On Mon, 2021-09-06 at 11:59 -0400, Tom Lane wrote: > Laurenz Albe <laurenz.albe@xxxxxxxxxxx> 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. #define BYPASS_THRESHOLD_PAGES 0.02 /* i.e. 2% of rel_pages */ So up to an additional 2% of all pages can have the all-visible bit unset with "index_cleanup = auto". That is probably not worth worrying, right? Yours, Laurenz Albe
