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Improve similar_escape() in two different ways:

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* Stop escaping ? and {.  As of SQL:2008, SIMILAR TO is defined to have
POSIX-compatible interpretation of ? as well as {m,n} and related constructs,
so we should allow these things through to our regex engine.

* Escape ^ and $.  It appears that our regex engine will treat ^^ at the
beginning of the string the same as ^, and similarly for $$ at the end of
the string, which meant that SIMILAR TO was effectively ignoring ^ at the
start of the pattern and $ at the end.  Since these are not supposed to be
metacharacters, this is a bug.

The second part of this is arguably a back-patchable bug fix, but I'm
hesitant to do that because it might break applications that are expecting
something like "col SIMILAR TO '^foo$'" to work like a POSIX pattern.
Seems safer to only change it at a major version boundary.

Per discussion of an example from Doug Gorley.
This commit is contained in:
Tom Lane 2009-10-10 03:50:15 +00:00
parent 8a5849b7ff
commit 05d249717d
2 changed files with 32 additions and 8 deletions
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32
doc/src/sgml/func.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.488 2009/10/09 21:02:55 petere Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.489 2009/10/10 03:50:15 tgl Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
@ -3154,6 +3154,31 @@ cast(-44 as bit(12)) <lineannotation>111111010100</lineannotation>
or more times.
</para>
</listitem>
<listitem>
<para>
<literal>?</literal> denotes repetition of the previous item zero
or one time.
</para>
</listitem>
<listitem>
<para>
<literal>{</><replaceable>m</><literal>}</literal> denotes repetition
of the previous item exactly <replaceable>m</> times.
</para>
</listitem>
<listitem>
<para>
<literal>{</><replaceable>m</><literal>,}</literal> denotes repetition
of the previous item <replaceable>m</> or more times.
</para>
</listitem>
<listitem>
<para>
<literal>{</><replaceable>m</><literal>,</><replaceable>n</><literal>}</>
denotes repetition of the previous item at least <replaceable>m</> and
not more than <replaceable>n</> times.
</para>
</listitem>
<listitem>
<para>
Parentheses <literal>()</literal> can be used to group items into
@ -3168,9 +3193,8 @@ cast(-44 as bit(12)) <lineannotation>111111010100</lineannotation>
</listitem>
</itemizedlist>
Notice that bounded repetition operators (<literal>?</> and
<literal>{...}</>) are not provided, though they exist in POSIX.
Also, the period (<literal>.</>) is not a metacharacter.
Notice that the period (<literal>.</>) is not a metacharacter
for <function>SIMILAR TO</>.
</para>
<para>

8
src/backend/utils/adt/regexp.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.82 2009/06/11 14:49:04 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.83 2009/10/10 03:50:15 tgl Exp $
*
* Alistair Crooks added the code for the regex caching
* agc - cached the regular expressions used - there's a good chance
@ -639,7 +639,7 @@ textregexreplace(PG_FUNCTION_ARGS)
/*
* similar_escape()
* Convert a SQL99 regexp pattern to POSIX style, so it can be used by
* Convert a SQL:2008 regexp pattern to POSIX style, so it can be used by
* our regexp engine.
*/
Datum
@ -740,8 +740,8 @@ similar_escape(PG_FUNCTION_ARGS)
}
else if (pchar == '_')
*r++ = '.';
else if (pchar == '\\' || pchar == '.' || pchar == '?' ||
pchar == '{')
else if (pchar == '\\' || pchar == '.' ||
pchar == '^' || pchar == '$')
{
*r++ = '\\';
*r++ = pchar;