Robert Haas <robertmh...@gmail.com> wrote: > Right now, whether or not to autovacuum is the rest of a two-pronged
> test. The first prong is based on number of updates and deletes > relative to table size; that triggers a regular autovacuum. The > second prong is based on age(relfrozenxid) and triggers a > non-page-skipping vacuum (colloquially, an anti-wraparound vacuum). > > The typical case in which this doesn't work out well is when the table > has a lot of inserts but few or no updates and deletes. So I propose > that we change the first prong to count inserts as well as updates and > deletes when deciding whether it needs to vacuum the table. We > already use that calculation to decide whether to auto-analyze, so it > wouldn't be very novel. We know that the work of marking pages > all-visible will need to be done at some point, and doing it sooner > will result in doing it in smaller batches, which seems generally > good. > > However, I do have one concern: it might lead to excessive > index-vacuuming. Right now, we skip the index vac step only if there > ZERO dead tuples are found during the heap scan. Even one dead tuple > (or line pointer) will cause an index vac cycle, which may easily be > excessive. So I further propose that we introduce a threshold for > index-vac; so that we only do index vac cycle if the number of dead > tuples exceeds, say 0.1% of the table size. +1 I've been thinking of suggesting something along the same lines, for the same reasons. -- Kevin Grittner EDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
