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Diffstat (limited to 'doc/src/sgml/func.sgml')
| -rw-r--r-- | doc/src/sgml/func.sgml | 48 |
1 files changed, 33 insertions, 15 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index baeef816181..a3e66eabc34 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.137 2003/02/05 17:41:32 tgl Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.138 2003/02/06 20:25:31 tgl Exp $ PostgreSQL documentation --> @@ -2665,10 +2665,24 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> due to their availability in programming languages such as Perl and Tcl. <acronym>RE</acronym>s using these non-POSIX extensions are called <firstterm>advanced</> <acronym>RE</acronym>s or <acronym>ARE</>s - in this documentation. We first describe the ERE/ARE flavor and then - mention the restrictions of the BRE form. + 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. </para> + <note> + <para> + The form of regular expressions accepted by <productname>PostgreSQL</> + can be chosen by setting the <varname>REGEX_FLAVOR</> run-time parameter + (described in the &cite-admin;). The usual setting is + <literal>advanced</>, but one might choose <literal>extended</> for + maximum backwards compatibility with pre-7.4 releases of + <productname>PostgreSQL</>. + </para> + </note> + <para> A regular expression is defined as one or more <firstterm>branches</firstterm>, separated by @@ -2784,7 +2798,7 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> meaning in <productname>PostgreSQL</> string literals. To write a pattern constant that contains a backslash, you must write two backslashes in the query. - </para> + </para> </note> <table id="posix-quantifiers-table"> @@ -3392,11 +3406,11 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> </para> <para> - Normally the flavor of RE being used is specified by - application-dependent means. - However, this can be overridden by a <firstterm>director</>. + Normally the flavor of RE being used is determined by + <varname>REGEX_FLAVOR</>. + However, this can be overridden by a <firstterm>director</> prefix. If an RE of any flavor begins with <literal>***:</>, - the rest of the RE is an ARE. + the rest of the RE is taken as an ARE. If an RE of any flavor begins with <literal>***=</>, the rest of the RE is taken to be a literal string, with all characters considered ordinary characters. @@ -3407,8 +3421,8 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> a sequence <literal>(?</><replaceable>xyz</><literal>)</> (where <replaceable>xyz</> is one or more alphabetic characters) specifies options affecting the rest of the RE. - These supplement, and can override, - any options specified externally. + These options override any previously determined options (including + both the RE flavor and case sensitivity). The available option letters are shown in <xref linkend="posix-embedded-options-table">. </para> @@ -3432,7 +3446,7 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> <row> <entry> <literal>c</> </entry> - <entry> case-sensitive matching (usual default) </entry> + <entry> case-sensitive matching (overrides operator type) </entry> </row> <row> @@ -3443,7 +3457,7 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> <row> <entry> <literal>i</> </entry> <entry> case-insensitive matching (see - <xref linkend="posix-matching-rules">) </entry> + <xref linkend="posix-matching-rules">) (overrides operator type) </entry> </row> <row> @@ -3471,12 +3485,12 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> <row> <entry> <literal>s</> </entry> - <entry> non-newline-sensitive matching (usual default) </entry> + <entry> non-newline-sensitive matching (default) </entry> </row> <row> <entry> <literal>t</> </entry> - <entry> tight syntax (usual default; see below) </entry> + <entry> tight syntax (default; see below) </entry> </row> <row> @@ -3696,7 +3710,7 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> </para> <para> - Two significant incompatibilites exist between AREs and the ERE syntax + Two significant incompatibilities exist between AREs and the ERE syntax recognized by pre-7.4 releases of <productname>PostgreSQL</>: <itemizedlist> @@ -3717,6 +3731,10 @@ SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation> </para> </listitem> </itemizedlist> + + While these differences are unlikely to create a problem for most + applications, you can avoid them if necessary by + setting <varname>REGEX_FLAVOR</> to <literal>extended</>. </para> </sect3> |