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From: Shinya Kato <shinya11.kato@gmail.com>
Date: Sun, 31 May 2026 22:06:36 +0900
Message-ID: 
 <CAOzEurTC+5xuH_X2EBWjW0Fs9iuTq3OMA=1FfT4xx1wYbCAR6g@mail.gmail.com>
Subject: Re: Report oldest xmin source when autovacuum cannot remove tuples
To: scott@scottray.io
Cc: Laurenz Albe <laurenz.albe@cybertec.at>, Japin Li <japinli@hotmail.com>,
	wenhui qiu <qiuwenhuifx@gmail.com>, Sami Imseih <samimseih@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Sat, May 30, 2026 at 11:31=E2=80=AFAM Scott Ray <scott@scottray.io> wrot=
e:
>
> > I guess the overhead of one more scan of the process array for every au=
tovacuum
> > run if "log_autovacuum_min_duration" is non-zero (which is the default)
> > is acceptable.
>
>
> Could vacuum compute the blocker during ComputeXidHorizons and consume it=
 at log time?
> Avoids the extra scan, and binds the blocker to the horizon vacuum used f=
or pruning.

As Sami suggested in [0], I think this design is a cleaner approach
because it separates the responsibilities of ComputeXidHorizons and
the calculation of vacuum blockers.

[0] https://www.postgresql.org/message-id/CAA5RZ0s%2BUUXekbeGcC-H71kW%3DMfe=
aUCOV%3DyEWX94NXViO2-%3DpA%40mail.gmail.com


--=20
Best regards,
Shinya Kato
NTT OSS Center