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  1. Fix constant when extracting timestamp from UUIDv7.

  1. Fix for typo in UUIDv7 timestamp extraction

    Erik Nordström <erik@tigerdata.com> — 2025-08-13T08:05:04Z

    Hi,

I think I found a small typo in the function that extracts a timestamp from
a UUIDv7 (uuid_extract_timestamp). Unless I am mistaken, the constant
US_PER_MS should be used instead of NS_PER_US when converting milliseconds
to microseconds. Fortunately, these constants are the same so the
calculation is still correct.

Anyway, attaching a patch to fix this typo.

On a related note, I am wondering why this function doesn't extract and use
the sub-millisecond information in the rand_a bits? These bits are added
when generating the UUID, but they don't seem to be extracted. Hopefully
somebody could shed some light on this and whether it would be a worthwhile
addition.

Thank you,

- Erik

  2. Re: Fix for typo in UUIDv7 timestamp extraction

    x4mmm@yandex-team.ru — 2025-08-13T09:52:04Z

    Hi Erik!

> On 13 Aug 2025, at 11:05, Erik Nordström <erik@tigerdata.com> wrote:
> 
> I think I found a small typo in the function that extracts a timestamp from a UUIDv7 (uuid_extract_timestamp). Unless I am mistaken, the constant US_PER_MS should be used instead of NS_PER_US when converting milliseconds to microseconds. Fortunately, these constants are the same so the calculation is still correct.

Wow, that's a very good level of proofreading! Yes, you are correct, it's must be US_PER_MS.

> 
> Anyway, attaching a patch to fix this typo. 

LGTM.


> 
> On a related note, I am wondering why this function doesn't extract and use the sub-millisecond information in the rand_a bits? These bits are added when generating the UUID, but they don't seem to be extracted. Hopefully somebody could shed some light on this and whether it would be a worthwhile addition.

UUID might be formed by any external system, rand_a bits are not guaranteed to be non-random. Well, in some sense, reading time is reading random number, but anyway, we don't know for sure how those bits are used. And even in Postgres usage of sub-millisecond fractions depends on OS.

I think we can have a function in an extensions, that does pretend that UUID was generated by known algorithm. Or even SQL function to extract microseconds.

Thanks!


Best regards, Andrey Borodin.

  3. Re: Fix for typo in UUIDv7 timestamp extraction

    Erik Nordström <erik@tigerdata.com> — 2025-08-13T12:53:43Z

    On Wed, Aug 13, 2025 at 11:52 AM Andrey Borodin <x4mmm@yandex-team.ru>
wrote:

> Hi Erik!
>
> > On 13 Aug 2025, at 11:05, Erik Nordström <erik@tigerdata.com> wrote:
> >
> > I think I found a small typo in the function that extracts a timestamp
> from a UUIDv7 (uuid_extract_timestamp). Unless I am mistaken, the constant
> US_PER_MS should be used instead of NS_PER_US when converting milliseconds
> to microseconds. Fortunately, these constants are the same so the
> calculation is still correct.
>
> Wow, that's a very good level of proofreading! Yes, you are correct, it's
> must be US_PER_MS.
>
> >
> > Anyway, attaching a patch to fix this typo.
>
> LGTM.
>

Ok, maybe a committer would like to commit this change immediately?

>
>
> >
> > On a related note, I am wondering why this function doesn't extract and
> use the sub-millisecond information in the rand_a bits? These bits are
> added when generating the UUID, but they don't seem to be extracted.
> Hopefully somebody could shed some light on this and whether it would be a
> worthwhile addition.
>
> UUID might be formed by any external system, rand_a bits are not
> guaranteed to be non-random. Well, in some sense, reading time is reading
> random number, but anyway, we don't know for sure how those bits are used.
> And even in Postgres usage of sub-millisecond fractions depends on OS.
>
> I think we can have a function in an extensions, that does pretend that
> UUID was generated by known algorithm. Or even SQL function to extract
> microseconds.
>
>
That's what I suspected. Thanks for clarifying.

Best,

Erik

  4. Re: Fix for typo in UUIDv7 timestamp extraction

    Masahiko Sawada <sawada.mshk@gmail.com> — 2025-08-15T18:44:53Z

    On Thu, Aug 14, 2025 at 5:10 AM Erik Nordström <erik@tigerdata.com> wrote:
>
>
>
> On Wed, Aug 13, 2025 at 11:52 AM Andrey Borodin <x4mmm@yandex-team.ru> wrote:
>>
>> Hi Erik!
>>
>> > On 13 Aug 2025, at 11:05, Erik Nordström <erik@tigerdata.com> wrote:
>> >
>> > I think I found a small typo in the function that extracts a timestamp from a UUIDv7 (uuid_extract_timestamp). Unless I am mistaken, the constant US_PER_MS should be used instead of NS_PER_US when converting milliseconds to microseconds. Fortunately, these constants are the same so the calculation is still correct.
>>
>> Wow, that's a very good level of proofreading! Yes, you are correct, it's must be US_PER_MS.
>>
>> >
>> > Anyway, attaching a patch to fix this typo.
>>
>> LGTM.
>
>
> Ok, maybe a committer would like to commit this change immediately?

Thank you for the report! I'll push the patch to master and v18 shortly.

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com

  5. Re: Fix for typo in UUIDv7 timestamp extraction

    Masahiko Sawada <sawada.mshk@gmail.com> — 2025-08-15T19:01:14Z

    On Fri, Aug 15, 2025 at 11:44 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Thu, Aug 14, 2025 at 5:10 AM Erik Nordström <erik@tigerdata.com> wrote:
> >
> >
> >
> > On Wed, Aug 13, 2025 at 11:52 AM Andrey Borodin <x4mmm@yandex-team.ru> wrote:
> >>
> >> Hi Erik!
> >>
> >> > On 13 Aug 2025, at 11:05, Erik Nordström <erik@tigerdata.com> wrote:
> >> >
> >> > I think I found a small typo in the function that extracts a timestamp from a UUIDv7 (uuid_extract_timestamp). Unless I am mistaken, the constant US_PER_MS should be used instead of NS_PER_US when converting milliseconds to microseconds. Fortunately, these constants are the same so the calculation is still correct.
> >>
> >> Wow, that's a very good level of proofreading! Yes, you are correct, it's must be US_PER_MS.
> >>
> >> >
> >> > Anyway, attaching a patch to fix this typo.
> >>
> >> LGTM.
> >
> >
> > Ok, maybe a committer would like to commit this change immediately?
>
> Thank you for the report! I'll push the patch to master and v18 shortly.

Pushed.

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com