On Sat, Feb 25, 2006 at 08:15:15AM +0000, Robin Iddon wrote: > From README.pg_autovacuum (and I think 22.1.4 of the 8.1.x document > says the same thing): > > - If the number of (deletes + updates) > VacuumThreshold, then a > vacuum analyze is performed. > > VacuumThreshold is equal to: > vacuum_base_value + (vacuum_scaling_factor * "number of tuples in > the table") By "number of tuples in the table", I'm pretty sure they mean visible tuples; ie: the row count. In any case, I've seen pg_autovacuum work with my own eyes, so as long as it stays running long enough there's no reason it shouldn't end up vacuuming pg_statistics. > In general deletes is 0 for the pg_statistic table so for the default > values we're looking at > > n_tup_upd >= 1000 + (2.0 * reltuples) > > to trigger a vacuum. > > We know for each increment of n_tup_upd, reltuples will receive the same > increment. Thus if the above expression isn't true for any non-zero > starting values of n_tup_upd and reltuples, it won't ever be true: > > If: > n_tup_upd < 1000 + (2.0 * reltuples) > Then: > n_tup_upd+X < 1000 + (2.0 * (reltuples+X)) > > I see that in 8.1.x this has been resolved by defaulting the scale to > 0.4. Rightly or wrongly I have set my scale to 0.3. You should probably drop the threshold to something closer to 200, too. -- Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
