Date: Tue, 9 Jul 2024 17:01:23 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>,
	Bertrand Drouvot <bertranddrouvot.pg@gmail.com>,
	shveta malik <shveta.malik@gmail.com>,
	Masahiko Sawada <sawada.mshk@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Introduce XID age and inactive timeout based replication slot
 invalidation
Message-ID: <Zo2zMwVuMcB79OH2@nathan>
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On Mon, Jun 24, 2024 at 11:30:00AM +0530, Bharath Rupireddy wrote:
> 6) Vacuum command can't be run on the standby in recovery. So, to help
> invalidate replication slots on the standby, I have for now let the
> checkpointer also do the XID age based invalidation. I know
> invalidating both in checkpointer and vacuum may not be a great idea,
> but I'm open to thoughts.

Hm.  I hadn't considered this angle.

> a) Let the checkpointer do the XID age based invalidation, and call it
> out in the documentation that if the checkpoint doesn't happen, the
> new GUC doesn't help even if the vacuum is run. This has been the
> approach until v40 patch.

My first reaction is that this is probably okay.  I guess you might run
into problems if you set max_slot_xid_age to 2B and checkpoint_timeout to 1
day, but even in that case your transaction ID usage rate would need to be
pretty high for wraparound to occur.

-- 
nathan