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To: PFC <lists@boutiquenumerique.com>
Cc: _moray <moray1.geo@yahoo.com>, pgsql-sql@postgresql.org
Subject: Re: a very big table 
In-reply-to: <op.son5avzcth1vuj@localhost> 
References: <lkf2e.2987$aH3.649@news.edisontel.com>
	<op.son5avzcth1vuj@localhost>
Comments: In-reply-to PFC <lists@boutiquenumerique.com>
	message dated "Sun, 03 Apr 2005 20:21:57 +0200"
Date: Sun, 03 Apr 2005 20:50:12 -0400
Message-ID: <13636.1112575812@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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PFC <lists@boutiquenumerique.com> writes:
> 	Here you don't need to LEFT JOIN, you can use a straight simple  
> unconstrained join because the rows generated by the LEFT JOINs which have  
> NULL in the right columns will be rejected by the WHERE clause anyway :

In recent versions of Postgres, the planner knows this and can make the
simplification for itself, at least if the operator or function used in
WHERE is properly marked as strict.

			regards, tom lane