From: Andreas Kretschmer <akretschmer@spamfence.net>
To: pgsql-performance@postgresql.org
Subject: Re: UNION and bad performance
Date: Sat, 11 Dec 2010 14:45:47 +0100
Message-ID: <20101211134547.GB12385@tux> (raw)
In-Reply-To: <C4DAC901169B624F933534A26ED7DF31034BB99A@JENMAIL01.ad.intershop.net>
References: <4D00B4DE.3030508@xgs-france.com>
<C4DAC901169B624F933534A26ED7DF31034BB99A@JENMAIL01.ad.intershop.net>
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
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect. (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly." (unknown)
Kaufbach, Saxony, Germany, Europe. N 51.05082°, E 13.56889°
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To: pgsql-performance@postgresql.org
Cc: akretschmer@spamfence.net
Subject: Re: UNION and bad performance
In-Reply-To: <20101211134547.GB12385@tux>
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