From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Kellerer <spam_eater@gmx.net>
Cc: pgsql-performance@postgresql.org
Subject: Re: Using ctid column changes plan drastically
Date: Tue, 24 Jul 2012 11:55:25 -0400
Message-ID: <22819.1343145325@sss.pgh.pa.us> (raw)
In-Reply-To: <jumcuv$26n$1@dough.gmane.org>
References: <julsfr$otg$1@dough.gmane.org>
<21308.1343139781@sss.pgh.pa.us>
<jumcuv$26n$1@dough.gmane.org>
Thomas Kellerer <spam_eater@gmx.net> writes:
> Tom Lane, 24.07.2012 16:23:
>> IIRC, type tid doesn't have any hash support.
> So the "bad" plan is expected?
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.
FWIW, it might be helpful to cast this as a NOT EXISTS rather than
NOT IN subquery.
regards, tom lane
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Subject: Re: Using ctid column changes plan drastically
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