Re: Infinities in type numeric

On 6/12/20 7:00 PM, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Thu, Jun 11, 2020 at 9:16 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> We had a discussion recently about how it'd be a good idea to support
>>> infinity values in type numeric [1].
>
>> FWIW, I don't particularly like the idea. Back when I was an
>> application developer, I remember having to insert special cases into
>> any code that dealt with double precision to deal with +/-Inf and NaN.
>> I was happy that I didn't need them for numeric, too. So this change
>> would have made me sad.
>
> Well, you're already stuck with special-casing numeric NaN, so I'm
> not sure that Inf makes your life noticeably worse on that score.
>
> This does tie into something I have a question about in the patch's
> comments though. As the patch stands, numeric(numeric, integer)
> (that is, the typmod-enforcement function) just lets infinities
> through regardless of the typmod, on the grounds that it is/was also
> letting NaNs through regardless of typmod. But you could certainly
> make the argument that Inf should only be allowed in an unconstrained
> numeric column, because by definition it overflows any finite precision
> restriction. If we did that, you'd never see Inf in a
> standard-conforming column, since SQL doesn't allow unconstrained
> numeric columns IIRC.

It does. The precision and scale are both optional.

If the precision is missing, it's implementation defined; if the scale
is missing, it's 0.
--
Vik Fearing