Re: NaNs in numeric_power (was Re: Postgres 11 release notes)

On 15 May 2018 at 22:55, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> David Rowley <david.rowley@2ndquadrant.com> writes:
>> On 16 May 2018 at 02:01, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> I'm not particularly fussed about getting credit for that.  However,
>>> looking again at how that patch series turned out --- ie, that
>>> we ensured POSIX behavior for NaNs only in HEAD --- I wonder
>>> whether we shouldn't do what was mentioned in the commit log for
>>> 6bdf1303, and teach numeric_pow() about these same special cases.
>>> It seems like it would be more consistent to change both functions
>>> for v11, rather than letting that other shoe drop in some future
>>> major release.
>
>> I'm inclined to agree. It's hard to imagine these two functions
>> behaving differently in regards to NaN input is useful to anyone.
>
> Here's a proposed patch for that.
>

In the case 1 ^ NaN = 1, what should the result scale be?

For other inputs, the result scale is at least as large as the scale
of the first input, so I would suggest that the same ought to be the
case here.

Otherwise, this looks fine, and I agree that it makes thinks neater /
more consistent.

Regards,
Dean