Re: Speeding up select distinct

From: Greg Stark <gsstark(at)mit(dot)edu>
To: Laurent Martelli <laurent(at)aopsys(dot)com>
Cc: PFC <lists(at)boutiquenumerique(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Speeding up select distinct
Date: 2005-03-17 02:29:13
Message-ID: 87ekefj98m.fsf@stark.xeocode.com
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Laurent Martelli <laurent(at)aopsys(dot)com> writes:

> PFC> SELECT owner from pictures group by owner;
>
> That's a slight improvement, but there's still a seq scan on pictures:

It should be a sequential scan. An index will be slower.

> HashAggregate (cost=114.38..114.38 rows=21 width=4) (actual time=7.585..7.605 rows=21 loops=1)
> -> Seq Scan on pictures (cost=0.00..103.70 rows=4270 width=4) (actual time=0.015..3.272 rows=4270 loops=1)
> Total runtime: 7.719 ms

That's the best plan for this query.

--
greg

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