Re: [RFC] ASOF Join
| От | Isaac Morland |
|---|---|
| Тема | Re: [RFC] ASOF Join |
| Дата | |
| Msg-id | CAMsGm5c05UDYys2avxtRU-btnMoA=f42ajwmKWg-V8KaYGdJ_g@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [RFC] ASOF Join (Chapman Flack <chap@anastigmatix.net>) |
| Ответы |
Re: [RFC] ASOF Join
|
| Список | pgsql-hackers |
On Tue, 23 Nov 2021 at 09:44, Chapman Flack <chap@anastigmatix.net> wrote:
On 11/23/21 02:29, Ilya Anfimov wrote:
> (*We
> strangely don't have an absolute value operator on interval, but
> I think you've got the point*).
Although tangential to the topic, that might be because a PG interval
is a triple of independently-signed months/days/seconds components.
An interval like '1 month -31 days +12:00:00' is positive or negative
depending on the absolute date you apply it to, so what its absolute
value should be isn't clear in isolation.
Umm, it's definitely negative:
odyssey=> select '1 month -31 days +12:00:00'::interval < '0 months'::interval;
?column?
----------
t
(1 row)
?column?
----------
t
(1 row)
It's just that due to the complexities of our calendar/time systems, adding it to a timestamp can move the timestamp in either direction:
odyssey=> select '2021-02-01'::timestamp + '1 month -31 days +12:00:00'::interval;
?column?
---------------------
2021-01-29 12:00:00
(1 row)
odyssey=> select '2021-03-01'::timestamp + '1 month -31 days +12:00:00'::interval;
?column?
---------------------
2021-03-01 12:00:00
(1 row)
?column?
---------------------
2021-01-29 12:00:00
(1 row)
odyssey=> select '2021-03-01'::timestamp + '1 month -31 days +12:00:00'::interval;
?column?
---------------------
2021-03-01 12:00:00
(1 row)
I'm working on a patch to add abs(interval) so I noticed this. There are lots of oddities, including lots of intervals which compare equal to 0 but which can change a timestamp when added to it, but as presently designed, this particular interval compares as negative.
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