From: Steinar H. Gunderson <sgunderson@bigfoot.com>
To: pgsql-performance@postgresql.org
Subject: Re: performance drop on 8.2.4, reverting to 8.1.4
Date: Tue, 5 Jun 2007 23:38:47 +0200
Message-ID: <20070605213847.GA9547@uio.no> (raw)
In-Reply-To: <357fa7590706051430h5db6760dx9d4a46c7a8a36205@mail.gmail.com>
References: <20070518104646.GA13811@uio.no>
<008201c7993c$76c88a10$653e10ac@ilgvaio>
<20070518111455.GA13978@uio.no>
<28604.1179503689@sss.pgh.pa.us>
<357fa7590706051430h5db6760dx9d4a46c7a8a36205@mail.gmail.com>
On Tue, Jun 05, 2007 at 05:30:14PM -0400, Steven Flatt wrote:
> (A) LEFT JOIN (B) ON col WHERE B.col IS NULL
>
> These queries are much slower on 8.2 than on 8.1 for what looks like the
> reason outlined above. I have rewritten a few key queries to be of the
> equivalent form:
>
> (A) WHERE col NOT IN (SELECT col FROM (B))
At least those _can_ be rewritten into a sane form. I have an application
with a large FULL OUTER JOIN, where _both_ sides can return NULLs. (It's
basically a diff between a "current" and a "wanted" state.)
It performs reasonably well under both 8.1 and 8.2, though. Fourteen-table
join or so :-)
/* Steinar */
--
Homepage: http://www.sesse.net/
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To: pgsql-performance@postgresql.org
Cc: sgunderson@bigfoot.com
Subject: Re: performance drop on 8.2.4, reverting to 8.1.4
In-Reply-To: <20070605213847.GA9547@uio.no>
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