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pgsql: Tweak joinlist creation to avoid generating useless one-element

From: tgl(at)postgresql(dot)org (Tom Lane)
To: pgsql-committers(at)postgresql(dot)org
Subject: pgsql: Tweak joinlist creation to avoid generating useless one-element
Date: 2007-01-08 16:47:30
Message-ID: 20070108164730.475449FB1BF@postgresql.org (view raw or flat)
Thread:
Lists: pgsql-committers
Log Message:
-----------
Tweak joinlist creation to avoid generating useless one-element subproblems
when collapsing of JOIN trees is stopped by join_collapse_limit.  For instance
a list of 11 LEFT JOINs with limit 8 now produces something like
	((1 2 3 4 5 6 7 8) 9 10 11 12)
instead of
	(((1 2 3 4 5 6 7 8) (9)) 10 11 12)
The latter structure is really only required for a FULL JOIN.
Noted while studying an example from Shane Ambler.

Modified Files:
--------------
    pgsql/src/backend/optimizer/plan:
        initsplan.c (r1.126 -> r1.127)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/initsplan.c.diff?r1=1.126&r2=1.127)

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Subject: pgsql: Tweak joinlist creation to avoid generating useless one-element
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Subject: pgsql: Remove cost_hashjoin's very ancient hack to discourage (once,

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