On Fri, Jul 1, 2016 at 11:45 AM, Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: > Merlin Moncure wrote: > >> It's pretty easy to craft a query where you're on the winning side, >> but what's the worst case of doing two pass...is constant folding a >> non trivial fraction of planning time? > > One thing that has been suggested is to re-examine the plan after > planning is done, and if execution time is estimated to be large (FSVO), > then run a second planning pass with more expensive optimizations > enabled to try and find better plans. The guiding principle would be to > continue to very quickly find good enough plans for > frequent/small/simple queries, but spend more planning effort on more > complex ones where execution is likely to take much longer than planning > time. > > So doing constant-folding twice would be enabled for the second planning > pass.
I like this idea. Maybe a GUC controlling the cost based cutoff (with 0 meaning, "assume the worst and plan the hard way first"). merlin -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers