Re: Introduce XID age based replication slot invalidation

From: Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>
To: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Cc: Nisha Moond <nisha(dot)moond412(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Srinath Reddy Sadipiralla <srinath2133(at)gmail(dot)com>, SATYANARAYANA NARLAPURAM <satyanarlapuram(at)gmail(dot)com>, "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, John H <johnhyvr(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Introduce XID age based replication slot invalidation
Date: 2026-09-22 09:19:35
Message-ID: arJIJ3MbrWD6uKXG@bdtpg
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Hi,

On Fri, Sep 18, 2026 at 10:40:00AM -0700, Bharath Rupireddy wrote:
>
> One approach is to never invalidate the slot, and to honour
> max_slot_xid_age by stopping conflict info retention for whoever is
> holding the slot's xmin back. On the worker side, the existing
> should_stop_conflict_info_retention() stops retention when the
> worker's oldest xid has aged past the age limit, whether or not a
> retention duration is set. On the launcher side, once per cycle, right
> after it tries to advance the xmin as usual, if the xmin has aged past
> the age limit it stops retention by setting subretentionactive to
> false in pg_subscription

How do you see the launcher updating pg_subscription here? Are you thinking of a
launcher specific update path?

> I prefer the first approach,

+1 on the first approach. It is what I had in mind when suggesting combining the
worker and launcher checks.

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

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