OK, thanks to RhodiumToad on IRC, I was able to determine the cause of the two reported pg_upgrade problems he saw via IRC. It seems toast tables have xids and pg_dump is not preserving the toast relfrozenxids as it should. Heap tables have preserved relfrozenxids, but if you update a heap row but don't change the toast value, and the old heap row is later removed, the toast table can have an older relfrozenxids than the heap table.
The fix for this is to have pg_dump preserve toast relfrozenxids, which can be easily added and backpatched. We might want to push a 9.0.4 for this. Second, we need to find a way for people to detect and fix existing systems that have this problem, perhaps looming when the pg_class relfrozenxid passes the toast relfrozenxid, and thirdly, we need to figure out how to get this information to users. Perhaps the communication comes through the 9.0.4 release announcement. Yes, this is not good! :-( I will still add a special flag to postgres to turn off autovacuum, but as we suspected, this is only a marginal improvement and not the cause of the 9.0.X failures. The good news is that only two people have seen this problem and it only happens when the hint bits have not been set on the toast rows and the oldest heap rows have been updated. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
