Karl Denninger <karl@xxxxxxxxxxxxx> wrote: Kevin Grittner wrote: >> I suspect that the above might do pretty well in 8.4. > "Exists" can be quite slow. So can "not exists" > > See if you can re-write it using a sub-select - just replace the > "exists ...." with "(select ...) is not null" > > Surprisingly this often results in a MUCH better query plan under > Postgresql. Why the planner evaluates it "better" eludes me (it > shouldn't) but the differences are often STRIKING - I've seen > factor-of-10 differences in execution performance. Have you seen such a difference under 8.4? Can you provide a self-contained example? -Kevin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
