From: | Paul Thomas <paul(at)tmsl(dot)demon(dot)co(dot)uk> |
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To: | Fabian Kreitner <fabian(dot)kreitner(at)ainea-ag(dot)de> |
Cc: | "pgsql-performance (at) postgresql (dot) org" <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: index / sequential scan problem |
Date: | 2003-07-17 12:34:45 |
Message-ID: | 20030717133445.A27991@bacon |
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Thread: | |
Lists: | pgsql-performance |
On 17/07/2003 12:13 Fabian Kreitner wrote:
> That is what I read too and is why Im confused that the index is indeed
> executing faster. Can this be a problem with the hardware and/or
> postgress installation?
It's more likely that the OS has most of the data cached after the first
query and so doesn't need to re-read that data from disk when you retry
the query with seq scan disabled. Try something like this:
set enable_seqscan to true;
explain analyze ......
set enable_seqscan to false;
explain analyze ......
set enable_seqscan to true;
explain analyze ......
I expect you will find that the third query is also a lot faster that the
first query.
HTH
--
Paul Thomas
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