On Wed, 2023-11-01 at 16:28 -0400, Bruce Momjian wrote: > On Wed, Nov 18, 2020 at 05:28:44PM +0100, Laurenz Albe wrote: > > On Wed, 2020-11-18 at 22:49 +0900, Fujii Masao wrote: > > > On 2020/11/12 17:14, Laurenz Albe wrote: > > > > On Wed, 2020-11-11 at 18:19 +0100, Laurenz Albe wrote: > > > > > > Table 9.54 in page > > > > > > https://www.postgresql.org/docs/current/functions-range.html states > > > > > > that the > > > > > > functions lower and upper return NULL if the requested bound is > > > > > > infinite. If > > > > > > the element type of the range contains the special values infinity > > > > > > and > > > > > > -infinity, this is not correct, as those values are returned if > > > > > > explicitly > > > > > > used as either bound. > > > > > +1 > > > > > Perhaps it would be better to say > > > > > NULL if the range is empty or has no lower/upper bound > > > > > > I agree this description looks a bit confusing. But according to the > > > section > > > "Infinite (Unbounded) Ranges" (*1), we already call "lower/upper bound > > > omitted" just infinite. So I don't think the current description is > > > incorrect. > > > > > > (*1) > > > https://www.postgresql.org/docs/devel/rangetypes.html#RANGETYPES-INFINITE > > > > That is correct, but I'd argue that it would be better to clarify the > > paragraph too, > > in particular: > > > > The functions lower_inf and upper_inf test for infinite lower and upper > > bounds of a range, respectively. > > > > should better read > > > > The functions lower_inf and upper_inf test for omitted lower and upper > > bounds of a range, respectively. > > > > The rest of the paragraph is pretty unambiguous. > > > > > > Independent of this, I think that my patch for "upper" and "lower" would > > make the > > documentation clearer. > > Yes, I agree this documentation needs help. > > For upper/lower(), it is clear that the documentation is better saying > "unspecified" rather than infinite. The fact that upper/lower_inf() > returns false for +/-Infinity is quite odd, but should at least be > documented. > > Patch attached. It is odd that +Infinity (vs. Infinity) wasn't > supported for datetime input until PG 16, but I think we have to say > +/-infinity vs (blank)/-Infinity. > > Patch attached.
I am unhappy with "unspecified". A NULL value as upper or lower bound has a very specific meaning, namely that the range is unbounded in that direction. This is a bit confusing, since NULL is typically used for unknown or undefined values. I think it would be better to say "returns NULL if the range is empty or unbounded" and "is the range unbounded on the upper end?". Yours, Laurenz Albe
