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From: Sami Imseih <samimseih@gmail.com>
Date: Thu, 23 Oct 2025 14:32:50 -0500
Message-ID: 
 <CAA5RZ0sfQ-VSCSafsrvyJ7wsW1utLwtPVJ5N6hB0726BGRDrgQ@mail.gmail.com>
Subject: Re: another autovacuum scheduling thread
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Robert Haas <robertmhaas@gmail.com>,
	Jeremy Schneider <schneider@ardentperf.com>, pgsql-hackers@postgresql.org
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> On Thu, Oct 23, 2025 at 01:22:24PM -0500, Sami Imseih wrote:
> > I was looking at v3, and I understand the formula will be updated in th=
e
> > next version. However, do you think we should benchmark the approach
> > of using an intermediary list to store the eligible tables and sorting
> > that list,
> > which may cause larger performance overhead for databases with hundreds
> > of tables that may all be eligible for autovacuum. I do think such case=
s
> > out there are common, particularly in multi-tenant type databases, wher=
e
> > each tenant could be one or more tables.
>
> We already have an intermediary list of table OIDs, so the additional
> overhead is ultimately just the score calculation and the sort operation.
> I'd be quite surprised if that added up to anything remotely worrisome,
> even for thousands of eligible tables.

Yeah, you=E2=80=99re correct, the list already exists; sorry I missed that.=
 My
main concern is
the additional overhead of the sort operation, especially if we have
many eligible
tables and an aggressive autovacuum_naptime. I don=E2=80=99t think we shoul=
d make the
existing performance of many relations any worse with an additional
sort. That said,
in such cases the sort may not even be the main performance
bottleneck, since the
catalog scan itself already doesn=E2=80=99t scale well with many relations.
With our current
approach, we have more options to improve this, but if we add a sort,
we may not be
able to avoid a full scan.

--
Sami