| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, Martin Lesser <ml-pgsql(at)bettercom(dot)de> |
| Subject: | Re: "Constraint exclusion" is not general enough |
| Date: | 2006-08-04 21:54:35 |
| Message-ID: | 18043.1154728475@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
"Jim C. Nasby" <jnasby(at)pervasive(dot)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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