On Wed, Apr 8, 2020 at 9:43 AM Tomas Vondra <tomas.von...@2ndquadrant.com> wrote: > > On Wed, Apr 08, 2020 at 12:51:05PM +0200, Tomas Vondra wrote: > >On Tue, Apr 07, 2020 at 11:54:23PM -0400, Tom Lane wrote: > >>hyrax is not too happy with this test: > >> > >>https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=hyrax&dt=2020-04-07%2004%3A55%3A15 > >> > >>It's not too clear to me why CLOBBER_CACHE_ALWAYS would be breaking > >>EXPLAIN output, but it evidently is. > >> > > > >Thanks, I'll investigate. It's not clear to me either what might be > >causing this, but I guess something must have gone wrong in > >estimation/planning. > > > > OK, I know what's going on - it's a rather embarassing issue in the > regression test. There's no analyze on the test tables, so it uses > default estimates for number of groups etc. But with clobber cache the > test runs long enough for autoanalyze to kick in and collect stats, so > we generate better estimates which changes the plan. > > I'll get this fixed - explicit analyze and tweaking the data a bit > should do the trick.
Looking at the tests that failed, I think we should consider just adding: set enable_sort = off; because several of those tests have very specific amounts of data to ensure we test the transition points around the different modes in the incremental sort node. James
