> On 30 Dec 2015, at 10:16, David Rowley <david.rowley@2ndquadrant.com> wrote: > > A number of ideas were suggested on the other thread about how we might go about solving this problem. In [3] Simon talked about perhaps enabling extra optimisations when the planner sees that the plan will cost more than some given threshold. That's perhaps an option, but may not work well for optimisations which must take place very early in planning, for example [4]. > Another idea which came up was from Evgeniy [5], which was more of a request not to do it this way, but never-the-less, the idea was basically to add lots of GUCs to enable/disable each extra planner feature. >
Well, my idea was to track planning/execution cost in something like pg_stat_statements. That way we can track actual time, not estimated cost like Simon proposed.
I like this idea also, but I do see the use for this as more of a guide which could be used by the DBA to tweak some sort of planner_effort GUCs. I don't think that the data of pg_stat_statements could be used by the planner as this is an extension rather than core code.
