On Thursday 16 July 2009 19:13:55 Robert Haas wrote: > On Thu, Jul 16, 2009 at 12:49 PM, Andres Freund<and...@anarazel.de> wrote: > > On Thursday 16 July 2009 17:59:58 Tom Lane wrote: > >> Andres Freund <and...@anarazel.de> writes: > >> > The default settings currently make it relatively hard to trigger geqo > >> > at all. > >> > >> Yes, and that was intentional. One of the implications of what we're > >> discussing here is that geqo would get used a lot more for "typical > >> complex queries" (if there is any such thing as a typical one). So > >> it's fully to be expected that the fallout would be pressure to improve > >> geqo in various ways. > >> > >> Given that we are at the start of the development cycle, that prospect > >> doesn't scare me --- there's plenty of time to fix whatever needs > >> fixing. However, I am leaning to the feeling that I don't want to be > >> putting people in a position where they have no alternative but to use > >> geqo. So adjusting rather than removing the collapse limits is seeming > >> like a good idea. > > > > Hm. I see a, a bit more fundamental problem with geqo: > > I tried several queries, and I found not a single one, where the whole > > genetical process did any significant improvments to the 'worth'. > > It seems that always the best variant out of the pool is either the path > > choosen in the end, or at least the cost difference is _really_ low. > Ouch. Did you insert some debugging code to get that information, or > how did you come to that conclusion? Yes, I enabled GEQO_DEBUG and added some more debugging output.
Btw, a higher generation count does not change that. Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
