Support counters in v7 UUIDs #755

2024-05-12T22:25:51-05:00

KodrAus commented

2024-05-12 22:25:51 -05:00

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This PR sketches out a solution to make the v7 support respect the input counter, while retaining existing semantics around filling with random data. It requires a bit of fudgery to keep compatibility with existing APIs, but I think the overall solution works out ok. I need to actually fill it all in fully and then explore ways to better integrate the existing Timestamp API, which may involve deprecating bits.

The gist of it is to add a usable_bits method to ClockSequence, so it can tell how many bits a given counter occupies. The UUID constructor can then do appropriate shifts and fill the rest with random bytes. That way a caller creating a v7 UUID can decide how many bits to dedicate to sequencing and how many to randomness.

As part of this PR I'm expecting to find some solution to re-seeding sequences, which will probably remain an implementation detail of the given ClockSequence.

For #717 This PR sketches out a solution to make the v7 support respect the input counter, while retaining existing semantics around filling with random data. It requires a bit of fudgery to keep compatibility with existing APIs, but I think the overall solution works out ok. I need to actually fill it all in fully and then explore ways to better integrate the existing `Timestamp` API, which may involve deprecating bits. The gist of it is to add a `usable_bits` method to `ClockSequence`, so it can tell how many bits a given counter occupies. The UUID constructor can then do appropriate shifts and fill the rest with random bytes. That way a caller creating a v7 UUID can decide how many bits to dedicate to sequencing and how many to randomness. As part of this PR I'm expecting to find some solution to re-seeding sequences, which will probably remain an implementation detail of the given `ClockSequence`.

KodrAus (Migrated from github.com) reviewed

2024-05-13 17:34:53 -05:00

src/timestamp.rs

					
				@ -358,0 +475,4 @@

				        /// to adjust the timestamp on overflow.

				        #[derive(Debug)]

				        pub struct Context {

				            count: Atomic<u16>,

We need to add another implementation here with a 42bit counter that's intended to be used by v7 UUIDs.

KodrAus (Migrated from github.com) reviewed

2024-05-13 17:35:49 -05:00

src/v7.rs

These examples should use Timestamp::from_unix_wide with a 42bit counter to steer users wanting counters in the right direction.

These examples should use `Timestamp::from_unix_wide` with a 42bit counter to steer users wanting counters in the right direction.

KodrAus commented

2024-06-19 18:19:43 -05:00

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I've got a counter implemented, but looks like performance here could use some improvement compared to uuid7:

running 2 tests
test new_v4   ... bench:          24.69 ns/iter (+/- 0.43)
test uuid7_v4 ... bench:          14.31 ns/iter (+/- 0.06)

test now_v7   ... bench:          56.86 ns/iter (+/- 1.04)
test uuid7_v7 ... bench:          38.03 ns/iter (+/- 0.59)

I've got a counter implemented, but looks like performance here could use some improvement compared to [`uuid7`](https://github.com/LiosK/uuid7-rs): ``` running 2 tests test new_v4 ... bench: 24.69 ns/iter (+/- 0.43) test uuid7_v4 ... bench: 14.31 ns/iter (+/- 0.06) test now_v7 ... bench: 56.86 ns/iter (+/- 1.04) test uuid7_v7 ... bench: 38.03 ns/iter (+/- 0.59) ```

KodrAus commented

2024-06-19 19:32:43 -05:00

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Ok, I think that's better now:

test new_v4   ... bench:           8.35 ns/iter (+/- 0.34)
test uuid7_v4 ... bench:          14.38 ns/iter (+/- 0.78)

test now_v7   ... bench:          36.51 ns/iter (+/- 2.60)
test uuid7_v7 ... bench:          38.31 ns/iter (+/- 2.35)

Ok, I think that's better now: ``` test new_v4 ... bench: 8.35 ns/iter (+/- 0.34) test uuid7_v4 ... bench: 14.38 ns/iter (+/- 0.78) test now_v7 ... bench: 36.51 ns/iter (+/- 2.60) test uuid7_v7 ... bench: 38.31 ns/iter (+/- 2.35) ```

KodrAus commented

2024-06-19 20:05:14 -05:00

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