Feedback-ID: i0fe9450f:Fastmail
Date: Fri, 23 May 2025 10:10:04 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: SIMILAR TO expressions translate wildcards where they shouldn't
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References: <16ab039d1af455652bdf4173402ddda145f2c73b.camel@cybertec.at>
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On Thu, May 22, 2025 at 11:18:44PM +0200, Laurenz Albe wrote:
> The underscore before the [:alpha:] is left alone, but the one after
> it gets translated to a period.  Now the underscore is a wildcard
> that corresponds to the period in regular expressions, but characters
> in square brackets should lose their special meaning.  The code in
> utils/adt/regexp.c doesn't expect that square brackets can be nested.
>=20
> The attached patch fixes the bug.

Oh, good catch.  [_[:alpha:]] and [[:alpha:]_] both that this should
match every string made of a-zA-Z and underscores, but this is failing
to do the job for the latter.

+           if (pchar !=3D '^' && charclass_start)
+               charclass_start =3D false;

I'm a bit puzzled by this part about '^', though, resetting the fact
that we are in a squared bracket section with '^' treated as an
exception.  Perhaps this deserves a comment?
--
Michael

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