Message-ID: <60b467ac47d5c6bbb9c21c3bdfecce8e5de60cda.camel@cybertec.at>
Subject: Re: BUG #19341: REPLACE() fails to match final character when using
 nondeterministic ICU collation
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: adam.warland@infor.com, pgsql-bugs@lists.postgresql.org
Date: Tue, 02 Dec 2025 17:24:54 +0100
In-Reply-To: <19341-1d9a22915edfec58@postgresql.org>
References: <19341-1d9a22915edfec58@postgresql.org>
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On Tue, 2025-12-02 at 10:03 +0000, PG Bug reporting form wrote:
> PostgreSQL version: 18.1
>=20
> When using a nondeterministic ICU collation, the replace() function fails=
 to
> replace a substring when that substring appears at the end of the input
> string.
>=20
> Occurrences of the same substring earlier in the string are replaced
> normally.
>=20
> Specific collation used:
> create collation test_nondeterministic (
>     provider =3D icu,
>     locale =3D 'und-u-ks-level2',
>     deterministic =3D false
> )
>=20
> -- Replace final character under nondeterministic collation
> SELECT replace(
>     'testx' COLLATE "test_nondeterministic",
>     'x'     COLLATE "test_nondeterministic",
>     'y') AS res1;

I can reproduce the problem, and the attached patch fixes it for me.

I am not certain if it is safe to apply pg_mblen() to "haystack_end", thoug=
h.

Yours,
Laurenz Albe