Re: XID wraparound in 8.4

Rob Newton escribió:
> Alvaro Herrera wrote:
> >Devrim GÜNDÜZ escribió:
> >
> >>FWIW, PostgreSQL 8.3+ will start autovacuum (even if it is turned off)
> >>if a database is approaching XID wraparound, and get rid of the
> >>problem-- so you don't actually need to check it.
> >
> >8.1 does it too. The main difference is that 8.1 will run a
> >database-wide vacuum, whereas in 8.2 and up it only vacuum tables that
> >have not been vacuumed recently.
>
> Alvaro, we had an 8.1 server that did not start autovacuum when XID
> wraparound was approaching. Rather, it just stopped performing
> transactions, and returned the usual XID wraparound warning.

My guess is that it did start but it failed to do useful work because of
some bug that caused it to die prematurely. There were bugs in early
8.1 that precluded autovacuum from working, so this is not an idle
hypothesis. (The worst part of this story is that the bug would be fire
at some point but the effect could go unseen for months, even after you
installed the patched version.)

If those autovacuum failures go ignored long enough, you get into the
I-don't-want-to-do-anything-until-you-caress-me mode.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.