On Mon, May 20, 2013 at 3:11 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Armand du Plessis <adp@bank.io> writes: > The autovacuum completed (after many hours) however it didn't seem to have > frozen any old pages as it just kicks off again right away with the same > reason (VACUUM ANALYZE public.messages (to prevent wraparound))
I suspect it's unable to move the table's min XID forward at all because there is some old open transaction preventing cleanup of very old dead tuples. Look for old xact_start times in pg_stat_activity. Also look for old entries in pg_prepared_xacts. If you find any, get rid of them.
Thanks Tom, that sounds like it possibly could've caused it. I've since restarted the cluster (kicking myself) so there's no old transactions left in either table. (pg_prepared_xacts is actually empty). Will check there first if this happens again.