From: Tom Lane <tgl@sss.pgh.pa.us>
To: Marc Cousin <mcousin@sigma.fr>
Cc: pgsql-performance@postgresql.org
Subject: Re: Weird row estimate
Date: Wed, 11 Jul 2007 16:35:31 -0400
Message-ID: <2393.1184186131@sss.pgh.pa.us> (raw)
In-Reply-To: <200707111728.43416.mcousin@sigma.fr>
References: <200707111728.43416.mcousin@sigma.fr>
Marc Cousin <mcousin@sigma.fr> writes:
> Nevertheless, shouldn't the third estimate be smaller or equal to the sum of the two others ?
The planner's estimation for subplan conditions is pretty primitive
compared to joinable conditions. When you add the OR, it's no longer
possible to treat the IN like a join, and everything gets an order of
magnitude dumber :-(
It might be worth trying this as a UNION of the two simple queries.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, mcousin@sigma.fr
Subject: Re: Weird row estimate
In-Reply-To: <2393.1184186131@sss.pgh.pa.us>
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