Re: Possible causes of sometimes slow single-row UPDATE with trivial indexed condition?

From: Andy Colson <andy(at)squeakycode(dot)net>
To: Vlad Romascanu <vromascanu(at)monaqasat(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Possible causes of sometimes slow single-row UPDATE with trivial indexed condition?
Date: 2009-09-17 13:45:43
Message-ID: 4AB23D87.80707@squeakycode.net
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Vlad Romascanu wrote:
> Problem occurs when running (in production) Postgres 8.3.7 64-bit (from
> RPM) on Ubuntu 8.04.2, on an Amazon EC2 (xen) "Large" instance (8GB
> RAM), with the DB on a 50GB EC2 block device.
> Problem does not occur when running (in staging/pre-production) Postgres
> 8.3.5 32-bit (from RPM) on Ubuntu 8.04.1, on a less beefy Amazon EC2
> (xen) "Small" instance, with the DB on a 5GB EC2 block device.
>
> I am running with slow query logging on, and somewhat inexplicably I've
> been getting the following slow UPDATE query several times in the past
> weeks (I'm also including some context lines above and below):
>

I'm not sure how Amazon vm's work, but are there multiple vm's on one
box? Just because your vm has zero cpu/disk does not mean the host
isn't pegged out of its mind.

Does Amazon give any sort of host stats?

-Andy

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