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From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Tue, 31 Mar 2026 09:45:08 -0700
Message-ID: 
 <CALj2ACVD0_DhCQ_QOAa7F=nFv8+ZGsHR8SbOc-FmuV8ZrV92HQ@mail.gmail.com>
Subject: Re: Introduce XID age based replication slot invalidation
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
 Masahiko Sawada <sawada.mshk@gmail.com>,
	SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>,
 John H <johnhyvr@gmail.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
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 <https://www.postgresql.org/message-id/CALj2ACVD0_DhCQ_QOAa7F%3DnFv8%2BZGsHR8SbOc-FmuV8ZrV92HQ%40mail.gmail.com>
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Hi,

On Tue, Mar 31, 2026 at 12:25=E2=80=AFAM Hayato Kuroda (Fujitsu)
<kuroda.hayato@fujitsu.com> wrote:
>
> Dear Bharath,
>
> Thanks for re-working the project.

Thank you for looking into this.

> While seeing the old discussion, I found that Robert Haas was agaist the =
XID-based
> invalidation, because it's difficult to determine the cutoff age [1].
> Can you clarify your thought against the point? Are you focusing on solvi=
ng the
> wraparound issues, not for bloated instance issue?
> The code may not be accepted unless we got his agreement.
>
> [1]: https://www.postgresql.org/message-id/CA+TgmoZTbaaEjSZUG1FL0mzxAdN3q=
mXksO3O9_PZhEuXTkVnRQ@mail.gmail.com

I summarized what others (Nathan, Robert, Amit, Alvaro, Bertrand) said
about it here with my responses:
https://www.postgresql.org/message-id/CALj2ACVY%2BFd5vC0VjW%3D5VDK9mmt-Y%2B=
PDZxnBp8ngGAZc24Vv9g%40mail.gmail.com.

Please have a look.

A good setting for this in production scenarios is to set
max_slot_xid_age to vacuum_failsafe_age (1.6B) or little less, so that
autovacuum invalidates the slot before entering failsafe mode,
unblocking datfrozenxid advancement and avoiding XID wraparound
without manual VACUUM or downtime. I added a test for this in the 0002
patch. Please have a look.

--
Bharath Rupireddy
Amazon Web Services: https://aws.amazon.com