Re: Behavior change in PostgreSQL 14Beta3 or bug?

Laurenz Albe <laurenz.albe@cybertec.at> writes:
> It is not an incompatibility that warrants a mention in the release notes,
> but perhaps somthing in
> https://www.postgresql.org/docs/14/indexes-index-only-scans.html
> and/or
> https://www.postgresql.org/docs/14/routine-vacuuming.html#VACUUM-FOR-VISIBILITY-MAP
> could be added that recommends that people should consider frequent
> VACUUM with "index_cleanup = on" for best performance with index-only scans.

If enough pages would change their all-visible state to make a significant
difference in index-only scan performance, VACUUM should not be skipping
the cleanup.  If it is, the threshold for that is too aggressive.

Assuming that that choice was made appropriately, I think the advice you
propose here will just cause people to waste lots of cycles on VACUUM
runs that have only marginal effects.

            regards, tom lane