From: Markus Schaber <schabi@logix-tt.com>
To: Stefano Dal Pra <s.dalpra@gmail.com>
Cc: pgsql-sql@postgresql.org
Cc: pgsql-performance@postgresql.org
Subject: Re: [SQL] two queryes in a single tablescan
Date: Sat, 20 Oct 2007 12:58:24 +0200
Message-ID: <20071020125824.75df357c@kingfisher.sec.intern.logix-tt.com> (raw)
In-Reply-To: <290a5abc0710170530v215cb2b0q4fa000ad43096a28@mail.gmail.com>
References: <290a5abc0710170530v215cb2b0q4fa000ad43096a28@mail.gmail.com>
Hi, Stefano,
"Stefano Dal Pra" <s.dalpra@gmail.com> wrote:
> suppose you have a large table tab and two (or more) queryes like this:
>
> SELECT count(*),A FROM tab WHERE C GROUP BY A;
> SELECT count(*),B FROM tab WHERE C GROUP BY B;
>
> is there any way to get both results in a single query,
> eventually through stored procedure?
> The retrieved [count(*),A] ; [count(*),B)] data couldnt fit
> on a single table, of course.
>
> The main goal would be to get multiple results while scanning the
> table[s] once only
> thus getting results in a faster way.
PostgreSQL 8.3 contains great improvements in this area, you can simply
start the selects from concurrent connections, and the backend will
synchronize the scans.
Regards,
Markus
--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
Fight against software patents in Europe! www.ffii.org
www.nosoftwarepatents.org
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To: pgsql-sql@postgresql.org
Cc: schabi@logix-tt.com, s.dalpra@gmail.com, pgsql-performance@postgresql.org
Subject: Re: [SQL] two queryes in a single tablescan
In-Reply-To: <20071020125824.75df357c@kingfisher.sec.intern.logix-tt.com>
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