Re: Trigger more frequent autovacuums of heavy insert tables

On Wed, Feb 19, 2025 at 4:59 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> On Wed, Feb 19, 2025 at 04:36:05PM -0500, Melanie Plageman wrote:
> > This makes me think I should also not cap relallfrozen when using it
> > in relation_needs_vacanalyze(). There I cap it to relallvisible and
> > relallvisible is capped to relpages. One of the ideas behind letting
> > people modify these stats in pg_class is that they can change a single
> > field to see what the effect on their system is, right?
>
> Right.  Capping these values to reflect reality seems like it could make
> that more difficult.

Attache v7 doesn't cap the result for manual stats updating done with
relation_statistics_update(). I did, however, keep the cap for the
places where vacuum/analyze/create index update the stats. There the
number for relallfrozen is coming directly from visibilitymap_count(),
so it should be correct. I could perhaps add an assert instead, but I
didn't think that really made sense. An assert is meant to help the
developer and what could the developer do about the visibility map
being corrupted.

> >> Should we allow manipulating relallfrozen like we do relallvisible?  My
> >> assumption is that would even be required for the ongoing statistics
> >> import/export work.
> >
> > Why would it be required for the statistics import/export work?
>
> It's probably not strictly required, but my naive expectation would be that
> we'd handle relallfrozen just like relallvisible, which appears to be
> dumped in the latest stats import/export patch.  Is there any reason we
> shouldn't do the same for relallfrozen?

Nope I don't think so, but I also don't know about how people are
envisioning using a manually updated relallvisible.

- Melanie