Don Seiler wrote: > On Mon, Dec 4, 2017 at 4:02 PM, Alvaro Herrera <alvherre@xxxxxxxxxxxxxx> > wrote: > > The docs are telling half the truth when they say this is a > > not-bug-but-feature, though. It's true that we don't want to overwrite > > some of these counters, such as number of scans, number of tuples > > accessed, etc; but ideally we should keep things such as vacuum/analyze > > counts and last times, and also the counts of dead/live/ > > mod_since_analyze tuples, to keep autovacuum informed without requiring > > an ANALYZE. > > I'm not so worried about the time of last vacuum or analyze but the > statistics for optimizer usage would be necessary. The optimizer stats are not lost on crash or promote actually; these are stored in pg_statistic (not in the stats collector) and *are* part of regular "data". > Otherwise I would think > the time to complete a failover would have to include that "vacuumdb --all > --analyze-only" run as queries run before that could be very out-of-sorts > with no information on the data. Although perhaps I'm misunderstanding > where the optimizer gets its information from and these pg_stat_% tables > are not what I seem to think they are. I think it's pretty common misunderstanding -- it's not easy to see the boundary between pg_statistic and pg_stat_* tables. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
