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help / color / mirror / Atom feedFrom: Christophe Pettus <[email protected]>
To: Andrey Borodin <[email protected]>
Cc: [email protected]
Subject: Re: uuidv7 improperly accepts dates before 1970-01-01
Date: Mon, 27 Apr 2026 15:51:12 -0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
<[email protected]>
Hi, Andrey,
Thanks for the response! I'm moving it to -hackers since it's not really a bug related conversation at this point. (resending with the right list this time!)
> On Apr 25, 2026, at 05:26, Andrey Borodin <[email protected]> wrote:
> We consulted with RFC authors
> about this feature, and they confirmed that shifting time is compliant with RFC wording.
Time shifting doesn't automatically imply allowing a pre-epoch input time to construct a UUIDv7, though, just that you can construct a UUIDv7 with something other than wall-clock time.
> We wrote the specific test that ensures vast space for shift, but not unlimited.
That's another problem: the API gives the impression of a much larger space than actually exists.
# select uuidv7('100000 years'::interval); # ~11.2 x total time range in a UUID v7.
uuidv7
--------------------------------------
37b45c74-469d-7e1b-9397-1a971a99ab2b
(1 row)
At a minimum, it should reject a shift that creates a time later than a UUID v7 can represent.
> Time shifting would become a footgun if we throw an exception when overflown.
I don't understand why. If the concern is that someone will pick a value that's close to the maximum, and get a surprising exception when the time overflows that, the right answer is to caution them not to do that rather than permit the wraparound.
And is anyone actually doing this? Using a very large interval with a large enough number of shards that wraparound is a real possibility? (In that case, I'd argue they should construct the 48 bit field directly rather than kind of dancing around it by using a time shift.)
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To: [email protected]
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Subject: Re: uuidv7 improperly accepts dates before 1970-01-01
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