| From: | "John Hansen" <john(at)geeknet(dot)com(dot)au> |
|---|---|
| To: | "Bruno Wolff III" <bruno(at)wolff(dot)to> |
| Cc: | "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Alvaro Herrera" <alvherre(at)surnet(dot)cl>, "Josh Berkus" <josh(at)agliodbs(dot)com>, <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: query plan ignoring check constraints |
| Date: | 2005-06-21 11:54:34 |
| Message-ID: | 5066E5A966339E42AA04BA10BA706AE50A9364@rodrick.geeknet.com.au |
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| Lists: | pgsql-hackers |
Bruno Wolff III [mailto:bruno(at)wolff(dot)to] Wrote
> I think the real problem is that check constraints on tables
> aren't used by the optimizer. Given that, what you have below
> is expected.
> There has been talk about that in the past, but I haven't
> heard anything recently about someone considering implenting that.
>
> For your problem consider not using a partial index. It isn't
> going to save anything if it has a constraint matching that
> of the table.
Ahh, I get it now,...
If a column has a CHECK (col IN (1,2,3)) and a query says .. WHERE col
= 4; then the planner should
know that the query will return 0 rows, right?
... John
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