Date: Sat, 11 Dec 2010 14:45:47 +0100
From: Andreas Kretschmer <akretschmer@spamfence.net>
To: pgsql-performance@postgresql.org
Subject: Re: UNION and bad performance
Message-ID: <20101211134547.GB12385@tux>
References: <4D00B4DE.3030508@xgs-france.com>
	<C4DAC901169B624F933534A26ED7DF31034BB99A@JENMAIL01.ad.intershop.net>
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Marc Mamin <M.Mamin@intershop.de> wrote:

> Hello,
> 
>  
> 
> UNION will remove all duplicates, so that the result additionally requires to
> be sorted.

Right, to avoid the SORT and UNIQUE - operation you can use UNION ALL


> 
> Anyway,  for performance issues, you should always start investigation with
> explain analyze .

ACK.

    Arguments to support bottom-posting...

    A: Because we read from top to bottom, left to right.
    Q: Why should I start my reply below the quoted text?

    A: Because it messes up the order in which people normally read text.
    Q: Why is top-posting such a bad thing?

    A: The lost context.
    Q: What makes top-posted replies harder to read than bottom-posted?

    A: Yes.
    Q: Should I trim down the quoted part of an email to which I'm replying?


Andreas
-- 
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"If I was god, I would recompile penguin with --enable-fly."   (unknown)
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