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From: Kirill Reshke <reshkekirill@gmail.com>
Date: Fri, 30 Jan 2026 14:25:17 +0500
Message-ID: <CALdSSPhFrQ4=N6yJ0N4pQ=RKjeSfU7N3wz7xpLTwsUjLc-6Tdg@mail.gmail.com>
Subject: Re: eliminate xl_heap_visible to reduce WAL (and eventually set VM on-access)
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Alexander Lakhin <exclusion@gmail.com>, Andres Freund <andres@anarazel.de>, 
	Andrey Borodin <x4mmm@yandex-team.ru>, Chao Li <li.evan.chao@gmail.com>, 
	Xuneng Zhou <xunengzhou@gmail.com>, Robert Haas <robertmhaas@gmail.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>
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On Thu, 29 Jan 2026 at 20:16, Melanie Plageman
<melanieplageman@gmail.com> wrote:
>
> On Thu, Jan 29, 2026 at 8:39=E2=80=AFAM Kirill Reshke <reshkekirill@gmail=
.com> wrote:
> >
> > Thanks Alexander!
> > This is a good and detailed report, I was able to reproduce this.
>
> Thanks to both of you for looking into it!
>
> > I have added some logs to my copy of postgres with your patch and I
> > think problem causing this test to fail is this sequence:
> >
> > 1) Autovacuum starts, does its deeds, and acquiring xid =3D 118518
>
> So, in this scenario, is the issue that autovacuum runs before vacuum
> freeze? If so, we can change the table DDL to:
>
> create table test_vac_unmodified_heap(a int) with (autovacuum_enabled =3D=
 false);
>
> which would prevent the autovacuum from running.
>
> Unless there is some other way for one of the other tests to hold
> OldestXmin back to before the xid of the insert. But I don't see how.
>
> > 2) insert into test_vac_unmodified_heap values (1); executes and
> > commits with xid =3D 118519 (from my log)
> > 3) vacuum freeze starts and computes cutoff xid =3D 118518, because
> > oldest xmin is 118518 from (1)
> >
> > *and we cannot freeze tuple*
>
> - Melanie


Sorry, I messed up my previous email.

> create table test_vac_unmodified_heap(a int) with (autovacuum_enabled =3D=
 false);

Yes I did try this, but it does not help, because autovacuum runs on
catalog relations, still causing fail.

We cannot disable autovac globally in regression suite, so I propose
to changes this to TAp test


--=20
Best regards,
Kirill Reshke