"Other people" think that extracting the timestamp from UUIDv7 in violation of
the new RFC, and generating UUIDv7 from the timestamp were both terrible and
poorly thought out ideas. The authors of the new RFC had very good reasons to
prohibit this. And the problems you face are the best confirmation of the
correctness of the new RFC. It’s better to throw all this gag out of the
official patch. Don't tempt developers to break the new RFC with these
error-producing functions.
Sergey prokhorenkosergeyprokhore...@yahoo.com.au
On Wednesday, 24 January 2024 at 04:30:02 pm GMT+3, Aleksander Alekseev
<aleksan...@timescale.com> wrote:
Hi,
> Function to extract timestamp does not provide any guarantees at all.
> Standard states this, see Kyzer answers upthread.
> Moreover, standard urges against relying on that if uuidX was generated
> before uuidY, then uuidX<uuid. The standard is doing a lot to make this
> happen, but does not guaranty that.
> All what is guaranteed is the uniqueness at certain conditions.
>
> > Otherwise you can calculate crc64(X) or sha256(X)
> > internally in order to generate an unique ID and claim that it's fine.
> >
> > Values that violate named invariants should be rejected with an error.
>
> Think about the value that you pass to uuid generation function as an
> entropy. It’s there to ensure uniqueness and promote ordering (but not
> guarantee).
If the standard doesn't guarantee something it doesn't mean it forbids
us to give stronger guarantees. I'm convinced that these guarantees
will be useful in real-world applications, at least the ones acting
exclusively within Postgres.
This being said, I understand your point of view too. Let's see what
other people think.
--
Best regards,
Aleksander Alekseev
