Re: Decoupling antiwraparound autovacuum from special rules around auto cancellation

On Thu, Jan 19, 2023 at 12:58 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> There's absolutely no guarantee that autoanalyze is triggered
> there. Particularly with repeated vacuums triggered due to an relfrozenxid age
> that can't be advanced that very well might not happen within days on a large
> relation.

Arguments like that work far better as arguments in favor of the
vac_estimate_reltuples heuristics.

That doesn't mean that the heuristics are good in any absolute sense,
of course. They were just a band aid intended to ameliorate some of
the negative impact that came from treating scanned_pages as a random
sample. I think that we both agree that the real problem is that
scanned_pages just isn't a random sample, at least not as far as
reltuples/live tuples is concerned (for dead tuples it kinda isn't a
sample, but is rather something close to an exact count).

I now understand that you're in favor of addressing the root problem
directly. I am also in favor of that approach. I'd be more than happy
to get rid of the band aid as part of that whole effort.

--
Peter Geoghegan