From: | Herbert Liechti <Herbert(dot)Liechti(at)thinx(dot)ch> |
---|---|
To: | pgsql-general(at)postgreSQL(dot)org |
Cc: | Mel Wilson <mwilson(at)the-wire(dot)com> |
Subject: | Re: [GENERAL] Trouble: subquery doesn't terminate |
Date: | 2000-01-26 07:27:25 |
Message-ID: | 388EA1DD.6685C433@thinx.ch |
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Lists: | pgsql-general |
Mel Wilson wrote:
>
> Trouble: I'm running CGI perl routines from Apache (without
> mod_perl) to query a small database. This query ran over 6 minutes
> before Apache timed out and dropped the pipe:
>
> $result = $conn->exec(qq/
> SELECT t.tune_id, t.title
> FROM tune t
> WHERE t.tune_id IN
> (SELECT c.tune_id FROM composer c WHERE c.person_id = $person_id)
> /);
The IN Clause is known to be very slow. Try to use the EXISTS clause
instead. I had the same problem. After changing to the EXISTS
variant my performance troubles went away.
--
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Herbert Liechti E-Mail: Herbert(dot)Liechti(at)thinx(dot)ch
ThinX networked business services Stahlrain 10, CH-5200 Brugg
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