Re: pgsql: Fix NUMERIC modulus to properly truncate

Christopher Kings-Lynne <chriskl@familyhealth.com.au> writes:
>> No, I don't think so.  It doesn't seem to be something that enough
>> people use to risk the change in behavior --- it might break something
>> that was working.  But, if folks want it backported we can do it.  It is
>> only a change to properly do modulus for numeric.

> Well, from my point of view it's an absolute mathematical error - i'd
> backport it.  I can't see anyone relying on it :)

Doesn't this patch break the basic theorem that

    a = trunc(a / b) * b + (a mod b)

?  If division rounds and mod doesn't, you've got pretty serious issues.

            regards, tom lane