Re: allow changing autovacuum_max_workers without restarting

On Tue, Apr 29, 2025 at 01:31:55PM -0400, Tom Lane wrote:
> I wrote:
>> Andres seemed lukewarm about reverting 38da05346 or 6d0154196, so
>> I left it be for the moment. But I still feel the argument is good
>> that "these will do little except confuse future hackers". Barring
>> objection, I'll go revert them.
>
> Actually ... on looking again at 6d0154196 ("Lower default value of
> autovacuum_worker_slots in initdb as needed"), it doesn't look that
> silly. If we're unable to allocate max_connections = 100, turning
> it down while still insisting on 16 AV worker slots doesn't seem
> terribly sane. Maybe we'd choose a formula other than
> "(max_connections / 6)" if we were doing it afresh, but not scaling
> autovacuum_worker_slots at all doesn't seem like the best answer.

Fair point.

> So now I'm inclined to leave that one alone. I'd still revert
> 38da05346, which means the comment added by 6d0154196 needs some minor
> adjustments. But I think we can stick with the "(max_connections /
> 6)" formula --- it will produce 3 with trial_conns = 20, but that's
> enough.

Yup, as long as the lowest possible default is >= the default for
autovacuum_max_workers (3), we're good.

--
nathan