On Tue, 2008-05-27 at 17:43 -0400, Tom Lane wrote: > Simon Riggs <simon@xxxxxxxxxxxxxxx> writes: > > I have a complex query where making a small change to the SQL increases > > run-time by > 1000 times. > > > The first SQL statement is of the form > > > A JOIN B ON (a.id = b.id) LEFT JOIN C ON (a.id = c.id) > > > and the second is like this > > > A JOIN B ON (a.id = b.id) LEFT JOIN C ON (b.id = c.id) > > > the only difference is the substitution of a -> b > > Please provide an actual test case. Getting closer, but still not able to produce a moveable test case. Symptoms are * using partitioning * when none of the partitions are excluded * when equivalence classes ought to be able to reconcile join Still working on it -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support
