-C Improvements\sto\sthe\saccurancy\sof\sthe\sfuzzinvariants.c\stesting\smodule\swhen\nSQLITE_ALLOW_ROWID_IN_VIEW\sis\sdefined\sand\sthe\stest\squery\sinvolves\srowids.
-D 2024-04-06T17:37:30.138
+C Add\scomments\sto\snote\sthe\sname\sabiguity\sbetween\sthe\sMySQL\spush-down\noptimization\sand\sthe\sWHERE-clause\spush-down\soptimization.
+D 2024-04-07T10:27:18.165
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F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
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U drh
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# Remove this line to create a well-formed Fossil manifest.
-c6e873d4db3ef36a0d561e64ead6feada5d1654c0757b4b6e55f671c9db66469
\ No newline at end of file
+3d5fb1ec7a0440072d6e3b957903c85d0f32b8b07207a1ef22d1a69cf5e664d1
\ No newline at end of file
if( !ExprHasProperty(pExpr, EP_Collate) ){
/* A TK_COLLATE Expr node without the EP_Collate tag is a so-called
** "SOFT-COLLATE" that is added to constraints that are pushed down
- ** from outer queries into sub-queries by the push-down optimization.
- ** Clear subtypes as subtypes may not cross a subquery boundary.
+ ** from outer queries into sub-queries by the WHERE-clause push-down
+ ** optimization. Clear subtypes as subtypes may not cross a subquery
+ ** boundary.
*/
assert( pExpr->pLeft );
sqlite3ExprCode(pParse, pExpr->pLeft, target);
** The hope is that the terms added to the inner query will make it more
** efficient.
**
+** NAME AMBIGUITY
+**
+** This optimization is called the "WHERE-clause push-down optimization".
+**
+** Do not confuse this optimization with another unrelated optimization
+** with a similar name: The "MySQL push-down optimization" causes WHERE
+** clause terms that can be evaluated using only the index and without
+** reference to the table are run first, so that if they are false,
+** unnecessary table seeks are avoided.
+**
+** RULES
+**
** Do not attempt this optimization if:
**
** (1) (** This restriction was removed on 2017-09-29. We used to
** (9c) There is a RIGHT JOIN (or FULL JOIN) in between the ON/USING
** clause and the subquery.
**
-** Without this restriction, the push-down optimization might move
-** the ON/USING filter expression from the left side of a RIGHT JOIN
-** over to the right side, which leads to incorrect answers. See
-** also restriction (6) in sqlite3ExprIsSingleTableConstraint().
+** Without this restriction, the WHERE-clause push-down optimization
+** might move the ON/USING filter expression from the left side of a
+** RIGHT JOIN over to the right side, which leads to incorrect answers.
+** See also restriction (6) in sqlite3ExprIsSingleTableConstraint().
**
** (10) The inner query is not the right-hand table of a RIGHT JOIN.
**
#endif
assert( pItem->pSelect && (pItem->pSelect->selFlags & SF_PushDown)!=0 );
}else{
- TREETRACE(0x4000,pParse,p,("Push-down not possible\n"));
+ TREETRACE(0x4000,pParse,p,("WHERE-lcause push-down not possible\n"));
}
/* Convert unused result columns of the subquery into simple NULL
#define SQLITE_CursorHints 0x00000400 /* Add OP_CursorHint opcodes */
#define SQLITE_Stat4 0x00000800 /* Use STAT4 data */
/* TH3 expects this value ^^^^^^^^^^ to be 0x0000800. Don't change it */
-#define SQLITE_PushDown 0x00001000 /* The push-down optimization */
+#define SQLITE_PushDown 0x00001000 /* WHERE-clause push-down opt */
#define SQLITE_SimplifyJoin 0x00002000 /* Convert LEFT JOIN to JOIN */
#define SQLITE_SkipScan 0x00004000 /* Skip-scans */
#define SQLITE_PropagateConst 0x00008000 /* The constant propagation opt */
#define SF_View 0x0200000 /* SELECT statement is a view */
#define SF_NoopOrderBy 0x0400000 /* ORDER BY is ignored for this query */
#define SF_UFSrcCheck 0x0800000 /* Check pSrc as required by UPDATE...FROM */
-#define SF_PushDown 0x1000000 /* SELECT has be modified by push-down opt */
+#define SF_PushDown 0x1000000 /* Modified by WHERE-clause push-down opt */
#define SF_MultiPart 0x2000000 /* Has multiple incompatible PARTITIONs */
#define SF_CopyCte 0x4000000 /* SELECT statement is a copy of a CTE */
#define SF_OrderByReqd 0x8000000 /* The ORDER BY clause may not be omitted */
** iLoop==3: Code all remaining expressions.
**
** An effort is made to skip unnecessary iterations of the loop.
+ **
+ ** This optimization of causing simple query restrictions to occur before
+ ** more complex one is call the "push-down" optimization in MySQL. Here
+ ** in SQLite, the name is "MySQL push-down", since there is also another
+ ** totally unrelated optimization called "WHERE-clause push-down".
+ ** Sometimes the qualifier is omitted, resulting in an ambiguity, so beware.
*/
iLoop = (pIdx ? 1 : 2);
do{
-# 2017 April 29
+# 2017-04-29
#
# The author disclaims copyright to this source code. In place of
# a legal notice, here is a blessing:
# May you share freely, never taking more than you give.
#
#***********************************************************************
+#
+# Test cases for the push-down optimizations.
+#
+#
+# There are two different meanings for "push-down optimization".
+#
+# (1) "MySQL push-down" means that WHERE clause terms that can be
+# evaluated using only the index and without reference to the
+# table are run first, so that if they are false, unnecessary table
+# seeks are avoided. See https://sqlite.org/src/info/d7bb79ed3a40419d
+# from 2017-04-29.
+#
+# (2) "WHERE-clause pushdown" means to push WHERE clause terms in
+# outer queries down into subqueries. See
+# https://sqlite.org/src/info/6df18e949d367629 from 2015-06-02.
+#
+# This module started out as tests for MySQL push-down only. But because
+# of naming ambiguity, it has picked up test cases for WHERE-clause push-down
+# over the years.
+#
set testdir [file dirname $argv0]
source $testdir/tester.tcl
} {three}
# 2022-11-25 dbsqlfuzz crash-3a548de406a50e896c1bf7142692d35d339d697f
-# Disable the push-down optimization for compound subqueries if any
-# arm of the compound has an incompatible affinity.
+# Disable the WHERE-clause push-down optimization for compound subqueries
+# if any arm of the compound has an incompatible affinity.
#
reset_db
do_execsql_test 3.1 {
# SELECT (SELECT count(*) FROM t1)+(SELECT count(*) FROM t2)
# 2023-05-09 https://sqlite.org/forum/forumpost/a7d4be7fb6
-# Restriction (9) on the push-down optimization.
+# Restriction (9) on the WHERE-clause push-down optimization.
#
reset_db
db null -
projects / thirdparty / sqlite.git / commitdiff
