Re: vacuum, performance, and MVCC

From: "Jochem van Dieten" <jochemd(at)gmail(dot)com>
To: "Mark Woodward" <pgsql(at)mohawksoft(dot)com>
Cc: "Hannu Krosing" <hannu(at)skype(dot)net>, "Christopher Browne" <cbbrowne(at)acm(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: vacuum, performance, and MVCC
Date: 2006-06-22 16:53:07
Message-ID: f96a9b830606220953i6369796hf18e3631a718068a@mail.gmail.com
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On 6/22/06, Mark Woodward wrote:
(..)
> thousand active sessions
(..)
> If an active user causes a session update once a second
(..)
> Generally speaking, sessions aren't updated when they change, they are
> usually updated per HTTP request. The data in a session may not change,
> but the session handling code doesn't know this and simply updates anyway.

So what you are saying is that you are doing hundreds of unnecessary
updates per second and as a result of those unnecessary problems you
have a performance problem. Why not attack the root of the problem and
make the session handler smarter? And if you can't do that, put some
logic in the session table that turns an update without changes into a
no-op?

Jochem

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