On Wed, Aug 18, 2021 at 3:58 PM Peter Geoghegan <p...@bowt.ie> wrote: > On Tue, Aug 17, 2021 at 5:31 PM Peter Geoghegan <p...@bowt.ie> wrote: > > > Now what's the threshold? 20 out of 100? 50? 80? > > > > I'm not going to pretend to know the answer. But I will point out that > > one DB system whose heap fill factor defaults to 90 seems to have a > > symmetric setting for the "open up page again" point -- the default > > for that is 40. Not sure that that really matters to us, but that does > > seem pretty low to me. It's very sticky indeed. > > Correction: it's actually 60, not 40. > > It's true that the actual default is 40, but it works the other way > around relative to Postgres (as does the related fill factor like > setting, which defaults to 90 instead of 100). And so we would think > of this other "open up closed page once again" setting as having a > default of 60. (Or perhaps we'd think of it as having a default that > is 2/3 of the closely related fill factor setting's default.)
I don't know whether 60 is optimal or not, but it doesn't seem crazy. -- Robert Haas EDB: http://www.enterprisedb.com
