| From: | "Sergey Konoplev" <gray(dot)ru(at)gmail(dot)com> |
|---|---|
| To: | "Richard Huxton" <dev(at)archonet(dot)com> |
| Cc: | "pgsql-general(at)postgresql(dot)org >> PG-General Mailing List" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Very slow queries w/ NOT IN preparation (seems like a bug, test case) |
| Date: | 2008-11-11 14:03:44 |
| Message-ID: | c3a7de1f0811110603x1e089e8fh55aefcfec8df32e4@mail.gmail.com |
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| Thread: | |
| Lists: | pgsql-general pgsql-hackers |
> I've never heard of EXPLAIN ANALYSE being *faster* than the actual
> query, it's usually slower due to all the timing calls. The only thing
> it doesn't do is actually send the results over the connection to the
> client. In your case, you're not actually selecting any columns, so that
> can't be it.
>
> Are you sure there's nothing subtly different about the slow query when
> compared with the explain analyse?
>
Sorry, but it seems like you didn't understand the problem.
The thing is that
EXPLAIN (without ANALYZE) ... NOT IN (a lot of values)
works very slow but
EXPLAIN (without ANALYZE) ... IN (a lot of values)
works fast.
Just run the test script I attached.
--
Regards,
Sergey Konoplev
--
PostgreSQL articles in english & russian
http://gray-hemp.blogspot.com/search/label/postgresql/
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