Re: UUID v7

First of all, I'm a huge fan of UUID v7. So I'm very excited that this
is progressing. I'm definitely going to look closer at this patch
soon. Some tiny initial feedback:

(bikeshed) I'd prefer renaming `get_uuid_v7_time` to the shorter
`uuid_v7_time`, the `get_` prefix seems rarely used in Postgres
functions (e.g. `date_part` is not called `get_date_part`). Also it's
visually very similar to the gen_ prefix.

On Thu, 4 Jan 2024 at 19:20, Andrey M. Borodin <x4mmm@yandex-team.ru> wrote:
> > On 3 Jan 2024, at 04:37, Przemysław Sztoch <przemyslaw@sztoch.pl> wrote:
> > 1. Is it possible to add a function that returns the version of the generated uuid?
> > It will be very useful.
> > I don't know if it's possible, but I think there are bits in the UUID that inform about the version.
> What do you think if we have functions get_uuid_v7_ver(uuid) and get_uuid_v7_var(uuid) to extract bit fields according to [0] ? Or, perhaps, this should be one function with two return parameters?
> It's not in a patch yet, I'm just considering how this functionality should look like.

I do agree that those functions would be useful, especially now that
we're introducing a function that errors when it's passed a UUID
that's not of version 7. With the version extraction function you
could return something else for other uuids if you have many and not
all of them are version 7.

I do think though that these functions should not have v7 in their
name, since they would apply to all uuids of all versions (so if also
removing the get_ prefix they would be called uuid_ver and uuid_var)

> > 4. Sometimes you will need to generate a uuid for historical time. There should be an additional function gen_uuid_v7(timestamp).
> Done, please see patch attached. But I changed signature to gen_uuid_v7(int8), to avoid messing with bytes from user who knows what they want. Or do you think gen_uuid_v7(timestamp) would be more convenient?

I think timestamp would be quite useful. timestamp would encode the
time in the same way as gen_uuid_v7() would, but based on the given
time instead of the current time.