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Re: Merge join bug?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Bugs for PostgreSQL <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: Merge join bug?
Date: 2006-03-17 19:39:17
Message-ID: 9479.1142624357@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> Someone has reported to me that VACUUM ANALYZE is causing different
> results for the same query.  They believe it is caused by merge join.

Fixed; bug was introduced here:

2005-05-13 17:20  tgl

	* src/: backend/executor/nodeMergejoin.c,
	include/executor/execdebug.h, include/executor/execdefs.h,
	include/nodes/execnodes.h: Revise nodeMergejoin in light of example
	provided by Guillaume Smet.  When one side of the join has a NULL,
	we don't want to uselessly try to match it against every remaining
	tuple of the other side.  While at it, rewrite the comparison
	machinery to avoid multiple evaluations of the left and right input
	expressions and to use a btree comparator where available, instead
	of double operator calls.  Also revise the state machine to
	eliminate redundant comparisons and hopefully make it more readable
	too.

			regards, tom lane

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