On Wed, Jul 08, 2009 at 04:13:11PM -0500, Kevin Grittner wrote: > Tom Lane <t...@sss.pgh.pa.us> wrote: > > > It occurs to me that one way to make GEQO less scary would be to > > take out the nondeterminism by resetting its random number generator > > for each query. You might get a good plan or an awful one, but at > > least it'd be the same one each time. DBAs like predictability. > > +1 The biggest reason that I've tended to avoid geqo is that I would > never know when it might do something really stupid with a query one > time out of some large number, leading to mysterious complaints which > could eat a lot of time. > > For a moment it seemed logical to suggest a session GUC for the seed, > so if you got a bad plan you could keep rolling the dice until you got > one you liked; but my right-brain kept sending shivers down my spine > to suggest just how uncomfortable it was with that idea.... > > -Kevin >
+1 I like the idea of a session GUC for the random number seed. If we can come up with a way to prune the search space more aggressively, GECO (or GECO2) will be much less prone to generating a bad plan. I also think that a session variable would make it easier to test GECO* by removing the nondeteminism. Ken -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
