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From: Shinya Kato <shinya11.kato@gmail.com>
Date: Tue, 4 Nov 2025 10:29:26 +0900
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Subject: Re: Report oldest xmin source when autovacuum cannot remove tuples
To: wenhui qiu <qiuwenhuifx@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Fri, Oct 31, 2025 at 5:01=E2=80=AFPM wenhui qiu <qiuwenhuifx@gmail.com> =
wrote:
>
> HI
>   Thank you for your path ,This path is extremely helpful.

Thank you!

> > +/*
> > + * Identifies what determined a relation's OldestXmin horizon.
> > + * Used by autovacuum to report why dead tuples were not removable.
> > + */
> > +typedef enum OldestXminSource
> > +{
> > + OLDESTXMIN_SOURCE_ACTIVE_TRANSACTION,
> > + OLDESTXMIN_SOURCE_HOT_STANDBY_FEEDBACK,
> > + OLDESTXMIN_SOURCE_PREPARED_TRANSACTION,
> > + OLDESTXMIN_SOURCE_REPLICATION_SLOT,
> > + OLDESTXMIN_SOURCE_OTHER
> > +} OldestXminSource;
> > +
> > +typedef struct OldestXminInfo
> > +{
> > + OldestXminSource source;
> > + int backend_pid;
> > +} OldestXminInfo;
> I have a question for like this
> one session
> begin;
> select * from table_a
> not commit or not closed session
> It is in OLDESTXMIN_SOURCE_ACTIVE_TRANSACTION type ?

Exactly. Looking at 010_autovacuum_oldest_xmin_reason.pl should make
it clear which logs are output in which cases. (I just noticed there
seems to be a case where the test fails. I need to fix that.)

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