| From: | "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru> |
|---|---|
| To: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Cc: | Sergey Prokhorenko <sergeyprokhorenko(at)yahoo(dot)com(dot)au>, Jelte Fennema-Nio <postgres(at)jeltef(dot)nl>, Michael Paquier <michael(at)paquier(dot)xyz>, Aleksander Alekseev <aleksander(at)timescale(dot)com>, pgsql-hackers mailing list <pgsql-hackers(at)postgresql(dot)org>, Peter Eisentraut <peter(at)eisentraut(dot)org>, Przemysław Sztoch <przemyslaw(at)sztoch(dot)pl>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Mat Arye <mat(at)timescaledb(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Nikolay Samokhvalov <samokhvalov(at)gmail(dot)com>, Junwang Zhao <zhjwpku(at)gmail(dot)com>, Stepan Neretin <sncfmgg(at)gmail(dot)com> |
| Subject: | Re: UUID v7 |
| Date: | 2024-11-06 18:14:29 |
| Message-ID: | 5819C3A4-C438-4F61-B7F6-0CB37FAE434F@yandex-team.ru |
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| Lists: | pgsql-hackers |
> On 5 Nov 2024, at 23:56, Andrey M. Borodin <x4mmm(at)yandex-team(dot)ru> wrote:
>
> <v30-0001-Implement-UUID-v7.patch>
Some more thoughts on this patch version:
0. Comment mentioning nanoseconds, while we do not need to carry anything
/* Convert TimestampTz back and carry nanoseconds. */
1. There's unnecessary &3 in
uuid->data[7] = uuid->data[7] | ((uuid->data[8] >> 6) & 3);
2. Currently we store 0..999 microseconds in 10 bits, so values 1000..1023 are unused. We could use them for overflow. That would slightly increase non-overflowing capacity when generating more than million UUIDs per second on one backend. However, given current performance of our CSPRNG I do not think this feature worth code complexity.
Best regards, Andrey Borodin.
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