Re: Interval aggregate regression failure (expected seems

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Michael Paesold <mpaesold(at)gmx(dot)at>
Cc: Michael Glaesemann <grzm(at)myrealbox(dot)com>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: Interval aggregate regression failure (expected seems
Date: 2005-11-08 22:48:16
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Michael Paesold <mpaesold(at)gmx(dot)at> writes:
> Would you mind reporting this to RedHat Bugzilla? I believe a bug report
> from you would have more weight then mine, because you actually
> understand what's going on here. :-)

Actually, given the thought that this may be an artifact of keeping an
intermediate value in a wider-than-normal register rather than genuinely
rearranging the computation, I'm not certain it is a compiler bug.
We'd have to study it a lot more closely before filing it as one, anyway.

If you accept the idea that the pentium4 answer is the right one,
then what we really need to do is focus on a better rounding rule than
"strict truncation". I was toying with the notion of adding the
equivalent of half a microsecond to the fractional-day value before
truncating it to integer. But I'm not certain that that wouldn't have
some bad effects in other cases.

regards, tom lane

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