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
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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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