Cc: pgsql-performance@postgresql.org
Message-Id: <AE4F81FF-C8BE-44BC-A79D-48EC5BF20162@socket.ch>
From: Thomas Spreng <spreng@socket.ch>
To: PFC <lists@peufeu.com>
In-Reply-To: <op.t9odybcgcigqcu@apollo13.peufeu.com>
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Subject: Re: Oddly slow queries
Date: Wed, 16 Apr 2008 06:07:04 +0200
References: <3D7728ED-3D36-47E6-9266-351073ED4E11@socket.ch>
	<op.t9odybcgcigqcu@apollo13.peufeu.com>


On 16.04.2008, at 01:24, PFC wrote:
>
>> The queries in question (select's) occasionally take up to 5 mins  
>> even if they take ~2-3 sec under "normal" conditions, there are no  
>> sequencial scans done in those queries. There are not many users  
>> connected (around 3, maybe) to this database usually since it's  
>> still in a testing phase. I tried to hunt down the problem by  
>> playing around with resource usage cfg options but it didn't really  
>> made a difference.
>
> 	Could that be caused by a CHECKPOINT ?


actually there are a few log (around 12 per day) entries concerning  
checkpoints:

LOG:  checkpoints are occurring too frequently (10 seconds apart)
HINT:  Consider increasing the configuration parameter  
"checkpoint_segments".

But wouldn't that only affect write performance? The main problems I'm  
concerned about affect SELECT queries.

Regards,

Tom


PS: WAL settings are all set to defaults.