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From: Ivan Voras <ivoras@geri.cc.fer.hr>
To: pgsql-performance@postgresql.org
Subject: Re: what is the maximum number of rows in a table in postgresql 8.1
Date: Tue, 25 Mar 2008 14:16:43 +0100
Message-ID: <fsatvr$poa$1@ger.gmane.org> (raw)
In-Reply-To: <f966c2ee0803250550o563309a3p2c2d4509535c8bf6@mail.gmail.com>
References: <f966c2ee0803250442g9ceaf61v2c3f35221fcc6481@mail.gmail.com>
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	<f966c2ee0803250454k716edf4cgcd054e7b563e530c@mail.gmail.com>
	<20080325120101.GC6756@alvh.no-ip.org>
	<f966c2ee0803250508t444524b6y44b9ee67c8e04673@mail.gmail.com>
	<47E8EEF1.40709@postnewspapers.com.au>
	<f966c2ee0803250550o563309a3p2c2d4509535c8bf6@mail.gmail.com>

sathiya psql wrote:
> EXPLAIN ANALYZE SELECT count(*) from call_log_in_ram ;
>                                                             QUERY
> PLAN                                                        
> ------------------------------------
> ----------------------------------------------------------------------------------------------
>  Aggregate  (cost=90760.80..90760.80 rows=1 width=0) (actual
> time=6069.373..6069.374 rows=1 loops=1)
>    ->  Seq Scan on call_log_in_ram  (cost=0.00..89121.24 rows=3279119
> width=0) (actual time=0.012..4322.345 rows=3279119 loops=1)
>  Total runtime: 6069.553 ms
> (3 rows)

You will never get good performance automatically with COUNT(*) in
PostgreSQL. You can either create your own infrastructure (triggers,
statistics tables, etc) or use an approximate result like this:

CREATE OR REPLACE FUNCTION fcount(varchar) RETURNS bigint AS $$
        SELECT reltuples::bigint FROM pg_class WHERE relname=$1;
$$ LANGUAGE 'sql';


Use the above function as:

SELECT fcount('table_name');
 fcount
--------
   7412
(1 row)




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