| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, "Jim C(dot) Nasby" <jim(at)nasby(dot)net>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Hints proposal |
| Date: | 2006-10-12 16:24:16 |
| Message-ID: | 11204.1160670256@sss.pgh.pa.us |
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| Lists: | pgsql-hackers pgsql-performance |
Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
> BTW: Do we make use of CHECK constraints in the planner?
Only for "constraint exclusion", and at the moment that's off by default.
The gating problem here is that if the planner relies on a CHECK
constraint, and then you drop the constraint, the previously generated
plan might start to silently deliver wrong answers. So I'd like to see
a plan invalidation mechanism in place before we go very far down the
path of relying on constraints for planning. That's something I'm going
to try to make happen for 8.3, though.
regards, tom lane
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