Обсуждение: INT4RANGE Upper bound always includes a higher number

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Page: https://www.postgresql.org/docs/16/rangetypes.html
Description:

Hi,
First I just wanted to say, the documentation is overall excellent, it has
been such a pleasure learning postgres.
In the RANGE types where it says the square bracket indicates upper bound
inclusive ],
But the issue with this is when I do upper bound inclusive it always goes
one number above. 
This is contrary to your documentation says and it is also counter
intuitive.
According to your example (copied from your docs):

-- includes 3, does not include 7, and does include all points in between
SELECT '[3,7)'::int4range;

But this is not true, it shows 3 and 7

And if i do:
SELECT '(3,7]'::INT4RANGE;
It shows:

 [4,8)
(1 row)

Please can someone explain ?

Thank you

PG Doc comments form <noreply@postgresql.org> writes:
> According to your example (copied from your docs):

> -- includes 3, does not include 7, and does include all points in between
> SELECT '[3,7)'::int4range;

> But this is not true, it shows 3 and 7

What's not true about it?

postgres=# SELECT 3 <@ '[3,7)'::int4range;
 ?column? 
----------
 t
(1 row)

postgres=# SELECT 6 <@ '[3,7)'::int4range;
 ?column? 
----------
 t
(1 row)

postgres=# SELECT 7 <@ '[3,7)'::int4range;
 ?column? 
----------
 f
(1 row)

7 is not a member of that range, only an endpoint.

> And if i do:
> SELECT '(3,7]'::INT4RANGE;
> It shows:

>  [4,8)
> (1 row)

This is a consequence of canonicalization.  There are four different
ways to write the same integer range:

    [3,6]
    [3,7)
    (2,6]
    (2,7)

All of these include 3,4,5,6 and no other integer.

INT4RANGE has a canonicalize function that converts ranges into the
"[m,n)" form so that ranges that are functionally identical look
identical.  If you don't like that, you can make a user-defined
range type with a different canonicalize function, or none at all.
See

https://www.postgresql.org/docs/current/rangetypes.html#RANGETYPES-DISCRETE

            regards, tom lane