From a44af6df859f38247317d1714c2d941961e42919 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 13 Aug 2007 01:18:47 +0000
Subject: [PATCH] Document that the regexp split functions ignore zero-length
matches in certain corner cases. Per discussion, the code does what we want,
but it really needs to be documented that these functions act differently
from regexp_matches.
---
doc/src/sgml/func.sgml | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 4e5f8f1148a..52858efc600 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.384 2007/08/11 03:56:24 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.385 2007/08/13 01:18:47 tgl Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@@ -3383,10 +3383,12 @@ SELECT foo FROM regexp_split_to_table('the quick brown fox', E'\\s*') AS foo;
</para>
<para>
- <productname>PostgreSQL</productname>'s regular expressions are implemented
- using a package written by Henry Spencer. Much of
- the description of regular expressions below is copied verbatim from his
- manual entry.
+ 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
+ <function>regexp_matches</>, but is usually the most convenient behavior
+ in practice. Other software systems such as Perl use similar definitions.
</para>
<!-- derived from the re_syntax.n man page -->
@@ -3394,6 +3396,13 @@ SELECT foo FROM regexp_split_to_table('the quick brown fox', E'\\s*') AS foo;
<sect3 id="posix-syntax-details">
<title>Regular Expression Details</title>
+ <para>
+ <productname>PostgreSQL</productname>'s regular expressions are implemented
+ using a package written by Henry Spencer. Much of
+ the description of regular expressions below is copied verbatim from his
+ manual entry.
+ </para>
+
<para>
Regular expressions (<acronym>RE</acronym>s), as defined in
<acronym>POSIX</acronym> 1003.2, come in two forms:
--
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