On Thu, Jul 18, 2013 at 9:14 AM, Pavel Stehule <pavel.steh...@gmail.com> wrote: > Hello > > I found a slow query with large external sort. I expect, so external > sort should be penalized. Is it?
It tries to, but it doesn't seem to be much good at it. In particular, I think it does a poor job of estimating the CPU cost of an external sort relative to an in-memory sort of a slightly smaller data set. In my experience adding the single tuple that actually pushes you over the work_mem limit costs about 3x in CPU. It is one of those things I started looking into a few times, but never got anywhere before getting distracted. Cheers, Jeff -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
