On 8/11/09 2:14 PM, Josh Berkus wrote: > All, > > I've just been tweaking some autovac settings for a large database, and > came to wonder: why does vacuum_max_freeze_age default to such a high > number? What's the logic behind that? > > AFAIK, you want max_freeze_age to be the largest possible interval of > XIDs where an existing transaction might still be in scope, but no > larger. Yes? > > If that's the case, I'd assert that users who do actually go through > 100M XIDs within a transaction window are probably doing some > hand-tuning. And we could lower the default for most users > considerably, such as to 1 million. (replying to myself) actually, we don't want to set FrozenXID until the row is not likely to be modified again. However, for most small-scale installations (ones where the user has not done any tuning) that's still likely to be less than 100m transactions. -- Josh Berkus PostgreSQL Experts Inc. www.pgexperts.com -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
