Re: poor performance of db?

From: PFC <lists(at)boutiquenumerique(dot)com>
To: SpaceBallOne <space_ball_one(at)hotmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: poor performance of db?
Date: 2005-01-26 20:02:42
Message-ID: opsk77as1gth1vuj@musicbox
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> Every time I tested an idea to speed it up, I got exactly the same
> loading time on a Athlon 1800+, 256Mb RAM, 20Gb PATA computer as
> compared to a Dual Opteron 246, 1Gb RAM, 70Gb WD Raptor SATA server.
> Now, why a dual opteron machine can't perform any faster than a lowly
> 1800+ athlon in numerous tests is completely beyond me ... increased
> memory and RAID 0 disc configurations so far have not resulted in any
> significant performance gain in the opteron server.

How many rows does the query return ?

Maybe a lot of time is spent, hidden in the PHP libraries, converting the
rows returned by psql into PHP objects.

You should try that :

EXPLAIN ANALYZE SELECT your query
-> time is T1

CREATE TABLE cache AS SELECT your query
EXPLAIN ANALYZE SELECT * FROM cache
-> time is T2 (probably very small)

Now in your PHP script replace SELECT your query by SELECT * FROM cache.
How much does the final page time changes ? This will tell you the time
spend in the postgres engine, not in data transmission and PHPing. It will
tell wat you can gain optimizing the query.

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