Re: "Constraint exclusion" is not general enough - Mailing list pgsql-hackers

From Tom Lane
Subject Re: "Constraint exclusion" is not general enough
Date
Msg-id 18043.1154728475@sss.pgh.pa.us
Whole thread Raw
In response to Re: "Constraint exclusion" is not general enough  ("Jim C. Nasby" <jnasby@pervasive.com>)
Responses Re: "Constraint exclusion" is not general enough
List pgsql-hackers
"Jim C. Nasby" <jnasby@pervasive.com> writes:
> On Fri, Aug 04, 2006 at 02:40:30PM -0400, Tom Lane wrote:
>> I would argue that turning on constraint_exclusion ought to instruct
>> the planner to catch this sort of thing, whereas when it's off we
>> ought not expend the cycles.  I have a preliminary patch (below)
>> that seems to fix it.

> How many cycles are we talking about here? Is it even worth the GUC?

I think so.  On simple queries the optimization will *never* fire,
and there's no point in doing the search.  People who are running
complex queries will want to turn it on, but the mysql-equivalent
crew will just find it a waste of cycles.
        regards, tom lane


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