I was looking at the autovacuum documentation: http://www.postgresql.org/docs/9.0/interactive/routine-vacuuming.html#AUTOVACUUM For analyze, a similar condition is used: the threshold, defined as: analyze threshold = analyze base threshold + analyze scale factor * number of tuples is compared to the total number of tuples inserted or updated since the last ANALYZE. I guess that should be updated to read "insert, updated or deleted". On Mon, Sep 20, 2010 at 10:12 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Joe Miller <joe.d.miller@xxxxxxxxx> writes: >> The autovacuum daemon currently uses the number of inserted and >> updated tuples to determine if it should run VACUUM ANALYZE on a >> table. Why doesn’t it consider deleted tuples as well? > > I think you misread the code. > > Now there *is* a problem, pre-9.0, if your update pattern is such that > most or all updates are HOT updates. To quote from the 9.0 alpha > release notes: > > Revise pgstat's tracking of tuple changes to > improve the reliability of decisions about when to > auto-analyze. The previous code depended on n_live_tuples + > n_dead_tuples - last_anl_tuples, where all three of these > numbers could be bad estimates from ANALYZE itself. Even > worse, in the presence of a steady flow of HOT updates and > matching HOT-tuple reclamations, auto-analyze might never > trigger at all, even if all three numbers are exactly right, > because n_dead_tuples could hold steady. > > It's not clear to me if that matches your problem, though. > > regards, tom lane > -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
