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Re: bug in join?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Laurette Cisneros <laurette(at)nextbus(dot)com>
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: bug in join?
Date: 2002-01-03 00:02:51
Message-ID: 8128.1010016171@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Okay, I've been able to reproduce the problem here.  Looks like the
eqjoinsel math is not wrong, exactly, but small roundoff errors are
causing the logic to do unreasonable things.  I think
get_att_numdistinct needs to round its result to an integer, and
probably there needs to be some clamping of computed probabilities to
the 0..1 range (otherfreq1 is coming out about -4.4703483581542969e-08
in this example, which should be clamped to 0).

Will have a fix late tonight or tomorrow.

Thanks for the example case!

			regards, tom lane

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