From: A. Kretschmer <andreas.kretschmer@schollglas.com>
To: pgsql-sql@postgresql.org
Subject: Re: short-cutting if sum()>constant
Date: Tue, 22 Dec 2009 15:12:31 +0100
Message-ID: <20091222141231.GE10308@a-kretschmer.de> (raw)
In-Reply-To: <20091222133527.3007bd96@dawn.webthatworks.it>
References: <20091222133527.3007bd96@dawn.webthatworks.it>
In response to Ivan Sergio Borgonovo :
> Hi,
>
> I'd like to know if
>
> select sum(qty) from t where status=37;
>
> is > constant.
>
> qty is always >0.
>
> Is there a way to skip examining further rows and return a result
> ASAP?
I think no.
But you can create a new table with 2 columns: status (primary key) and
a column for the sum of qty. And you need a TRIGGER: update this table
for every insert, update and delete on your table t.
Now you can ask _this_ new table if the sum(qty) > your constant, this
should work very fast.
Just an idea...
Andreas
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Andreas Kretschmer
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To: pgsql-sql@postgresql.org
Cc: andreas.kretschmer@schollglas.com
Subject: Re: short-cutting if sum()>constant
In-Reply-To: <20091222141231.GE10308@a-kretschmer.de>
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