From: Mark Kirkwood <markir@paradise.net.nz>
To: Laurent Manchon <lmanchon@univ-montp2.fr>
Cc: pgsql-performance@postgresql.org
Subject: Re: slow result
Date: Wed, 24 Jan 2007 13:51:51 +1300
Message-ID: <45B6ADA7.80204@paradise.net.nz> (raw)
In-Reply-To: <5.0.2.1.2.20070123133416.00cf43b8@pop.univ-montp2.fr>
References: <5.0.2.1.2.20070123133416.00cf43b8@pop.univ-montp2.fr>
Laurent Manchon wrote:
> Hi,
>
> I have a slow response of my PostgreSQL database 7.4 using this query below
> on a table with 800000 rows:
>
> select count(*)from tbl;
>
> PostgreSQL return result in 28 sec every time.
Can you post the results of:
analyze verbose tbl;
explain analyze select count(*) from tbl;
The first will give us some info about how many pages tbl has (in 7.4
ISTR it does not state the # of dead rows... but anyway), the second
should help us deduce why it is so slow.
Also as others have pointed out, later versions are quite a bit faster
for sequential scans...
Cheers
Mark
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To: pgsql-performance@postgresql.org
Cc: markir@paradise.net.nz, lmanchon@univ-montp2.fr
Subject: Re: slow result
In-Reply-To: <45B6ADA7.80204@paradise.net.nz>
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