"Jim Nasby" <[EMAIL PROTECTED]> writes: > On Mar 21, 2007, at 5:11 AM, Tom Lane wrote: >> constraint_exclusion >> >> I'm inclined not to worry about these, since changing them can't affect >> the semantics of the query, at worst its performance. > > Hrm... wasn't that option added in case there was a bug in the exclusion code? > I certainly can't think of any performance reason why you'd want to disable > it... so it might be worth invalidating plans if it changes.
It was added precisely because we didn't have plan invalidation... If you dropped a constraint there was previously nothing to force the plan to be recalculated if it depended on the constraint for correctness. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
