From: Craig Ringer <craig@postnewspapers.com.au>
To: depesz@depesz.com
Cc: sathiya psql <sathiya.psql@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: postgresql is slow with larger table even it is in RAM
Date: Tue, 25 Mar 2008 18:34:35 +0900
Message-ID: <47E8C72B.2010105@postnewspapers.com.au> (raw)
In-Reply-To: <20080325090823.GA5431@depesz.com>
References: <f966c2ee0803250135h57ba1d5bs41f77616ae7186dc@mail.gmail.com>
<20080325090823.GA5431@depesz.com>
hubert depesz lubaczewski wrote:
> On Tue, Mar 25, 2008 at 02:05:20PM +0530, sathiya psql wrote:
>> Any Idea on this ???
>
> yes. dont use count(*).
>
> if you want whole-table row count, use triggers to store the count.
>
> it will be slow. regeardless of whether it's in ram or on hdd.
In other words, if you're having performance problems please provide
EXPLAIN ANALYZE output from a more useful query that does real work,
rather than something like count(*).
COUNT(*) can be slow due to some MVCC limitations; it's been discussed
frequently here so you should search the archives for information.
--
Craig Ringer
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To: pgsql-performance@postgresql.org
Cc: craig@postnewspapers.com.au, depesz@depesz.com, sathiya.psql@gmail.com
Subject: Re: postgresql is slow with larger table even it is in RAM
In-Reply-To: <47E8C72B.2010105@postnewspapers.com.au>
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