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Re: SLOW query with aggregates

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "A Palmblad" <adampalmblad(at)yahoo(dot)ca>
Cc: "Postgres Performance" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: SLOW query with aggregates
Date: 2004-03-23 20:32:08
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
"A Palmblad" <adampalmblad(at)yahoo(dot)ca> writes:
>  GroupAggregate  (cost=0.00..338300.34 rows=884 width=345) (actual
> time=86943.272..382718.104 rows=3117 loops=1)
>    ->  Merge Join  (cost=0.00..93642.52 rows=1135610 width=345) (actual
> time=0.148..24006.748 rows=1120974 loops=1)

You do not have a planning problem here, and trying to change the plan
is a waste of time.  The slowness is in the actual computation of the
aggregate functions; ergo the only way to speed it up is to change what
you're computing.  What aggregates are you computing exactly, and over
what datatypes?

			regards, tom lane

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