Re: allow changing autovacuum_max_workers without restarting

On Mon, Jan 06, 2025 at 05:36:17PM -0500, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
>> How about trying the higher setting first in initdb? On any sane system
>> that won't cost anything because it'll succeed with the higher value.
>
> That might be a good compromise.

+1, I like the idea.

> You'd have to think about how
> it should interact with initdb's probes for workable values of
> max_connections. My first thought about that is to have initdb
> set autovacuum_worker_slots to max_connections / 8 or thereabouts
> as it works down the list of max_connections values to try. Or
> you could do something more complicated, but I don't see a reason
> to make it too complex.

My first instinct was just to set it to the lowest default we'd consider
during the max_connections tests (which I'm assuming is 3 due to the
current default for autovacuum_max_workers). That way, the max_connections
default won't change from version to version on affected systems, but you
might get some extra autovacuum slots.

--
nathan