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Document that the regexp split functions ignore zero-length matches in

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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.
This commit is contained in:
Tom Lane 2007-08-13 01:18:47 +00:00
parent b70d4a62ee
commit a44af6df85
1 changed files with 14 additions and 5 deletions
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19
doc/src/sgml/func.sgml
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@ -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: