On Thu, Jan 12, 2006 at 09:48:41AM +0000, Simon Riggs wrote: > On Wed, 2006-01-11 at 22:23 -0500, Tom Lane wrote: > > =?iso-8859-1?Q?Jean-Philippe_C=F4t=E9?= <jean-philippe.cote@xxxxxxxxxxxxxxxx> writes: > > > Thanks a lot for this info, I was indeed exceeding the genetic > > > optimizer's threshold. Now that it is turned off, I get > > > a very stable response time of 435ms (more or less 5ms) for > > > the same query. It is about three times slower than the best > > > I got with the genetic optimizer on, but the overall average > > > is much lower. > > > > Hmm. It would be interesting to use EXPLAIN ANALYZE to confirm that the > > plan found this way is the same as the best plan found by GEQO, and > > the extra couple hundred msec is the price you pay for the exhaustive > > plan search. If GEQO is managing to find a plan better than the regular > > planner then we need to look into why ... > > It seems worth noting in the EXPLAIN whether GEQO has been used to find > the plan, possibly along with other factors influencing the plan such as > enable_* settings. > Is it the plan that is different in the fastest case with GEQO or is it the time needed to plan that is causing the GEQO to beat the exhaustive search? Ken
