Peter Schuller wrote: > Does anyone have input on why this could be happening? The PostgreSQL > version is 8.2.4[1]. Am I correct in that it *should* not be possible > for this to happen?
No. VACUUM takes an exclusive lock at the end of the operation to truncate empty pages. (If it cannot get the lock then it'll just skip this step.) In 8.2.4 there was a bug that caused it to sleep according to vacuum_delay during the scan to identify possibly empty pages. This was fixed in 8.2.5: revision 1.81.2.1 date: 2007-09-10 13:58:50 -0400; author: alvherre; state: Exp; lines: +6 -2; Remove the vacuum_delay_point call in count_nondeletable_pages, because we hold an exclusive lock on the table at this point, which we want to release as soon as possible. This is called in the phase of lazy vacuum where we truncate the empty pages at the end of the table. An alternative solution would be to lower the vacuum delay settings before starting the truncating phase, but this doesn't work very well in autovacuum due to the autobalancing code (which can cause other processes to change our cost delay settings). This case could be considered in the balancing code, but it is simpler this way. -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance