On Fri, Feb 22, 2013 at 5:57 AM, Stefan Andreatta <s.andrea...@synedra.com>wrote:
> Hi, > > If I understand http://www.postgresql.org/**docs/9.1/static/routine-** > vacuuming.html<http://www.postgresql.org/docs/9.1/static/routine-vacuuming.html>correctly, > the autovacuum threshold in could be estimated like this in > PostgreSQL 9.1: > > SELECT pg_stat_user_tables.relname, > pg_stat_user_tables.n_dead_**tup, > CAST(current_setting('**autovacuum_vacuum_threshold') AS bigint) > + (CAST(current_setting('**autovacuum_vacuum_scale_**factor') AS > numeric) > * pg_class.reltuples) AS av_threshold > FROM pg_stat_user_tables > JOIN pg_class on pg_stat_user_tables.relid = pg_class.oid > ORDER BY 1; > > If pg_stat_user_tables.n_dead_tup exceeds av_threshold autovacuum should > kick in. Obviously, that does rely on up-to-date statistics. Is that how it > is actually done? > Pretty much, yes. With the caveat that table storage settings can override the global settings. > > 2nd question: because pg_stat_user_tables.n_dead_tup is itself estimated > by ANALYZE it cannot be used as a criterion for the next autoanalyze run, I > think. n_dead_tup is updated by the stats collector, not by ANALYZE. Cheers, Jeff
