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Message-ID: <4FF6C90B.8070402@ringerc.id.au>
Date: Fri, 06 Jul 2012 19:16:27 +0800
From: Craig Ringer <ringerc@ringerc.id.au>
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To: Yan Chunlu <springrider@gmail.com>
CC: pgsql-performance@postgresql.org
Subject: Re: how could select id=xx so slow?
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On 07/06/2012 02:17 PM, Yan Chunlu wrote:

> so I wonder could this simple select is innocent and affected badly by 
> other queries? how could I find those queries that really slow down 
> the database?

It might not be other queries. Your query could be taking that long 
because it was blocked by a lock during maintenance work (say, an ALTER 
TABLE). It's also quite possible that it was held up by a slow 
checkpoint; check your logs to see if there are warnings about 
checkpoint activity.

--
Craig Ringer