Re: UUID v7

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От Aleksander Alekseev
Тема Re: UUID v7
Дата
Msg-id CAJ7c6TPh5wbPDEoDa2-9w5N=eEsK4tqA4dGidnays6e=8T20Qg@mail.gmail.com
обсуждение исходный текст
Ответ на Re: UUID v7  (Andrey Borodin <x4mmm@yandex-team.ru>)
Ответы Re: UUID v7  (Sergey Prokhorenko <sergeyprokhorenko@yahoo.com.au>)
Список pgsql-hackers
Hi Andrey,

> > Timestamp and TimestampTz are absolutely the same thing.
> My question is not about Postgres data types. I'm asking about examples in the standard.
>
> There's an example 017F22E2-79B0-7CC3-98C4-DC0C0C07398F. It is expected to be generated on "Tuesday, February 22,
20222:22:22.00 PM GMT-05:00".
 
> It's exaplained to be 164555774200000ns after 1582-10-15 00:00:00 UTC.
>
> But 164555774200000ns after 1582-10-15 00:00:00 UTC  was  2022-02-22 19:22:22 UTC. And that was 2022-02-23 00:22:22
inUTC-05.
 

Not 100% sure which text you are referring to exactly, but I'm
guessing it's section B.2 of [1]

"""
This example UUIDv7 test vector utilizes a well-known 32 bit Unix
epoch with additional millisecond precision to fill the first 48 bits
[...]
The timestamp is Tuesday, February 22, 2022 2:22:22.00 PM GMT-05:00
represented as 0x17F22E279B0 or 1645557742000
"""

If this is the case, I think the example is indeed wrong:

```
=# select extract(epoch from 'Tuesday, February 22, 2022 2:22:22.00 PM
GMT-05:00' :: timestamptz)*1000;
       ?column?
----------------------
 1645521742000.000000
(1 row)
```

And the difference between the value in the text and the actual value
is 10 hours as you pointed out.

Also you named the date 1582-10-15 00:00:00 UTC. Maybe you actually
meant 1970-01-01 00:00:00 UTC?

[1]: https://www.ietf.org/archive/id/draft-peabody-dispatch-new-uuid-format-04.html

-- 
Best regards,
Aleksander Alekseev



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