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Re: Queries sometimes take 1000 times the normal time

From: "Anders K(dot) Pedersen" <akp(at)cohaesio(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Queries sometimes take 1000 times the normal time
Date: 2003-08-28 18:57:02
Message-ID: bilj9u$a49$1@harrier.cohaesio.com (view raw or flat)
Thread:
Lists: pgsql-performance
Rod Taylor wrote:
>>With regards to other jobs on the server, there is a MySQL server on it 
>>as well, which from time to time has some multi-second queries generated 
>>from a webserver also on this host, but the MySQL is running with nice 
>>10 (PostgreSQL isn't nice'd).
> 
> Do those MySQL queries hit disk hard?

I guess they may be able to do so - the MySQL database is 450 MB, and 
the server has 512 MB RAM, and some of the queries pretty summarizes 
everything in the database.

However, I just cross-referenced the access logs from the webserver with 
the duration logs, and although some of the spikes did happen, while 
there would have been some MySQL activity (I can't tell for sure, if it 
was simple queries or the long ones), other spikes happened without any 
website activity in the surrounding minutes.

> I've never seen PostgreSQL have hicups like you describe when running on
> a machine by itself.  I have experienced similar issues when another
> process (cron job in my case) caused brief swapping to occur.

OK. I may have to try to put the database on a separate server.

Regards,
Anders K. Pedersen


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