On Sat, Apr 6, 2013 at 9:27 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Franck Routier <franck.rout...@axege.com> writes: > > Le 05/04/2013 16:17, Tom Lane a écrit : > >> What have you got the statistics targets set to in this database? > > > Ok, the problem definitely comes from the default_statistics_target > > which is obviously too high on the database. > > Yeah, eqjoinsel() is O(N^2) in the lengths of the MCV lists, in the > worst case where there's little overlap in the list memberships. > The actual cost would depend a lot on the specific column datatypes. >
I guess this pre-emptively answers a question I was intending to ask on performance: Whether anyone increased default_statistics_target and came to regret it. I had seen several problems fixed by increasing default_statistics_target, but this is the first one I recall caused by increasing it. Do you think fixing the O(N^2) behavior would be a good to-do item? Cheers, Jeff
