On 2013-11-27 14:53:27 -0500, Noah Misch wrote:
> How would you characterize the chances of this happening with default
> *vacuum_freeze_*_age settings? Offhand, it seems you would need to encounter
> this bug during each of ~10 generations of autovacuum_freeze_max_age before
> the old rows actually become invisible.
On second thought, it's quite possible to see problems before that
leading to more problems. A single occurance of such a illegitimate
increase in relfrozenxid can be enough to cause problems of a slightly
different nature.
As relfrozenxid has been updated we might now, or after vacuuming some
other tables, become elegible to truncate the clog. In that case we'll
get ERRORs about "could not access status of transaction" if the tuple
hasn't been fully hinted when scanning it later.
Greetings,
Andres Freund
-- Andres Freund http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services