Re: numeric stddev_pop and var_pop are wrong

From: Neil Conway <neilc(at)samurai(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-bugs(at)postgreSQL(dot)org, student23 <student23(at)o2(dot)pl>
Subject: Re: numeric stddev_pop and var_pop are wrong
Date: 2007-07-10 06:10:55
Message-ID: 1184047855.8180.17.camel@goldbach
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On Mon, 2007-09-07 at 10:39 -0400, Tom Lane wrote:
> When applied to "numeric" input, stddev_pop produces the same result as
> stddev_samp, and var_pop produces the same result as var_samp. This
> is because whoever wrote numeric_stddev_internal() forgot that the
> divisor is different for the sample case. This mistake is in fact
> visible in the regression test outputs for the function, so those
> outputs weren't checked very carefully :-(

My fault, I'm afraid -- how embarrassing! I certainly tested the
function for numeric inputs while developing it. I can only guess that I
wrote it and tested it, then refactored and broke it, and blindly copied
the resulting regression outputs => expected...



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