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From: Dominique Devienne <ddevienne@gmail.com>
Date: Thu, 8 Jan 2026 13:48:58 +0100
Message-ID: <CAFCRh--H4a9kV4R=22DB6cL+KxcJ3A6-3tg_Y77KgTdDJECBwA@mail.gmail.com>
Subject: Re: Collation again here
To: Rihad <grihad@gmail.com>
Cc: pgsql-general General <pgsql-general@postgresql.org>
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On Thu, Jan 8, 2026 at 1:39=E2=80=AFPM Rihad <grihad@gmail.com> wrote:
> Hi, guys. Just pg_upgraded our PG from 13.x to 18.1, rebuilt all indexes =
concurrently and issued  ALTER DATABASE foo REFRESH COLLATION VERSION
> Everything's fine on the master server, no warnings etc. Then I set up a =
replica using pg_basebackup, and there when trying to access the DB using p=
sql I get:
>
> WARNING:  database "foo" has a collation version mismatch
> DETAIL:  The database was created using collation version 43.0, but the o=
perating system provides version 34.0.
> HINT:  Rebuild all objects in this database that use the default collatio=
n and run ALTER DATABASE foo REFRESH COLLATION VERSION, or build PostgreSQL=
 with the right library version.
> The OS are both FreeBSD, but the master runs 14.3, the replica runs 13.5.=
 PostgreSQL packages are built with ICU support by default, the versions us=
ed are identical:  icu-76.1
> Could it be that the OS (libc) needs to be the same version? I hoped it w=
ould be enough to use the same ICU.

Depends what Provider you used in those DBs:
https://www.postgresql.org/docs/current/locale.html#LOCALE-PROVIDERS
Having the same ICU is good, but do your DBs use that provider? If
not, and you're using the libc one, then yes, the libc version
matters.
Myself I use the new builtin provider to avoid OS portability issues. --DD