Re: Effects of GUC settings on automatic replans

Jim Nasby <decibel@decibel.org> writes:
> On Mar 21, 2007, at 5:11 AM, Tom Lane wrote:
>> constraint_exclusion

> Hrm... wasn't that option added in case there was a bug in the  
> exclusion code?

Well, the "bug" was a lack of ways to get rid of plans that were
no longer valid because of constraint changes; a problem that no
longer exists now that the invalidation mechanism is there.
(Hm, I think the docs need some updates now...)

The other argument was that you might not want the costs of searching
for contradictory constraints if your workload was such that the search
never or hardly ever succeeds.  That still justifies the existence of
this GUC variable, I think, but I don't see that it's a reason to force
replanning if the variable is changed.  Certainly it's not any more
interesting than any of the other variables affecting planner behavior.
        regards, tom lane