From: | Nathan Boley <npboley(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Scott Bailey <artacus(at)comcast(dot)net>, hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Range types |
Date: | 2009-12-14 18:00:08 |
Message-ID: | 6fa3b6e20912141000l26ec0bfakb23bb3dffb8b1cbb@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
>> Because intervals (mathematical not SQL) can be open or closed at each
>> end point we need to know what the next an previous value would be at
>> the specified granularity. And while you can do some operations without
>> knowing this, there are many you can't. For instance you could not tell
>> whether two [] or () ranges were adjacent, or be able to coalesce an
>> array of ranges.
>
> This statement seems to me to demonstrate that you don't actually
> understand the concept of open and closed ranges. It has nothing
> whatsoever to do with assuming that the data type is discrete;
> these concepts are perfectly well defined for the reals, for example.
> What it is about is whether the inclusion conditions are "< bound"
> or "<= bound".
IMHO the first question is whether, for integers, [1,2] UNION [3,5]
should be equal to [1,5]. In math this is certainly true, and defining
'next' seems like a reasonable way to establish this in postgres.
The next question is whether, for floats, [1,3-FLT_EPSILON] UNION
[3,5] should be [1,5].
And the next question is whether, for numeric(6,2), [1,2.99] UNION
[3,5] should be [1,5].
FWIW, I would answer yes, no, yes to those three questions.
-Nathan
From | Date | Subject | |
---|---|---|---|
Next Message | Jeff Davis | 2009-12-14 18:02:38 | Re: Range types |
Previous Message | Robert Haas | 2009-12-14 17:42:58 | Re: new CommitFest states |