| From: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
|---|---|
| To: | "Jonathan S(dot) Katz" <jkatz(at)postgresql(dot)org> |
| Cc: | Zhihong Yu <zyu(at)yugabyte(dot)com>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: unnesting multirange data types |
| Date: | 2021-06-13 15:49:07 |
| Message-ID: | 20210613154907.GZ16435@telsasoft.com |
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| Lists: | pgsql-hackers |
On Sun, Jun 13, 2021 at 11:25:05AM -0400, Jonathan S. Katz wrote:
> On 6/13/21 10:57 AM, Zhihong Yu wrote:
> > +/* Turn multirange into a set of ranges */
> >
> > set of ranges: sequence of ranges
>
> I believe "set of ranges" is accurate here, as the comparable return is
> a "SETOF rangetype". Sequences are objects unto themselves.
>
I believe the point was that (in mathematics) a "set" is unordered, and a
sequence is ordered. Also, a "setof" tuples in postgres can contain
duplicates.
The docs say "The ranges are read out in storage order (ascending).", so I
think this is just a confusion between what "set" means in math vs in postgres.
In postgres, "sequence" usually refers to the object that generarates a
sequence:
| CREATE SEQUENCE creates a new sequence number generator.
--
Justin
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