On Nov 21, 2010, at 12:16 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > t...@fuzzy.cz writes: >>> Second, I modified the work_mem setting to 2GB (reloaded config) and I see >>> a response time of 38 seconds. Results below from EXPLAIN ANALYZE: > >> How did you reload the config? Using 'kill -HUP pid'? That should work >> fine. Have you cheched 'work_mem' after the reload? > >> Because the explain plans are exactly the same (structure, estimated >> costs). The really interesting bit is this and it did not change at all > >> Buckets: 1024 Batches: 64 Memory Usage: 650kB > > If that didn't change, I'm prepared to bet that the OP didn't actually > manage to change the active value of work_mem.
Yep. All this speculation about slow disks and/or COALESCE strikes me as likely totally off-base. I think the original poster needs to run "show work_mem" right before the EXPLAIN ANALYZE to make sure the new value they set actually stuck. There's no reason for the planner to have used only 650kB if work_mem is set to anything >=2MB. ...Robert -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
