Re: Why clearing the VM doesn't require registering vm buffer in wal record

From: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
To: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Cc: Andres Freund <andres(at)anarazel(dot)de>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Subject: Re: Why clearing the VM doesn't require registering vm buffer in wal record
Date: 2026-09-17 09:24:54
Message-ID: 2CE5B183-BF00-4958-9A93-9B980A554491@yandex-team.ru
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On 16 Sep 2026, Melanie Plageman wrote:
> Vacuum works very hard to never end up with
> PD_ALL_VISIBLE cleared and the VM set. Perhaps we should do everything
> we can to avoid this happening with page modifications as well.

Would it be practical to assert that the VM all-visible bit is clear
whenever we clear PD_ALL_VISIBLE? There may be reasons we don't already
do this that I'm missing, especially during recovery when pages can be
ahead of the record being replayed. It seems like a useful check if we
can find the right conditions for it.

Thank you!

Best regards, Andrey Borodin.

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