From: Tom Lane <tgl@sss.pgh.pa.us>
To: themyth.cs@gmail.com
cc: pgsql-docs@lists.postgresql.org
Subject: Re: INT4RANGE Upper bound always includes a higher number
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Comments: In-reply-to PG Doc comments form <noreply@postgresql.org>
	message dated "Tue, 03 Oct 2023 19:00:49 -0000"
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Date: Tue, 03 Oct 2023 16:57:32 -0400
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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