> So I think we need to sort by age(relfrozenxid) in tables that are over
> the anti-wraparound limit. Given your code that doesn't seem to be that
> hard?
I might also suggest that we think about changing the defaults for
wraparound vacuum behavior. Partcularly, the fact that
vacuum_freeze_min_age is 50% of autovacuum_freeze_max_age by default is
optimal for absolutely nobody, and forces re-wraparound vacuuming of
wraparound tables which were just recently wraparound-vacuumed. We
should lower vacuum_freeze_min_age to something sane, like 1000000.
(background:
http://www.databasesoup.com/2012/10/freezing-your-tuples-off-part-2.html)
Also, while I don't know if Alvaro's optimization is a net gain or not
(It might be), I do agree that backpatching it is not worth considering.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com