From: Richard Huxton <dev@archonet.com>
To: Siva Kumar <tech@leatherlink.net>
To: pgsql-general@postgresql.org
Subject: Re: Query optimization
Date: Fri, 4 Oct 2002 14:29:51 +0100
Message-ID: <200210041429.51956.dev@archonet.com> (raw)
In-Reply-To: <200210041756.35489.tech@leatherlink.net>
References: <200210041347.55055.tech@leatherlink.net>
<200210041114.17241.dev@archonet.com>
<200210041756.35489.tech@leatherlink.net>
On Friday 04 Oct 2002 1:26 pm, Siva Kumar wrote:
> Giving below the output of EXPLAIN ANALYSE. I could not make much sense out
> of it, please help!
Scary aren't they ;-)
The important thing is you've got plenty of "Index Scan"s rather than Seq
Scans. The other point is the final time:
> Total runtime: 5.45 msec
Now, since that's not what you're getting, I'd think Neil (see other reply) is
right and you need to look at issuing "SET geqo = off;" before the query.
Postgresql has a genetic algorithm that kicks in on what it thinks is a very
complex query, this can take a long time to analyse the options available but
pays dividends on a big query. In your case you're only getting a few rows
and so it takes longer to analyse than to get the results.
The other thing that might work is rewriting the query with explicit JOINs - I
think that should make it clear to Postgresql what order to do things in.
- Richard Huxton
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To: pgsql-general@postgresql.org
Cc: dev@archonet.com, tech@leatherlink.net
Subject: Re: Query optimization
In-Reply-To: <200210041429.51956.dev@archonet.com>
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