Re: Why is restored database faster?

From: Neil Conway <neilc(at)samurai(dot)com>
To: "david(at)shadovitz(dot)com" <david(at)shadovitz(dot)com>
Cc: "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Why is restored database faster?
Date: 2003-12-17 06:00:13
Message-ID: 87iskgugpe.fsf@mailbox.samurai.com
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David Shadovitz <david(at)shadovitz(dot)com> writes:
> What could account for this difference?

Lots of things -- disk fragmentation, expired tuples that aren't being
cleaned up by VACUUM due to a long-lived transaction, the state of the
kernel buffer cache, the configuration of the kernel, etc.

> How can I get the original server to perform as well as the new one?

Well, you can start by giving us some more information. For example,
what is the output of VACUUM VERBOSE on the slow server? How much disk
space does the database directory take up on both machines?

(BTW, "SELECT count(*) FROM table" isn't a particularly good DBMS
performance indication...)

-Neil

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