| From: | "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru> |
|---|---|
| To: | Aleksander Alekseev <aleksander(at)timescale(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Hannu Krosing <hannuk(at)google(dot)com>, Peter Eisentraut <peter(at)eisentraut(dot)org> |
| Subject: | Re: What is a typical precision of gettimeofday()? |
| Date: | 2024-07-03 10:38:14 |
| Message-ID: | F9F051F4-FED4-4391-AF2A-40663A7D85A0@yandex-team.ru |
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| Lists: | pgsql-hackers |
> On 3 Jul 2024, at 13:48, Aleksander Alekseev <aleksander(at)timescale(dot)com> wrote:
>
> Hi,
>
>> That’s a very interesting result, from the UUID POV!
>> If time is almost always advancing, using time readings instead of a counter is very reasonable: we have interprocess monotonicity almost for free.
>> Though time is advancing in a very small steps… RFC assumes that we use microseconds, I’m not sure it’s ok to use 10 more bits for nanoseconds…
>
> A counter is mandatory since someone can for instance change the
> system's time while the process is generating UUIDs. You can't
> generally assume that local time of the system is monotonic.
AFAIR according to RFC when time jumps backwards, we just use time microseconds as a counter. Until time starts to advance again.
Best regards, Andrey Borodin.
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