Re: Non-replayable WAL records through overflows and >MaxAllocSize lengths

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Cc: Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Non-replayable WAL records through overflows and >MaxAllocSize lengths
Date: 2022-03-11 21:12:30
Message-ID: CA+TgmoYNbn6TQLY6r5JQup_ok1vpymZFgTVfEycmi7P3ccWJoQ@mail.gmail.com
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On Fri, Mar 11, 2022 at 3:42 PM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> Have you been able to create a test case for that? The largest record I
> can think of is a commit record with a huge number of subtransactions,
> dropped relations, and shared inval messages. I'm not sure if you can
> overflow a uint32 with that, but exceeding MaxAllocSize seems possible.

I believe that wal_level=logical can generate very large update and
delete records, especially with REPLICA IDENTITY FULL.

--
Robert Haas
EDB: http://www.enterprisedb.com

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