Re: Improve examples for range operators

On Wed, Feb 20, 2019 at 12:27:26PM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/11/functions-range.html
> Description:
>
> Hi.
>
> It would be nice if next examples:
>
> << strictly left of int8range(1,10) << int8range(100,110) t
> >> strictly right of int8range(50,60) >> int8range(20,30) t
> &< does not extend to the right of int8range(1,20) &< int8range(18,20)
> t
> &> does not extend to the left of int8range(7,20) &> int8range(5,10) t
>
> are extended by:
> **not** strictly left of, **not** strictly right of, **extends** to the
> right of, **extends** to the left of
>
> Because without manual experiments I can not imagine the ranges that cause
> 'false' result for the examples above.

Well, they are not technically negatives of each other. << means the
first is all left of the second, while &< means that it doesn't go to
the right of the second, e.g.,

SELECT int8range(1,10) &< int8range(100,110);
?column?
----------
t

SELECT int8range(1,105) &< int8range(100,110);
?column?
----------
t

SELECT int8range(1,200) &< int8range(100,110);
?column?
----------
f

Notice it changed from true to false and none of these was strictly to
the right.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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