From: A. Kretschmer <andreas.kretschmer@schollglas.com>
To: pgsql-sql@postgresql.org
Subject: Re: report generation from table.
Date: Wed, 21 Oct 2009 14:16:08 +0200
Message-ID: <20091021121607.GA1086@a-kretschmer.de> (raw)
In-Reply-To: <f966c2ee0910210452x4a60093ds772b62063e72fe8c@mail.gmail.com>
References: <f966c2ee0910210452x4a60093ds772b62063e72fe8c@mail.gmail.com>
In response to sathiya psql :
> Hi All,
>
> I have been searching for, Preparing report from a huge table.
>
> Queries am executing now are,
> SELECT count(*) from HUGE_TBL where cond1, cond2;
> SELECT count(*) from HUGE_TBL where cond1, cond3;
> --- like this i have different conditions(10-15 different things ) and
> different amount of conditions ( 2 - 5 condition ).
>
> As that is a very huge table, it took time to execute each query ( 2 min ). And
> finally it takes 15 times that ( 30 min ). Is there anyway to do the above
> report efficiently ?
>
> Such executing the query only once, and getting all different outputs required
> ? or fetching result from some cache ?
select sum(case when <cond1> and <cond2> then 1 else 0 end) as query1,
sum(case when <cond1> and <cond3> then 1 else 0 end) as query2, ... from
table;
It forces a whole seq. scan, but only once.
Regards, Andreas
--
Andreas Kretschmer
Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header)
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To: pgsql-sql@postgresql.org
Cc: andreas.kretschmer@schollglas.com
Subject: Re: report generation from table.
In-Reply-To: <20091021121607.GA1086@a-kretschmer.de>
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