Ulid VS spec

Side note, an interesting thing to add to your benchmarks would be ULID https://github.com/Cysharp/Ulid

I’m using Postgres so I actually have it a little easier with its native sort order. I switched from NUlid that I was using from years back to this one [0], and the default .ToGuid() gets the desired sort order when used with Npgsql. Likewise though, no db-side generation of uuid - then again, isn’t that the benefit of using globally unique identifiers in the first place, to avoid needing to rely on the db to generate conflict-free identifiers, skipping HiLo or sequences, etc.

Anyway, nice to meet another .NET Ulid user in the wild!

0: https://github.com/Cysharp/Ulid

Can use ULID to "fix" some issues

https://github.com/ulid/spec

Both ULID and UUID v7 have a time code component which can be extracted.

It would be best for indexing to store the actual value in binary, though not strictly necessary as these later UUID standards (unlike conventional UUIDs) use time code prefixes (so indexing clusters.)

https://uuid7.com/

https://github.com/ulid/spec

UUIDv7 is a nice idea, and should probably be what people use by default instead of UUIDv4.

For the curious:

* UUIDv4 are 128 bits long, 122 bits of which are random, with 6 bits used for the version. Traditionally displayed as 32 hex characters with 4 dashes, so 36 alphanumeric characters, and compatible with anything that expects a UUID.

* UUIDv7 are 128 bits long, 48 bits encode a unix timestamp with millisecond precision, 6 bits are for the version, and 74 bits are random. You're expected to display them the same as other UUIDs, and should be compatible with basically anything that expects a UUID. (Would be a very odd system that parses a UUID and throws an error because it doesn't recognise v7, but I guess it could happen, in theory?)

* ULIDs (https://github.com/ulid/spec) are 128 bits long, 48 bits encode a unix timestamp with millisecond precision, 80 bits are random. You're expected to display them in Crockford's base32, so 26 alphanumeric characters. Compatible with almost everything that expects a UUID (since they're the right length). Spec has some dumb quirks if followed literally but thankfully they mostly don't hurt things.

* KSUIDs (https://github.com/segmentio/ksuid) are 160 bits long, 32 bits encode a timestamp with second precision and a custom epoch of May 13th, 2014, and 128 bits are random. You're expected to display them in base62, so 27 alphanumeric characters. Since they're a different length, they're not compatible with UUIDs.

I quite like KSUIDs; I think base62 is a smart choice. And while the timestamp portion is a trickier question, KSUIDs use 32 bits which, with second precision (more than good enough), means they won't overflow for well over a century. Whereas UUIDv7s use 48 bits, so even with millisecond precision (not needed) they won't overflow for something like 8000 years. We can argue whether 100 years us future proof enough (I'd argue it probably is), but 8000 years is just silly. Nobody will ever generate a compliant UUIDv7 with any of the first several bits aren't 0. The only downside to KSUIDs is the length isn't UUID compatible (and arguably, that they don't devote 6 bits to a compliant UUID version).

Still feels like there's room for improvement, but for now I think I'd always pick UUIDv7 over UUIDv4 unless there's an very specific reason not to.

I'd love for Postgres to adopt ULID as a first class variant of the same basic 128bit wide binary optimized column type they use for UUIDs, but I don't expect they will, while its "popular" its not likely popular enough to have support for them to maintain it in the long run... Also the smart money ahead of time would have been for the ULID spec to sacrifice a few data bits to leave the version specifying sections of the bit field layout unused in the ULID binary spec (https://github.com/ulid/spec#binary-layout-and-byte-order) for the sake of future compatibility with "proper" UUIDs... Performing one big bulk bitfield modification to a PostgreSQL column would have been much less painful than re-computing appropriate UUIDv7 (or UUIDv8s for some reason) and then having to perform a primary key update on every row in the table.

Many people had the same idea. For example ULID https://github.com/ulid/spec is more compact and stores the time so it is lexically ordered.