regex_replace() to 8.1.X.
<!--
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+$PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.291.2.6 2006/05/30 12:32:37 momjian Exp $
PostgreSQL documentation
-->
<entry><literal><function>substring</function>(<parameter>string</parameter> from <replaceable>pattern</replaceable>)</literal></entry>
<entry><type>text</type></entry>
<entry>
- Extract substring matching POSIX regular expression
+ Extract substring matching POSIX regular expression. See
+ <xref linkend="functions-matching"> for more information on pattern
+ matching.
</entry>
<entry><literal>substring('Thomas' from '...$')</literal></entry>
<entry><literal>mas</literal></entry>
<entry><literal><function>substring</function>(<parameter>string</parameter> from <replaceable>pattern</replaceable> for <replaceable>escape</replaceable>)</literal></entry>
<entry><type>text</type></entry>
<entry>
- Extract substring matching <acronym>SQL</acronym> regular
- expression
+ Extract substring matching <acronym>SQL</acronym> regular expression.
+ See <xref linkend="functions-matching"> for more information on
+ pattern matching.
</entry>
<entry><literal>substring('Thomas' from '%#"o_a#"_' for '#')</literal></entry>
<entry><literal>oma</literal></entry>
<entry><literal>'O''Reilly'</literal></entry>
</row>
+ <row>
+ <entry><literal><function>regexp_replace</function>(<parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>, <parameter>replacement</parameter> <type>text</type> [,<parameter>flags</parameter> <type>text</type>])</literal></entry>
+ <entry><type>text</type></entry>
+ <entry>
+ Replace substring matching POSIX regular expression. See
+ <xref linkend="functions-matching"> for more information on pattern
+ matching.
+ </entry>
+ <entry><literal>regexp_replace('Thomas', '.[mN]a.', 'M')</literal></entry>
+ <entry><literal>ThM</literal></entry>
+ </row>
+
<row>
<entry><literal><function>repeat</function>(<parameter>string</parameter> <type>text</type>, <parameter>number</parameter> <type>int</type>)</literal></entry>
<entry><type>text</type></entry>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.49 2005/11/04 23:14:00 petere Exp $
+$PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.49.2.1 2006/05/30 12:32:37 momjian Exp $
-->
<chapter id="plperl">
<ulink url="http://www.perl.com">Perl programming language</ulink>.
</para>
+ <para> The usual advantage to using PL/Perl is that this allows use,
+ within stored functions, of the manyfold <quote>string
+ munging</quote> operators and functions available for Perl. Parsing
+ complex strings may be be easier using Perl than it is with the
+ string functions and control structures provided in PL/pgsql.</para>
+
<para>
To install PL/Perl in a particular database, use
<literal>createlang plperl <replaceable>dbname</></literal>.
<!--
-$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.80.2.4 2006/02/05 02:48:20 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.80.2.5 2006/05/30 12:32:37 momjian Exp $
-->
<chapter id="plpgsql">
<para>
That means that your client application must send each query to
- the database server, wait for it to be processed, receive the
- results, do some computation, then send other queries to the
- server. All this incurs interprocess communication and may also
- incur network overhead if your client is on a different machine
- than the database server.
+ the database server, wait for it to be processed, receive and
+ process the results, do some computation, then send further
+ queries to the server. All this incurs interprocess
+ communication and will also incur network overhead if your client
+ is on a different machine than the database server.
</para>
<para>
- With <application>PL/pgSQL</application> you can group a block of computation and a
- series of queries <emphasis>inside</emphasis> the
- database server, thus having the power of a procedural
- language and the ease of use of SQL, but saving lots of
- time because you don't have the whole client/server
- communication overhead. This can make for a
- considerable performance increase.
+ With <application>PL/pgSQL</application> you can group a block of
+ computation and a series of queries <emphasis>inside</emphasis>
+ the database server, thus having the power of a procedural
+ language and the ease of use of SQL, but with considerable
+ savings because you don't have the whole client/server
+ communication overhead.
+ </para>
+ <itemizedlist>
+
+ <listitem><para> Elimination of additional round trips between
+ client and server </para></listitem>
+
+ <listitem><para> Intermediate results that the client does not
+ need do not need to be marshalled or transferred between server
+ and client </para></listitem>
+
+ <listitem><para> There is no need for additional rounds of query
+ parsing </para></listitem>
+
+ </itemizedlist>
+ <para> This can allow for a considerable performance increase as
+ compared to an application that does not use stored functions.
</para>
<para>
<!--
-$PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.38 2005/05/20 01:52:25 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.38.2.1 2006/05/30 12:32:37 momjian Exp $
-->
<chapter id="pltcl">
<title>Overview</title>
<para>
- PL/Tcl offers most of the capabilities a function
- writer has in the C language, except for some restrictions.
+ PL/Tcl offers most of the capabilities a function writer has in
+ the C language, with a few restrictions, and with the addition of
+ the powerful string processing libraries that are available for
+ Tcl.
</para>
<para>
- The good restriction is that everything is executed in a safe
- Tcl interpreter. In addition to the limited command set of safe Tcl, only
- a few commands are available to access the database via SPI and to raise
- messages via <function>elog()</>. There is no way to access internals of the
- database server or to gain OS-level access under the permissions of the
- <productname>PostgreSQL</productname> server process, as a C function can do.
- Thus, any unprivileged database user may be
- permitted to use this language.
+ One compelling <emphasis>good</emphasis> restriction is that
+ everything is executed from within the safety of the context of a
+ Tcl interpreter. In addition to the limited command set of safe
+ Tcl, only a few commands are available to access the database via
+ SPI and to raise messages via <function>elog()</>. PL/Tcl
+ provides no way to access internals of the database server or to
+ gain OS-level access under the permissions of the
+ <productname>PostgreSQL</productname> server process, as a C
+ function can do. Thus, unprivileged database users may be trusted
+ to use this language; it does not give them unlimited authority.
</para>
<para>
- The other, implementation restriction is that Tcl functions cannot
- be used to create input/output functions for new data types.
+ The other notable implementation restriction is that Tcl functions
+ may not be used to create input/output functions for new data
+ types.
</para>
<para>
Sometimes it is desirable to write Tcl functions that are not restricted
a user logged in as the database administrator.
</para>
<para>
- The shared object for the <application>PL/Tcl</> and <application>PL/TclU</> call handlers is
- automatically built and installed in the
- <productname>PostgreSQL</productname>
- library directory if Tcl support is specified
- in the configuration step of the installation procedure. To install
-
<application>PL/Tcl</> and/or <application>PL/TclU</> in a particular database, use the
+ The shared object code for the <application>PL/Tcl</> and
+ <application>PL/TclU</> call handlers is automatically built and
+ installed in the <productname>PostgreSQL</productname> library
+ directory if Tcl support is specified in the configuration step of
+ the installation procedure. To install <application>PL/Tcl</>
+ and/or <application>PL/TclU</> in a particular database, use the
<command>createlang</command> program, for example
<literal>createlang pltcl <replaceable>dbname</></literal> or
<literal>createlang pltclu <replaceable>dbname</></literal>.
projects / thirdparty / postgresql.git / commitdiff
