Re: Trigger more frequent autovacuums of heavy insert tables

On Wed, Feb 26, 2025 at 12:25 PM Nathan Bossart
<nathandbossart(at)gmail(dot)com> wrote:
>
> On Wed, Feb 26, 2025 at 11:17:06AM -0500, Robert Treat wrote:
> > It strikes me as a bit odd to have this extra wording in the pg_class
> > documentation:
> >
> > + Every all-frozen page must also be marked
> > + all-visible in the visibility map, so
> > + <structfield>relallfrozen</structfield> should be less than or equal to
> > + <structfield>relallvisible</structfield>. However, if either field is
> > + updated manually or if the visibility map is corrupted, it is possible
> > + for <structfield>relallfrozen</structfield> to exceed
> > + <structfield>relallvisible</structfield>.
> >
> > For example, we don't document that rellallvisible should never exceed
> > relpages, and we aren't normally in the habit of documenting weird
> > behavior that might happen if people go updating the system catalogs.
> > Maybe it's just me, but when I read this earlier, I thought there
> > might be some intended use case for updating the catalog manually that
> > you had in mind and so the comments were warranted (and indeed, it's
> > part of why I thought the warning would be useful for users). But upon
> > reading the thread more and another pass through your updated patches,
> > this doesn't seem to be the case, and I wonder if this language might
> > be more encouraging of people updating catalogs than we would
> > typically be.
>
> +1. If we did want to add more information about the ordinary expectations
> of relallfrozen and friends here, I'd suggest doing so in a separate patch.
> IMHO the usual "This is only an estimate..." wording is sufficient for the
> introduction of relallfrozen.

Makes sense. Thanks Robert and Nathan. Attached v11 changes the docs
wording and is rebased.

- Melanie