details on the data type + uuid in PostgreSQL. + + diff --git a/doc/src/sgml/func/func-window.sgml b/doc/src/sgml/func/func-window.sgml new file mode 100644 index 00000000000..cce0165b952 --- /dev/null +++ b/doc/src/sgml/func/func-window.sgml @@ -0,0 +1,284 @@ + + Window Functions + + + window function + built-in + + + + Window functions provide the ability to perform + calculations across sets of rows that are related to the current query + row. See for an introduction to this + feature, and for syntax + details. + + + + The built-in window functions are listed in + . Note that these functions + must be invoked using window function syntax, i.e., an + OVER clause is required. + + + + In addition to these functions, any built-in or user-defined + ordinary aggregate (i.e., not ordered-set or hypothetical-set aggregates) + can be used as a window function; see + for a list of the built-in aggregates. + Aggregate functions act as window functions only when an OVER + clause follows the call; otherwise they act as plain aggregates + and return a single row for the entire set. + + + + General-Purpose Window Functions + + + + + Function + + + Description + + + + + + + + + row_number + + row_number () + bigint + + + Returns the number of the current row within its partition, counting + from 1. + + + + + + + rank + + rank () + bigint + + + Returns the rank of the current row, with gaps; that is, + the row_number of the first row in its peer + group. + + + + + + + dense_rank + + dense_rank () + bigint + + + Returns the rank of the current row, without gaps; this function + effectively counts peer groups. + + + + + + + percent_rank + + percent_rank () + double precision + + + Returns the relative rank of the current row, that is + (rank - 1) / (total partition rows - 1). + The value thus ranges from 0 to 1 inclusive. + + + + + + + cume_dist + + cume_dist () + double precision + + + Returns the cumulative distribution, that is (number of partition rows + preceding or peers with current row) / (total partition rows). + The value thus ranges from 1/N to 1. + + + + + + + ntile + + ntile ( num_buckets integer ) + integer + + + Returns an integer ranging from 1 to the argument value, dividing the + partition as equally as possible. + + + + + + + lag + + lag ( value anycompatible + , offset integer + , default anycompatible ) + anycompatible + + + Returns value evaluated at + the row that is offset + rows before the current row within the partition; if there is no such + row, instead returns default + (which must be of a type compatible with + value). + Both offset and + default are evaluated + with respect to the current row. If omitted, + offset defaults to 1 and + default to NULL. + + + + + + + lead + + lead ( value anycompatible + , offset integer + , default anycompatible ) + anycompatible + + + Returns value evaluated at + the row that is offset + rows after the current row within the partition; if there is no such + row, instead returns default + (which must be of a type compatible with + value). + Both offset and + default are evaluated + with respect to the current row. If omitted, + offset defaults to 1 and + default to NULL. + + + + + + + first_value + + first_value ( value anyelement ) + anyelement + + + Returns value evaluated + at the row that is the first row of the window frame. + + + + + + + last_value + + last_value ( value anyelement ) + anyelement + + + Returns value evaluated + at the row that is the last row of the window frame. + + + + + + + nth_value + + nth_value ( value anyelement, n integer ) + anyelement + + + Returns value evaluated + at the row that is the n'th + row of the window frame (counting from 1); + returns NULL if there is no such row. + + + + +

+ + + All of the functions listed in + depend on the sort ordering + specified by the ORDER BY clause of the associated window + definition. Rows that are not distinct when considering only the + ORDER BY columns are said to be peers. + The four ranking functions (including cume_dist) are + defined so that they give the same answer for all rows of a peer group. + + + + Note that first_value, last_value, and + nth_value consider only the rows within the window + frame, which by default contains the rows from the start of the + partition through the last peer of the current row. This is + likely to give unhelpful results for last_value and + sometimes also nth_value. You can redefine the frame by + adding a suitable frame specification (RANGE, + ROWS or GROUPS) to + the OVER clause. + See for more information + about frame specifications. + + + + When an aggregate function is used as a window function, it aggregates + over the rows within the current row's window frame. + An aggregate used with ORDER BY and the default window frame + definition produces a running sum type of behavior, which may or + may not be what's wanted. To obtain + aggregation over the whole partition, omit ORDER BY or use + ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING. + Other frame specifications can be used to obtain other effects. + + + + + The SQL standard defines a RESPECT NULLS or + IGNORE NULLS option for lead, lag, + first_value, last_value, and + nth_value. This is not implemented in + PostgreSQL: the behavior is always the + same as the standard's default, namely RESPECT NULLS. + Likewise, the standard's FROM FIRST or FROM LAST + option for nth_value is not implemented: only the + default FROM FIRST behavior is supported. (You can achieve + the result of FROM LAST by reversing the ORDER BY + ordering.) + + + + diff --git a/doc/src/sgml/func/func-xml.sgml b/doc/src/sgml/func/func-xml.sgml new file mode 100644 index 00000000000..21f34467a4f --- /dev/null +++ b/doc/src/sgml/func/func-xml.sgml @@ -0,0 +1,1283 @@ + + + XML Functions + + + XML Functions + + + + The functions and function-like expressions described in this + section operate on values of type xml. See for information about the xml + type. The function-like expressions xmlparse + and xmlserialize for converting to and from + type xml are documented there, not in this section. + + + + Use of most of these functions + requires PostgreSQL to have been built + with configure --with-libxml. + + + + Producing XML Content + + + A set of functions and function-like expressions is available for + producing XML content from SQL data. As such, they are + particularly suitable for formatting query results into XML + documents for processing in client applications. + + + + <literal>xmltext</literal> + + + xmltext + + + +xmltext ( text ) xml + + + + The function xmltext returns an XML value with a single + text node containing the input argument as its content. Predefined entities + like ampersand (), left and right angle brackets + (]]>), and quotation marks () + are escaped. + + + + Example: +'); + xmltext +------------------------- + < foo & bar > +]]> + + + + + <literal>xmlcomment</literal> + + + xmlcomment + + + +xmlcomment ( text ) xml + + + + The function xmlcomment creates an XML value + containing an XML comment with the specified text as content. + The text cannot contain -- or end with a + -, otherwise the resulting construct + would not be a valid XML comment. + If the argument is null, the result is null. + + + + Example: + +]]> + + + + + <literal>xmlconcat</literal> + + + xmlconcat + + + +xmlconcat ( xml , ... ) xml + + + + The function xmlconcat concatenates a list + of individual XML values to create a single value containing an + XML content fragment. Null values are omitted; the result is + only null if there are no nonnull arguments. + + + + Example: +', 'foo'); + + xmlconcat +---------------------- + foo +]]> + + + + XML declarations, if present, are combined as follows. If all + argument values have the same XML version declaration, that + version is used in the result, else no version is used. If all + argument values have the standalone declaration value + yes, then that value is used in the result. If + all argument values have a standalone declaration value and at + least one is no, then that is used in the result. + Else the result will have no standalone declaration. If the + result is determined to require a standalone declaration but no + version declaration, a version declaration with version 1.0 will + be used because XML requires an XML declaration to contain a + version declaration. Encoding declarations are ignored and + removed in all cases. + + + + Example: +', ''); + + xmlconcat +----------------------------------- + +]]> + + + + + <literal>xmlelement</literal> + + + xmlelement + + + +xmlelement ( NAME name , XMLATTRIBUTES ( attvalue AS attname , ... ) , content , ... ) xml + + + + The xmlelement expression produces an XML + element with the given name, attributes, and content. + The name + and attname items shown in the syntax are + simple identifiers, not values. The attvalue + and content items are expressions, which can + yield any PostgreSQL data type. The + argument(s) within XMLATTRIBUTES generate attributes + of the XML element; the content value(s) are + concatenated to form its content. + + + + Examples: + + +SELECT xmlelement(name foo, xmlattributes('xyz' as bar)); + + xmlelement +------------------ + + +SELECT xmlelement(name foo, xmlattributes(current_date as bar), 'cont', 'ent'); + + xmlelement +------------------------------------- + content +]]> + + + + Element and attribute names that are not valid XML names are + escaped by replacing the offending characters by the sequence + _xHHHH_, where + HHHH is the character's Unicode + codepoint in hexadecimal notation. For example: + +]]> + + + + An explicit attribute name need not be specified if the attribute + value is a column reference, in which case the column's name will + be used as the attribute name by default. In other cases, the + attribute must be given an explicit name. So this example is + valid: + +CREATE TABLE test (a xml, b xml); +SELECT xmlelement(name test, xmlattributes(a, b)) FROM test; + + But these are not: + +SELECT xmlelement(name test, xmlattributes('constant'), a, b) FROM test; +SELECT xmlelement(name test, xmlattributes(func(a, b))) FROM test; + + + + + Element content, if specified, will be formatted according to + its data type. If the content is itself of type xml, + complex XML documents can be constructed. For example: + +]]> + + Content of other types will be formatted into valid XML character + data. This means in particular that the characters <, >, + and & will be converted to entities. Binary data (data type + bytea) will be represented in base64 or hex + encoding, depending on the setting of the configuration parameter + . The particular behavior for + individual data types is expected to evolve in order to align the + PostgreSQL mappings with those specified in SQL:2006 and later, + as discussed in . + + + + + <literal>xmlforest</literal> + + + xmlforest + + + +xmlforest ( content AS name , ... ) xml + + + + The xmlforest expression produces an XML + forest (sequence) of elements using the given names and content. + As for xmlelement, + each name must be a simple identifier, while + the content expressions can have any data + type. + + + + Examples: + +SELECT xmlforest('abc' AS foo, 123 AS bar); + + xmlforest +------------------------------ + <foo>abc</foo><bar>123</bar> + + +SELECT xmlforest(table_name, column_name) +FROM information_schema.columns +WHERE table_schema = 'pg_catalog'; + + xmlforest +------------------------------------&zwsp;----------------------------------- + <table_name>pg_authid</table_name>&zwsp;<column_name>rolname</column_name> + <table_name>pg_authid</table_name>&zwsp;<column_name>rolsuper</column_name> + ... + + + As seen in the second example, the element name can be omitted if + the content value is a column reference, in which case the column + name is used by default. Otherwise, a name must be specified. + + + + Element names that are not valid XML names are escaped as shown + for xmlelement above. Similarly, content + data is escaped to make valid XML content, unless it is already + of type xml. + + + + Note that XML forests are not valid XML documents if they consist + of more than one element, so it might be useful to wrap + xmlforest expressions in + xmlelement. + + + + + <literal>xmlpi</literal> + + + xmlpi + + + +xmlpi ( NAME name , content ) xml + + + + The xmlpi expression creates an XML + processing instruction. + As for xmlelement, + the name must be a simple identifier, while + the content expression can have any data type. + The content, if present, must not contain the + character sequence ?>. + + + + Example: + +]]> + + + + + <literal>xmlroot</literal> + + + xmlroot + + + +xmlroot ( xml, VERSION {text|NO VALUE} , STANDALONE {YES|NO|NO VALUE} ) xml + + + + The xmlroot expression alters the properties + of the root node of an XML value. If a version is specified, + it replaces the value in the root node's version declaration; if a + standalone setting is specified, it replaces the value in the + root node's standalone declaration. + + + +abc'), + version '1.0', standalone yes); + + xmlroot +---------------------------------------- + + abc +]]> + + + + + <literal>xmlagg</literal> + + + xmlagg + + + +xmlagg ( xml ) xml + + + + The function xmlagg is, unlike the other + functions described here, an aggregate function. It concatenates the + input values to the aggregate function call, + much like xmlconcat does, except that concatenation + occurs across rows rather than across expressions in a single row. + See for additional information + about aggregate functions. + + + + Example: +abc'); +INSERT INTO test VALUES (2, ''); +SELECT xmlagg(x) FROM test; + xmlagg +---------------------- + abc +]]> + + + + To determine the order of the concatenation, an ORDER BY + clause may be added to the aggregate call as described in + . For example: + +abc +]]> + + + + The following non-standard approach used to be recommended + in previous versions, and may still be useful in specific + cases: + +abc +]]> + + + + + + XML Predicates + + + The expressions described in this section check properties + of xml values. + + + + <literal>IS DOCUMENT</literal> + + + IS DOCUMENT + + + +xml IS DOCUMENT boolean + + + + The expression IS DOCUMENT returns true if the + argument XML value is a proper XML document, false if it is not + (that is, it is a content fragment), or null if the argument is + null. See about the difference + between documents and content fragments. + + + + + <literal>IS NOT DOCUMENT</literal> + + + IS NOT DOCUMENT + + + +xml IS NOT DOCUMENT boolean + + + + The expression IS NOT DOCUMENT returns false if the + argument XML value is a proper XML document, true if it is not (that is, + it is a content fragment), or null if the argument is null. + + + + + <literal>XMLEXISTS</literal> + + + XMLEXISTS + + + +XMLEXISTS ( text PASSING BY {REF|VALUE} xml BY {REF|VALUE} ) boolean + + + + The function xmlexists evaluates an XPath 1.0 + expression (the first argument), with the passed XML value as its context + item. The function returns false if the result of that evaluation + yields an empty node-set, true if it yields any other value. The + function returns null if any argument is null. A nonnull value + passed as the context item must be an XML document, not a content + fragment or any non-XML value. + + + + Example: + TorontoOttawa'); + + xmlexists +------------ + t +(1 row) +]]> + + + + The BY REF and BY VALUE clauses + are accepted in PostgreSQL, but are ignored, + as discussed in . + + + + In the SQL standard, the xmlexists function + evaluates an expression in the XML Query language, + but PostgreSQL allows only an XPath 1.0 + expression, as discussed in + . + + + + + <literal>xml_is_well_formed</literal> + + + xml_is_well_formed + + + + xml_is_well_formed_document + + + + xml_is_well_formed_content + + + +xml_is_well_formed ( text ) boolean +xml_is_well_formed_document ( text ) boolean +xml_is_well_formed_content ( text ) boolean + + + + These functions check whether a text string represents + well-formed XML, returning a Boolean result. + xml_is_well_formed_document checks for a well-formed + document, while xml_is_well_formed_content checks + for well-formed content. xml_is_well_formed does + the former if the configuration + parameter is set to DOCUMENT, or the latter if it is set to + CONTENT. This means that + xml_is_well_formed is useful for seeing whether + a simple cast to type xml will succeed, whereas the other two + functions are useful for seeing whether the corresponding variants of + XMLPARSE will succeed. + + + + Examples: + +'); + xml_is_well_formed +-------------------- + f +(1 row) + +SELECT xml_is_well_formed(''); + xml_is_well_formed +-------------------- + t +(1 row) + +SET xmloption TO CONTENT; +SELECT xml_is_well_formed('abc'); + xml_is_well_formed +-------------------- + t +(1 row) + +SELECT xml_is_well_formed_document('bar'); + xml_is_well_formed_document +----------------------------- + t +(1 row) + +SELECT xml_is_well_formed_document('bar'); + xml_is_well_formed_document +----------------------------- + f +(1 row) +]]> + + The last example shows that the checks include whether + namespaces are correctly matched. + + + + + + Processing XML + + + To process values of data type xml, PostgreSQL offers + the functions xpath and + xpath_exists, which evaluate XPath 1.0 + expressions, and the XMLTABLE + table function. + + + + <literal>xpath</literal> + + + XPath + + + +xpath ( xpath text, xml xml , nsarray text[] ) xml[] + + + + The function xpath evaluates the XPath 1.0 + expression xpath (given as text) + against the XML value + xml. It returns an array of XML values + corresponding to the node-set produced by the XPath expression. + If the XPath expression returns a scalar value rather than a node-set, + a single-element array is returned. + + + + The second argument must be a well formed XML document. In particular, + it must have a single root node element. + + + + The optional third argument of the function is an array of namespace + mappings. This array should be a two-dimensional text array with + the length of the second axis being equal to 2 (i.e., it should be an + array of arrays, each of which consists of exactly 2 elements). + The first element of each array entry is the namespace name (alias), the + second the namespace URI. It is not required that aliases provided in + this array be the same as those being used in the XML document itself (in + other words, both in the XML document and in the xpath + function context, aliases are local). + + + + Example: +test', + ARRAY[ARRAY['my', 'http://example.com']]); + + xpath +-------- + {test} +(1 row) +]]> + + + + To deal with default (anonymous) namespaces, do something like this: +test', + ARRAY[ARRAY['mydefns', 'http://example.com']]); + + xpath +-------- + {test} +(1 row) +]]> + + + + + <literal>xpath_exists</literal> + + + xpath_exists + + + +xpath_exists ( xpath text, xml xml , nsarray text[] ) boolean + + + + The function xpath_exists is a specialized form + of the xpath function. Instead of returning the + individual XML values that satisfy the XPath 1.0 expression, this function + returns a Boolean indicating whether the query was satisfied or not + (specifically, whether it produced any value other than an empty node-set). + This function is equivalent to the XMLEXISTS predicate, + except that it also offers support for a namespace mapping argument. + + + + Example: +test', + ARRAY[ARRAY['my', 'http://example.com']]); + + xpath_exists +-------------- + t +(1 row) +]]> + + + + + <literal>xmltable</literal> + + + xmltable + + + + table function + XMLTABLE + + + +XMLTABLE ( + XMLNAMESPACES ( namespace_uri AS namespace_name , ... ), + row_expression PASSING BY {REF|VALUE} document_expression BY {REF|VALUE} + COLUMNS name { type PATH column_expression DEFAULT default_expression NOT NULL | NULL + | FOR ORDINALITY } + , ... +) setof record + + + + The xmltable expression produces a table based + on an XML value, an XPath filter to extract rows, and a + set of column definitions. + Although it syntactically resembles a function, it can only appear + as a table in a query's FROM clause. + + + + The optional XMLNAMESPACES clause gives a + comma-separated list of namespace definitions, where + each namespace_uri is a text + expression and each namespace_name is a simple + identifier. It specifies the XML namespaces used in the document and + their aliases. A default namespace specification is not currently + supported. + + + + The required row_expression argument is an + XPath 1.0 expression (given as text) that is evaluated, + passing the XML value document_expression as + its context item, to obtain a set of XML nodes. These nodes are what + xmltable transforms into output rows. No rows + will be produced if the document_expression + is null, nor if the row_expression produces + an empty node-set or any value other than a node-set. + + + + document_expression provides the context + item for the row_expression. It must be a + well-formed XML document; fragments/forests are not accepted. + The BY REF and BY VALUE clauses + are accepted but ignored, as discussed in + . + + + + In the SQL standard, the xmltable function + evaluates expressions in the XML Query language, + but PostgreSQL allows only XPath 1.0 + expressions, as discussed in + . + + + + The required COLUMNS clause specifies the + column(s) that will be produced in the output table. + See the syntax summary above for the format. + A name is required for each column, as is a data type + (unless FOR ORDINALITY is specified, in which case + type integer is implicit). The path, default and + nullability clauses are optional. + + + + A column marked FOR ORDINALITY will be populated + with row numbers, starting with 1, in the order of nodes retrieved from + the row_expression's result node-set. + At most one column may be marked FOR ORDINALITY. + + + + + XPath 1.0 does not specify an order for nodes in a node-set, so code + that relies on a particular order of the results will be + implementation-dependent. Details can be found in + . + + + + + The column_expression for a column is an + XPath 1.0 expression that is evaluated for each row, with the current + node from the row_expression result as its + context item, to find the value of the column. If + no column_expression is given, then the + column name is used as an implicit path. + + + + If a column's XPath expression returns a non-XML value (which is limited + to string, boolean, or double in XPath 1.0) and the column has a + PostgreSQL type other than xml, the column will be set + as if by assigning the value's string representation to the PostgreSQL + type. (If the value is a boolean, its string representation is taken + to be 1 or 0 if the output + column's type category is numeric, otherwise true or + false.) + + + + If a column's XPath expression returns a non-empty set of XML nodes + and the column's PostgreSQL type is xml, the column will + be assigned the expression result exactly, if it is of document or + content form. + + + A result containing more than one element node at the top level, or + non-whitespace text outside of an element, is an example of content form. + An XPath result can be of neither form, for example if it returns an + attribute node selected from the element that contains it. Such a result + will be put into content form with each such disallowed node replaced by + its string value, as defined for the XPath 1.0 + string function. + + + + + + A non-XML result assigned to an xml output column produces + content, a single text node with the string value of the result. + An XML result assigned to a column of any other type may not have more than + one node, or an error is raised. If there is exactly one node, the column + will be set as if by assigning the node's string + value (as defined for the XPath 1.0 string function) + to the PostgreSQL type. + + + + The string value of an XML element is the concatenation, in document order, + of all text nodes contained in that element and its descendants. The string + value of an element with no descendant text nodes is an + empty string (not NULL). + Any xsi:nil attributes are ignored. + Note that the whitespace-only text() node between two non-text + elements is preserved, and that leading whitespace on a text() + node is not flattened. + The XPath 1.0 string function may be consulted for the + rules defining the string value of other XML node types and non-XML values. + + + + The conversion rules presented here are not exactly those of the SQL + standard, as discussed in . + + + + If the path expression returns an empty node-set + (typically, when it does not match) + for a given row, the column will be set to NULL, unless + a default_expression is specified; then the + value resulting from evaluating that expression is used. + + + + A default_expression, rather than being + evaluated immediately when xmltable is called, + is evaluated each time a default is needed for the column. + If the expression qualifies as stable or immutable, the repeat + evaluation may be skipped. + This means that you can usefully use volatile functions like + nextval in + default_expression. + + + + Columns may be marked NOT NULL. If the + column_expression for a NOT + NULL column does not match anything and there is + no DEFAULT or + the default_expression also evaluates to null, + an error is reported. + + + + Examples: + + + AU + Australia + + + JP + Japan + Shinzo Abe + 145935 + + + SG + Singapore + 697 + + +$$ AS data; + +SELECT xmltable.* + FROM xmldata, + XMLTABLE('//ROWS/ROW' + PASSING data + COLUMNS id int PATH '@id', + ordinality FOR ORDINALITY, + "COUNTRY_NAME" text, + country_id text PATH 'COUNTRY_ID', + size_sq_km float PATH 'SIZE[@unit = "sq_km"]', + size_other text PATH + 'concat(SIZE[@unit!="sq_km"], " ", SIZE[@unit!="sq_km"]/@unit)', + premier_name text PATH 'PREMIER_NAME' DEFAULT 'not specified'); + + id | ordinality | COUNTRY_NAME | country_id | size_sq_km | size_other | premier_name +----+------------+--------------+------------+------------+--------------+--------------- + 1 | 1 | Australia | AU | | | not specified + 5 | 2 | Japan | JP | | 145935 sq_mi | Shinzo Abe + 6 | 3 | Singapore | SG | 697 | | not specified +]]> + + The following example shows concatenation of multiple text() nodes, + usage of the column name as XPath filter, and the treatment of whitespace, + XML comments and processing instructions: + + + Hello2a2 bbbxxxCC + +$$ AS data; + +SELECT xmltable.* + FROM xmlelements, XMLTABLE('/root' PASSING data COLUMNS element text); + element +------------------------- + Hello2a2 bbbxxxCC +]]> + + + + The following example illustrates how + the XMLNAMESPACES clause can be used to specify + a list of namespaces + used in the XML document as well as in the XPath expressions: + + + + + +'::xml) +) +SELECT xmltable.* + FROM XMLTABLE(XMLNAMESPACES('http://example.com/myns' AS x, + 'http://example.com/b' AS "B"), + '/x:example/x:item' + PASSING (SELECT data FROM xmldata) + COLUMNS foo int PATH '@foo', + bar int PATH '@B:bar'); + foo | bar +-----+----- + 1 | 2 + 3 | 4 + 4 | 5 +(3 rows) +]]> + + + + + + Mapping Tables to XML + + + XML export + + + + The following functions map the contents of relational tables to + XML values. They can be thought of as XML export functionality: + +table_to_xml ( table regclass, nulls boolean, + tableforest boolean, targetns text ) xml +query_to_xml ( query text, nulls boolean, + tableforest boolean, targetns text ) xml +cursor_to_xml ( cursor refcursor, count integer, nulls boolean, + tableforest boolean, targetns text ) xml + + + + + table_to_xml maps the content of the named + table, passed as parameter table. The + regclass type accepts strings identifying tables using the + usual notation, including optional schema qualification and + double quotes (see for details). + query_to_xml executes the + query whose text is passed as parameter + query and maps the result set. + cursor_to_xml fetches the indicated number of + rows from the cursor specified by the parameter + cursor. This variant is recommended if + large tables have to be mapped, because the result value is built + up in memory by each function. + + + + If tableforest is false, then the resulting + XML document looks like this: + + + data + data + + + + ... + + + ... + +]]> + + If tableforest is true, the result is an + XML content fragment that looks like this: + + data + data + + + + ... + + +... +]]> + + If no table name is available, that is, when mapping a query or a + cursor, the string table is used in the first + format, row in the second format. + + + + The choice between these formats is up to the user. The first + format is a proper XML document, which will be important in many + applications. The second format tends to be more useful in the + cursor_to_xml function if the result values are to be + reassembled into one document later on. The functions for + producing XML content discussed above, in particular + xmlelement, can be used to alter the results + to taste. + + + + The data values are mapped in the same way as described for the + function xmlelement above. + + + + The parameter nulls determines whether null + values should be included in the output. If true, null values in + columns are represented as: + +]]> + where xsi is the XML namespace prefix for XML + Schema Instance. An appropriate namespace declaration will be + added to the result value. If false, columns containing null + values are simply omitted from the output. + + + + The parameter targetns specifies the + desired XML namespace of the result. If no particular namespace + is wanted, an empty string should be passed. + + + + The following functions return XML Schema documents describing the + mappings performed by the corresponding functions above: + +table_to_xmlschema ( table regclass, nulls boolean, + tableforest boolean, targetns text ) xml +query_to_xmlschema ( query text, nulls boolean, + tableforest boolean, targetns text ) xml +cursor_to_xmlschema ( cursor refcursor, nulls boolean, + tableforest boolean, targetns text ) xml + + It is essential that the same parameters are passed in order to + obtain matching XML data mappings and XML Schema documents. + + + + The following functions produce XML data mappings and the + corresponding XML Schema in one document (or forest), linked + together. They can be useful where self-contained and + self-describing results are wanted: + +table_to_xml_and_xmlschema ( table regclass, nulls boolean, + tableforest boolean, targetns text ) xml +query_to_xml_and_xmlschema ( query text, nulls boolean, + tableforest boolean, targetns text ) xml + + + + + In addition, the following functions are available to produce + analogous mappings of entire schemas or the entire current + database: + +schema_to_xml ( schema name, nulls boolean, + tableforest boolean, targetns text ) xml +schema_to_xmlschema ( schema name, nulls boolean, + tableforest boolean, targetns text ) xml +schema_to_xml_and_xmlschema ( schema name, nulls boolean, + tableforest boolean, targetns text ) xml + +database_to_xml ( nulls boolean, + tableforest boolean, targetns text ) xml +database_to_xmlschema ( nulls boolean, + tableforest boolean, targetns text ) xml +database_to_xml_and_xmlschema ( nulls boolean, + tableforest boolean, targetns text ) xml + + + These functions ignore tables that are not readable by the current user. + The database-wide functions additionally ignore schemas that the current + user does not have USAGE (lookup) privilege for. + + + + Note that these potentially produce a lot of data, which needs to + be built up in memory. When requesting content mappings of large + schemas or databases, it might be worthwhile to consider mapping the + tables separately instead, possibly even through a cursor. + + + + The result of a schema content mapping looks like this: + + + +table1-mapping + +table2-mapping + +... + +]]> + + where the format of a table mapping depends on the + tableforest parameter as explained above. + + + + The result of a database content mapping looks like this: + + + + + ... + + + + ... + + +... + +]]> + + where the schema mapping is as above. + + + + As an example of using the output produced by these functions, + shows an XSLT stylesheet that + converts the output of + table_to_xml_and_xmlschema to an HTML + document containing a tabular rendition of the table data. In a + similar manner, the results from these functions can be + converted into other XML-based formats. + + + + XSLT Stylesheet for Converting SQL/XML Output to HTML + + + + + + + + + + + + + <xsl:value-of select="name(current())"/> + + + + + + + + + + + + + + + + +

+ + + + + +]]> + + + diff --git a/doc/src/sgml/func/func.sgml b/doc/src/sgml/func/func.sgml new file mode 100644 index 00000000000..f351ef53f63 --- /dev/null +++ b/doc/src/sgml/func/func.sgml @@ -0,0 +1,84 @@ + + + + Functions and Operators + + + function + + + + operator + + + + PostgreSQL provides a large number of + functions and operators for the built-in data types. This chapter + describes most of them, although additional special-purpose functions + appear in relevant sections of the manual. Users can also + define their own functions and operators, as described in + . The + psql commands \df and + \do can be used to list all + available functions and operators, respectively. + + + + The notation used throughout this chapter to describe the argument and + result data types of a function or operator is like this: + +repeat ( text, integer ) text + + which says that the function repeat takes one text and + one integer argument and returns a result of type text. The right arrow + is also used to indicate the result of an example, thus: + +repeat('Pg', 4) PgPgPgPg + + + + + If you are concerned about portability then note that most of + the functions and operators described in this chapter, with the + exception of the most trivial arithmetic and comparison operators + and some explicitly marked functions, are not specified by the + SQL standard. Some of this extended functionality + is present in other SQL database management + systems, and in many cases this functionality is compatible and + consistent between the various implementations. + + + +&func-logical; +&func-comparison; +&func-math; +&func-string; +&func-binarystring; +&func-bitstring; +&func-matching; +&func-formatting; +&func-datetime; +&func-enum; +&func-geometry; +&func-net; +&func-textsearch; +&func-uuid; +&func-xml; +&func-json; +&func-sequence; +&func-conditional; +&func-array; +&func-range; +&func-aggregate; +&func-window; +&func-merge-support; +&func-subquery; +&func-comparisons; +&func-srf; +&func-info; +&func-admin; +&func-trigger; +&func-event-triggers; +&func-statistics; + +