Re: Decoupling antiwraparound autovacuum from special rules around auto cancellation

On Fri, Nov 25, 2022 at 2:47 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> Attached WIP patch invents the idea of a regular autovacuum that is
> tasked with advancing relfrozenxid -- which is really just another
> trigger criteria, reported on in the server log in its autovacuum
> reports.

Attached is v2, which is just to fix bitrot. Well, mostly. I did make
one functional change in v2: the autovacuum server log reports now
separately report on table XID age and table MultiXactId age, each as
its own distinct triggering condition.

I've heard informal reports that the difference between antiwraparound
autovacuums triggered by table XID age versus table MXID age can
matter a great deal. It isn't difficult to break out that detail
anyway, so even if the distinction isn't interesting all that often we
might as well surface it to users.

I still haven't made a start on the docs for this. I'm still not sure
how much work I should do on the docs in the scope of this project
versus my project that deals with related issues in VACUUM itself. The
existing material from the "Routine Vacuuming" docs has lots of
problems, and figuring out how to approach fixing those problems seems
kind of daunting right now.

--
Peter Geoghegan