Tom Lane wrote: > The argument that autovac workers need fresher stats than anything else > seems pretty dubious to start with. Why shouldn't we simplify that down > to "they use PGSTAT_STAT_INTERVAL like everybody else"?
The point of wanting fresher stats than that, eons ago, was to avoid a worker vacuuming a table that some other worker vacuumed more recently than PGSTAT_STAT_INTERVAL. I realize now that the semantics we really want was something like "stats no older than XYZ" where the given value is the timestamp at which we start checking; if we get anything newer than that it would be okay, but we currently reject it because of lack of a more appropriate API. (If it takes more than PGSTAT_STAT_INTERVAL to get the stats back, a regular backend would ask for fresher stats, but to an autovac worker they would be good enough as long as they are newer than its recheck start time.) Nowadays we can probably disregard the whole issue, since starting a new vacuum just after the prior one finished should not cause much stress to the system thanks to the visibility map. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
