Re: statistics for shared catalogs not updated when autovacuum is off

On 2/1/16 7:20 PM, Peter Eisentraut wrote:
> That's probably right. Even with autovacuum on, the statistics for
> shared catalogs do not appear as updated right away. That is, if you
> run VACUUM and then look at pg_stat_sys_tables right away, you will see
> the stats for shared catalogs to be slightly out of date until the
> minutely autovacuum check causes them to update.
>
> So the problem exists in general, but the autovacuum launcher papers
> over it every minute.

I suspect the issue is in backend_read_statsfile(). Presumably the if
just needs a call to AutoVacuumingActive() added:

> /*
> * Autovacuum launcher wants stats about all databases, but a shallow read
> * is sufficient.
> */
> if (IsAutoVacuumLauncherProcess())
> pgStatDBHash = pgstat_read_statsfiles(InvalidOid, false, false);
> else
> pgStatDBHash = pgstat_read_statsfiles(MyDatabaseId, false, true);

The interesting thing is that we always start the launcher one time, to
protect against wraparound, but apparently that path doesn't call
anything that calls backend_read_statsfile() (which is static).
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com