Date: Sat, 6 Nov 2010 16:53:54 +0000
From: David W Noon <dwnoon@ntlworld.com>
To: pgsql-admin@postgresql.org
Subject: Re: Interesting Query Performance Question
Message-ID: <20101106165354.67ed9532@karnak.local>
In-Reply-To: <20024.1289059188@sss.pgh.pa.us>
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On Sat, 06 Nov 2010 11:59:48 -0400, Tom Lane wrote about Re: [ADMIN]
Interesting Query Performance Question:

>In general, NOT IN is hard to optimize because of its weird behavior
>for NULLs.  I'd suggest looking into converting the query to use an
>EXISTS instead.

I have know about that issue for some years, so I always use a column
that has been declared NOT NULL for the sub-query.  Does PostgreSQL not
use that property to bypass the vagaries of NULL in an IN predicate?
--=20
Regards,

Dave  [RLU #314465]
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dwnoon@ntlworld.com (David W Noon)
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