From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix text substring search for non-deterministic collations.
Date: Sat, 06 Dec 2025 01:10:44 +0000
Message-ID: <E1vRgot-0031SX-38@gemulon.postgresql.org> (raw)
Fix text substring search for non-deterministic collations.
Due to an off-by-one error, the code failed to find matches at the
end of the haystack. Fix by rewriting the loop.
While at it, fix a comment that claimed that the function could find
a zero-length match. Such a match could send a caller into an endless
loop. However, zero-length matches only make sense with an empty
search string, and that case is explicitly excluded by all callers.
To make sure it stays that way, add an Assert and a comment.
Bug: #19341
Reported-by: Adam Warland <adam.warland@infor.com>
Author: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/19341-1d9a22915edfec58@postgresql.org
Backpatch-through: 18
Branch
------
REL_18_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/18b349315ae7e00261732f514d6c91d713bb77d0
Modified Files
--------------
src/backend/utils/adt/varlena.c | 25 ++++++++++++++++++-------
src/test/regress/expected/collate.icu.utf8.out | 7 +++++++
src/test/regress/sql/collate.icu.utf8.sql | 3 +++
3 files changed, 28 insertions(+), 7 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: tgl@sss.pgh.pa.us, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix text substring search for non-deterministic collations.
In-Reply-To: <E1vRgot-0031SX-38@gemulon.postgresql.org>
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