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From: Nitin Motiani <nitinmotiani@google.com>
Date: Sat, 6 Jun 2026 17:55:20 +0530
Message-ID: 
 <CAH5HC94r6aRJAVOqUiO=eAt3hvBA3r=H77y8qd3cV2pzOskQUA@mail.gmail.com>
Subject: Re: [PATCH] Fix for bug #19474: LIKE fails to match literal
 backslashes with nondeterministic collations
To: Ewan Young <kdbase.hack@gmail.com>
Cc: Zsolt Parragi <zsolt.parragi@percona.com>,
 pgsql-hackers@lists.postgresql.org
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> I reviewed the v2 patch.
>

Thanks for the feedback.

>
> 1. The commit message describes the symptom as "an incorrect match
> failure", but the bug also causes incorrect matches in the other
> direction. Since the unescaping logic dropped the literal backslash
> from the pattern, a text *without* a backslash could wrongly match a
> pattern that requires one:
>
>     SELECT 'backslash' COLLATE ignore_accents LIKE 'back\\slash%';
>     -- unpatched: t (wrong), patched: f (correct)
>
> I think it's worth mentioning this false-positive side of the bug in
> the commit message, since silently-too-permissive LIKE filters are
> arguably the more dangerous symptom for applications.
>

I have updated the commit message. I also added another test for this
scenario in v3.

> 2. A small typo in the new comment in like_match.c:
> "occurences" should be "occurrences".
>

Fixed the typo.

Thanks,
Nitin Motiani
Google

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