From: Thomas Kellerer <spam_eater@gmx.net>
To: pgsql-performance@postgresql.org
Subject: Re: Using ctid column changes plan drastically
Date: Tue, 24 Jul 2012 18:32:09 +0200
Message-ID: <jumim1$nq7$1@dough.gmane.org> (raw)
In-Reply-To: <22819.1343145325@sss.pgh.pa.us>
References: <julsfr$otg$1@dough.gmane.org>
<21308.1343139781@sss.pgh.pa.us>
<jumcuv$26n$1@dough.gmane.org>
<22819.1343145325@sss.pgh.pa.us>
Tom Lane wrote on 24.07.2012 17:55:
> Joins on tid columns just aren't supported very well at the moment.
> Partly that's from lack of round tuits, and partly it's because it
> doesn't seem all that wise to encourage people to use them. There
> are gotchas if any of the rows receive concurrent updates.
Thanks for the clarification. I will keep that in mind.
> FWIW, it might be helpful to cast this as a NOT EXISTS rather than
> NOT IN subquery.
Hmm. How would you change that into an NOT EXISTS clause (so that one of the duplicates remains)
Everything I come up with is in fact slower than the NOT IN solution.
Regards
Thomas
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Subject: Re: Using ctid column changes plan drastically
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