Date: Thu, 2 Nov 2023 10:14:58 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>, jani.rahkola@iki.fi,
	pgsql-docs@lists.postgresql.org
Subject: Re: Documentation of return values of range functions lower and upper
Message-ID: <ZUOu4maaCXivToUE@momjian.us>
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On Thu, Nov  2, 2023 at 08:56:13AM +0100, Laurenz Albe wrote:
> On Wed, 2023-11-01 at 18:03 -0400, Bruce Momjian wrote:
> > On Wed, Nov  1, 2023 at 09:40:43PM +0100, Laurenz Albe wrote:
> > > > 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?".
> > 
> > I had to go with "Is the multirange's lower bound unbounded?" because
> > the surrounding items use that sentence structure.  Patch attached.
> 
> Better, though "Is the range's upper bound unbounded?" makes me cringe.

Oh, yeah, totally cringe, me too.  :-)

> It is not the bound that is bounded or not, but the range.
> 
> How about "Is the range unbounded at the upper end?" or "Does the range
> have no upper bound?"

I used your "end" idea to modify the patch, attached.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.

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diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index c76ec52c55..c2f266ea24 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -19905,7 +19905,7 @@ SELECT NULLIF(value, '(none)') ...
        </para>
        <para>
         Extracts the lower bound of the range (<literal>NULL</literal> if the
-        range is empty or the lower bound is infinite).
+        range is empty or unbounded).
        </para>
        <para>
         <literal>lower(numrange(1.1,2.2))</literal>
@@ -19923,7 +19923,7 @@ SELECT NULLIF(value, '(none)') ...
        </para>
        <para>
         Extracts the upper bound of the range (<literal>NULL</literal> if the
-        range is empty or the upper bound is infinite).
+        range is empty or unbounded).
        </para>
        <para>
         <literal>upper(numrange(1.1,2.2))</literal>
@@ -19991,7 +19991,8 @@ SELECT NULLIF(value, '(none)') ...
         <returnvalue>boolean</returnvalue>
        </para>
        <para>
-        Is the range's lower bound infinite?
+        Is the range's lower end unbounded?  A +/-Infinity lower
+        bound returns false.
        </para>
        <para>
         <literal>lower_inf('(,)'::daterange)</literal>
@@ -20008,7 +20009,8 @@ SELECT NULLIF(value, '(none)') ...
         <returnvalue>boolean</returnvalue>
        </para>
        <para>
-        Is the range's upper bound infinite?
+        Is the range's upper end unbounded?  A +/-Infinity upper
+        bound returns false.
        </para>
        <para>
         <literal>upper_inf('(,)'::daterange)</literal>
@@ -20063,7 +20065,7 @@ SELECT NULLIF(value, '(none)') ...
        </para>
        <para>
         Extracts the lower bound of the multirange (<literal>NULL</literal> if the
-        multirange is empty or the lower bound is infinite).
+        multirange is empty or unbounded).
        </para>
        <para>
         <literal>lower('{[1.1,2.2)}'::nummultirange)</literal>
@@ -20081,7 +20083,7 @@ SELECT NULLIF(value, '(none)') ...
        </para>
        <para>
         Extracts the upper bound of the multirange (<literal>NULL</literal> if the
-        multirange is empty or the upper bound is infinite).
+        multirange is empty or unbounded).
        </para>
        <para>
         <literal>upper('{[1.1,2.2)}'::nummultirange)</literal>
@@ -20149,7 +20151,8 @@ SELECT NULLIF(value, '(none)') ...
         <returnvalue>boolean</returnvalue>
        </para>
        <para>
-        Is the multirange's lower bound infinite?
+        Is the multirange's lower end unbounded?  A +/-Infinity lower
+        bound returns false.
        </para>
        <para>
         <literal>lower_inf('{(,)}'::datemultirange)</literal>
@@ -20166,7 +20169,8 @@ SELECT NULLIF(value, '(none)') ...
         <returnvalue>boolean</returnvalue>
        </para>
        <para>
-        Is the multirange's upper bound infinite?
+        Is the multirange's upper end unbounded?  A +/-Infinity upper
+        bound returns false.
        </para>
        <para>
         <literal>upper_inf('{(,)}'::datemultirange)</literal>

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