Обсуждение: Why does the range type's upper function behave inconsistently?

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Hello,

On 05/07/2015 19:13, Dane Foster wrote:
> I don't understand the inconsistent behavior of the range types'
> upper function in regard to inclusive ranges.
>
> For example(s): 1. SELECT upper(int4range(1, 4, '[]')) = 4; --
> FALSE 2. SELECT upper(int8range(1, 4, '[]')) = 4; -- FALSE 3.
> SELECT upper(numrange(1, 4, '[]')) = 4; -- TRUE 4. SELECT
> upper(tstzrange('2015-07-01: 00:00:00', now(), '[]')) = now(); --
> TRUE 5. SELECT upper(daterange('2015-01-01', current_date, '[]'))
> = current_date; -- FALSE
>
> #1 & #2 are FALSE because upper returns 5 instead of 4; and #5 is
> FALSE because upper returns: current_date + interval '1 day'. I
> don't understand the logic behind why it would return the inclusive
> upper bound value for some ranges and not others. If anyone can
> shed some light on this behavior it would be greatly appreciated.
>
> One of things I originally tried to use upper for was CHECK
> constraints. That was until I wrote some unit tests and realized
> that upper doesn't consistently work the way I expected. Of course
> my assumptions are probably wrong so that's why I'm asking for
> clarification.
>

Because for discrete range types, the canonical form is used, which is
[). Check
http://www.postgresql.org/docs/current/static/rangetypes.html and the
discrete range types paragraph.

Regards.

> Regards,
>
> Dane


- --
Julien Rouhaud
http://dalibo.com - http://dalibo.org
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Dane Foster <studdugie@gmail.com> writes:
> I don't understand the inconsistent behavior of the range types' upper
> function in regard to inclusive ranges.

The behavior is different for discrete vs. continuous ranges.  For
example,

regression=# select int4range(1, 4, '[]');
 int4range
-----------
 [1,5)
(1 row)

regression=# select numrange(1, 4, '[]');
 numrange
----------
 [1,4]
(1 row)

In the discrete case we normalize the bounds to '[)' style so that ranges
that contain the same sets of values will compare as equal even when they
were written differently.  But there's no practical way to do that for
continuous types.  See
http://www.postgresql.org/docs/9.4/static/rangetypes.html#RANGETYPES-DISCRETE

            regards, tom lane

On 07/05/2015 10:13 AM, Dane Foster wrote:
> I don't understand the inconsistent behavior of the range types' upper
> function in regard to inclusive ranges.
>
> For example(s):
> 1. SELECT upper(int4range(1, 4, '[]')) = 4; -- FALSE
> 2. SELECT upper(int8range(1, 4, '[]')) = 4; -- FALSE
> 3. SELECT upper(numrange(1, 4, '[]')) = 4; -- TRUE
> 4. SELECT upper(tstzrange('2015-07-01: 00:00:00', now(), '[]')) = now();
> -- TRUE
> 5. SELECT upper(daterange('2015-01-01', current_date, '[]')) =
> current_date; -- FALSE

To follow up on Julien Rouhaud post, if you do:

production=# select daterange('2015-01-01', current_date, '[]');
         daterange
-------------------------
  [2015-01-01,2015-07-06)
(1 row)

see that the '[]] has been changed to '[)' with tomorrows date as the
upper bound.

>
> #1 & #2 are FALSE because upper returns 5 instead of 4; and #5 is FALSE
> because upper returns: current_date + interval '1 day'. I don't
> understand the logic behind why it would return the inclusive upper
> bound value for some ranges and not others. If anyone can shed some
> light on this behavior it would be greatly appreciated.
>
> One of things I originally tried to use upper for was CHECK constraints.
> That was until I wrote some unit tests and realized that upper doesn't
> consistently work the way I expected. Of course my assumptions are
> probably wrong so that's why I'm asking for clarification.
>
> Regards,
>
> Dane


--
Adrian Klaver
adrian.klaver@aklaver.com