From: Shoaib Mir <shoaibmir@gmail.com>
To: A. Kretschmer <andreas.kretschmer@schollglas.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: count * performance issue
Date: Thu, 6 Mar 2008 17:15:06 +1100
Message-ID: <bf54be870803052215y5bb56235k5ea05ada1d701022@mail.gmail.com> (raw)
In-Reply-To: <20080306060829.GA21084@a-kretschmer.de>
References: <f966c2ee0803052142l6a105678jfe2da92a0d9371@mail.gmail.com>
<f966c2ee0803052143k4570d771o6c300647d3b987d@mail.gmail.com>
<20080306060829.GA21084@a-kretschmer.de>
On Thu, Mar 6, 2008 at 5:08 PM, A. Kretschmer <
andreas.kretschmer@schollglas.com> wrote:>
> > am having a table with nearly 50 lakh records,
> >
> > it has more than 15 columns, i want to count how many records are there,
> it is
> > taking nearly 17 seconds to do that...
> >
> > i know that to get a approximate count we can use
> > SELECT reltuples FROM pg_class where relname = TABLENAME;
> >
> > but this give approximate count, and i require exact count...
>
> There aren't a general solution. If you realy need the exact count of
> tuples than you can play with a TRIGGER and increase/decrease the
> tuple-count for this table in an extra table.
>
>
>
Or do something like:
ANALYZE tablename;
select reltuple from pg_class where relname = 'tablename';
That will also return the total number of rows in a table and I guess might
be much faster then doing a count(*) but yes if trigger can be an option
that can be the easiest way to do it and fastest too.
--
Shoaib Mir
Fujitsu Australia Software Technology
shoaibm[@]fast.fujitsu.com.au
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To: pgsql-performance@postgresql.org
Cc: shoaibmir@gmail.com, andreas.kretschmer@schollglas.com
Subject: Re: count * performance issue
In-Reply-To: <bf54be870803052215y5bb56235k5ea05ada1d701022@mail.gmail.com>
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