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Re: Optimisation of INTERSECT expressions

From: Bruno Wolff III <bruno(at)wolff(dot)to>
To: Phil Endecott <spam_from_postgresql_lists(at)chezphil(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Optimisation of INTERSECT expressions
Date: 2004-03-23 17:05:00
Message-ID: 20040323170500.GA25181@wolff.to (view raw or flat)
Thread:
Lists: pgsql-performance
On Tue, Mar 23, 2004 at 11:21:39 -0500,
  Phil Endecott <spam_from_postgresql_lists(at)chezphil(dot)org> wrote:
>  Does anyone have any suggestions about how to do this?  I'd like a nice
> general technique that works for all possible subqueries, as my current
> composition with INTERSECT does.

One adjustment you might make is using INTERSECT ALL if you know there
can't be duplicates. Then time won't be wasted trying to remove duplicates.

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