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: 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: 2026-08-14 04:40:56
Message-ID: an6cWBJAc7QN1F2A@bdtpg
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Hi,

On Wed, Aug 12, 2026 at 05:00:00PM -0700, Bharath Rupireddy wrote:
> I believe this can happen in practice (as explained above). IMHO, XID
> age based slot invalidation must invalidate the synced slot on the
> standby

Yeah, I agree. Keeping the exemption for idle_replication_slot_timeout but
removing it from CanInvalidateXidAgedSlot() makes sense to me.

One nuance about 3/ though: the synced slot is current in that case and the
stale catalog_xmin is stored on the primary's physical slot. Therefore, the check
for aged synced slots would not address this case: the synced slot is not aged,
so it would not be invalidated.

Worth adding a test with an actual synced slot, including checking that its
invalidation releases the feedback horizon on the primary?

Regards,

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

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