Re: allow changing autovacuum_max_workers without restarting

On Thu, Apr 18, 2024 at 05:05:03AM +0000, Imseih (AWS), Sami wrote:
> I looked at the patch set. With the help of DEBUG2 output, I tested to ensure
> that the the autovacuum_cost_limit balance adjusts correctly when the
> autovacuum_max_workers value increases/decreases. I did not think the
> patch will break this behavior, but it's important to verify this.

Great.

> 1. A nit. There should be a tab here.
>
> - dlist_head av_freeWorkers;
> + dclist_head av_freeWorkers;

I dare not argue with pgindent.

> 2. autovacuum_max_worker_slots documentation:
>
> + <para>
> + Note that the value of <xref linkend="guc-autovacuum-max-workers"/> is
> + silently capped to this value.
> + </para>
>
> This comment looks redundant in the docs, since the entry
> for autovacuum_max_workers that follows mentions the
> same.

Removed in v2. I also noticed that I forgot to update the part about when
autovacuum_max_workers can be changed. *facepalm*

> 3. The docs for autovacuum_max_workers should mention that when
> the value changes, consider adjusting the autovacuum_cost_limit/cost_delay.
>
> This is not something new. Even in the current state, users should think about
> these settings. However, it seems even important if this value is to be
> dynamically adjusted.

I don't necessarily disagree that it might be worth mentioning these
parameters, but I would argue that this should be proposed in a separate
thread.

--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com