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Date: Fri, 5 Jun 2009 08:01:51 -0700 (PDT)
From: chester c young <chestercyoung@yahoo.com>
Subject: do unneeded outer joins cost?
To: sql pgsql <pgsql-sql@postgresql.org>
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for example:

select    t1.*
from      t1
left join t2 on( <expensive condition> );

since t2 is not used in the result nor is it used in determining the result, is the <expensive condition> to left join t2 used?

(the question goes as to how much generated sql needs to be cleaned to be efficient)