From: Anne Rosset <arosset@collab.net>
To: Jochen Erwied <jochen@pgsql-performance.erwied.eu>
Cc: pgsql-performance@postgresql.org
Subject: Re: Need to increase performance of a query
Date: Thu, 10 Jun 2010 12:44:54 -0700
Message-ID: <4C1140B6.5020803@collab.net> (raw)
In-Reply-To: <10510424234.20100610213924@erwied.eu>
References: <4C1125F0.8090101@collab.net>
<4C112B19.6080908@krogh.cc>
<4C113098.5040105@collab.net>
<98414706.20100610212211@erwied.eu>
<4C113E2F.6000305@collab.net>
<10510424234.20100610213924@erwied.eu>
Jochen Erwied wrote:
> Thursday, June 10, 2010, 9:34:07 PM you wrote:
>
>
>> Time: 1.516 ms
>>
>
>
>> Time: 13.177 ms
>>
>
> I'd suppose the first query to scan a lot less rows than the second one.
> Could you supply an explained plan for the fast query?
>
>
Hi Jochen,
Here is the explained plan for the fastest query:
psrdb=# explain analyze ELECT
psrdb-# MAX(item_rank.rank) AS maxRank
psrdb-# FROM
psrdb-# item_rank item_rank
psrdb-# WHERE
psrdb-# item_rank.pf_id='plan1408';
ERROR: syntax error at or near "ELECT" at character 17
psrdb=# explain analyze SELECT
psrdb-# MAX(item_rank.rank) AS maxRank
psrdb-# FROM
psrdb-# item_rank item_rank
psrdb-# WHERE
psrdb-# item_rank.pf_id='plan1408';
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------
Aggregate (cost=8.28..8.29 rows=1 width=8) (actual time=0.708..0.709
rows=1 loops=1)
-> Index Scan using item_rank_pf on item_rank (cost=0.00..8.27
rows=1 width=8) (actual time=0.052..0.407 rows=303 loops=1)
Index Cond: ((pf_id)::text = 'plan1408'::text)
Total runtime: 0.761 ms
(4 rows)
Time: 2.140 ms
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To: pgsql-performance@postgresql.org
Cc: arosset@collab.net, jochen@pgsql-performance.erwied.eu
Subject: Re: Need to increase performance of a query
In-Reply-To: <4C1140B6.5020803@collab.net>
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