Re: Apparent Wraparound?

Gunther Mayer wrote:
> Hi there,
>
> I just found the following message in my logs:
>
> Jun 8 10:38:38 caligula postgres[56868]: [1-1] : LOG: could not
> truncate directory "pg_subtrans": apparent wraparound
>
> Should I be worried or can I just ignore this one? My database is still
> small (a pg_dumpall bzippe'd is still around 500KB) so I doubt that I'm
> affected by any transaction id wraparound problems. I also vacuum
> analyze once a day and have pg_autovacuum turned on.

What version are you running? This seems to match the description of a
bug fixed for 8.2 and 8.1.5:

revision 1.20
date: 2006-07-19 20:46:42 -0400; author: tgl; state: Exp; lines: +8 -3;
Don't try to truncate multixact SLRU files in checkpoints done during xlog
recovery. In the first place, it doesn't work because slru's
latest_page_number isn't set up yet (this is why we've been hearing reports
of strange "apparent wraparound" log messages during crash recovery, but
only from people who'd managed to advance their next-mxact counters some
considerable distance from 0). In the second place, it seems a bit unwise
to be throwing away data during crash recovery anwyway. This latter
consideration convinces me to just disable truncation during recovery,
rather than computing latest_page_number and pushing ahead.

--
Alvaro Herrera http://www.amazon.com/gp/registry/CTMLCN8V17R4
"La verdad no siempre es bonita, pero el hambre de ella sí"