Re: Visibility map and freezing

Peter Eisentraut wrote:
> Heikki Linnakangas wrote:
>> I think we need a threshold similar to autovacuum_freeze_max_age for
>> manual vacuums as well: vacuum_freeze_max_age. If you run VACUUM, and
>> relfrozenxid is older than vacuum_freeze_max_age, the visibility map
>> is ignored and all pages are scanned.
>
> Would one parameter to control both suffice? (i.e., rename
> autovacuum_freeze_max_age to vacuum_freeze_max_age)

Imagine that you run a nightly VACUUM from cron, and have autovacuum
disabled. If autovacuum_freeze_max_age is the same as
vacuum_freeze_max_age, as soon as that age is reached, an
anti-wraparound autovacuum launched. What we'd want to happen is for the
next nightly VACUUM to do the work instead. So they need to be separate
settings, with some space between them by default.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com