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 16:54:18 +0200
Message-ID: <jumcuv$26n$1@dough.gmane.org> (raw)
In-Reply-To: <21308.1343139781@sss.pgh.pa.us>
References: <julsfr$otg$1@dough.gmane.org>
<21308.1343139781@sss.pgh.pa.us>
Tom Lane, 24.07.2012 16:23:
> Thomas Kellerer <spam_eater@gmx.net> writes:
>> DELETE FROM dupes
>> WHERE id NOT IN (SELECT min(b.id)
>> FROM dupes b
>> GROUP BY first_name, last_Name
>> HAVING count(*) > 1);
>
> Doesn't that kill the non-duplicates too?
Ah right - another good point on how important the correct test data is ;)
>> Why does the usage of the CTID column change the plan so drastically?
>
> IIRC, type tid doesn't have any hash support.
>
So the "bad" plan is expected?
Regards
Thomas
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Subject: Re: Using ctid column changes plan drastically
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