From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Alex Johnson <alex(at)aretesystems(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Slow performance with join on many fields |
Date: | 2003-03-04 06:27:42 |
Message-ID: | 20975.1046759262@sss.pgh.pa.us |
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Lists: | pgsql-performance |
Alex Johnson <alex(at)aretesystems(dot)com> writes:
> I'm looking at the following query that joins these three
> tables:
> SELECT ...
> FROM
> (tbl_samples
> INNER JOIN tbl_tests USING ...
> )
> INNER JOIN tbl_results USING ...
You're forcing the join order; perhaps another order is preferable? See
http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit-joins.html
> This is the output from EXPLAIN:
EXPLAIN ANALYZE output would've been more useful (it would have shown
whether a different join order would be better, for one thing).
> I've done the following to try to improve performance:
> increased shared_buffers to 384
That's on the picayune side yet. 1000 buffers or so is where you want
to be, I think. Also, have you run ANALYZE or VACUUM ANALYZE lately?
regards, tom lane
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