On Wed, Jun 17, 2020 at 6:33 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Alexander Korotkov <a.korot...@postgrespro.ru> writes: > > On Thu, Jun 11, 2020 at 10:00 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > >> I don't think this is very relevant. The SQL standard has not got the > >> concepts of Inf or NaN either (see 4.4.2 Characteristics of numbers), > >> therefore their definition is only envisioning that a string > representing > >> a normal finite number should be castable to DOUBLE PRECISION. Thus, > >> both of the relevant standards think that "numbers" are just finite > >> numbers. > > > Yes, I see. No standard insists we should support NaN. However, > > standard claims .double() should behave the same as CAST to double. > > So, I think if CAST supports NaN, but .double() doesn't, it's still a > > violation. > > No, I think you are completely misunderstanding the standard. They > are saying that strings that look like legal numbers according to SQL > should be castable into numbers. But NaN and Inf are not legal > numbers according to SQL, so there is nothing in that text that > justifies accepting "NaN". Nor does the JSON standard provide any > support for that position. So I think it is fine to leave NaN/Inf > out of the world of what you can write in jsonpath. >
rfc and sql json forbid Nan and Inf ( Technical Report is freely available, https://standards.iso.org/ittf/PubliclyAvailableStandards/c067367_ISO_IEC_TR_19075-6_2017.zip ) Page 10 JSON terminology. “A sequence comprising an integer part, optionally followed by a fractional part and/or an exponent part (non-numeric values, such as infinity and NaN are not permitted)” > > I'd be more willing to let the code do this if it didn't require such > a horrid, dangerous kluge to do so. But it does, and I don't see any > easy way around that, so I think we should just take out the kluge. > And do so sooner not later, before some misguided user starts to > depend on it. > The problem is that we tried to find a trade-off between standard and postgres implementation, for example, in postgres CAST allows NaN and Inf, and SQL Standard requires .double should works as CAST. SELECT 'nan'::real, 'inf'::real; float4 | float4 --------+---------- NaN | Infinity (1 row) > > regards, tom lane > > > -- Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
