Jeff Janes <jeff.janes@xxxxxxxxx> writes: > On Sat, Apr 6, 2013 at 9:27 AM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: >> 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. > 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. I recall having heard some similar complaints before, but not often. > Do you think fixing the O(N^2) behavior would be a good to-do item? If you can think of a way to do it that doesn't create new assumptions that eqjoinsel ought not make (say, that the datatype is sortable). I guess one possibility is to have a different join selectivity function for those types that *are* sortable, which would fix the issue for most commonly used types. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
