ksuid VS pg-ulid

OP here - we avoid sequences in all but one part of our application due to a dependency. We use [KSUIDs][1] and UUID v4 in various places. This one "gotcha" applies to any sequence, so it's worth calling out as general advice when running a migration like this.

[1]: https://segment.com/blog/a-brief-history-of-the-uuid/

UUID v4 isn't large enough to prevent collisions, that is why segment.io created https://github.com/segmentio/ksuid which is 160bit vs the 128bit of a UUIDv4.

Assuming you don't need to use UUIDv7 (or any UUID's) then https://github.com/segmentio/ksuid provides a much bigger keyspace. You could just append a string prefix if you wanted to namespace, but the chance of collisions of a KSUID is many times smaller than a UUID of any version.

KSUID's are have temporal-lexicographical order plus 128 bits of entropy, which is more than UUIDv4.

https://github.com/segmentio/ksuid

That's why you use ksuid (https://segment.com/blog/a-brief-history-of-the-uuid/) or, if you're willing to go with a draft spec you could go with the new UUID formats https://www.ietf.org/archive/id/draft-ietf-uuidrev-rfc4122bi...

Interesting in more history of UUIDs? Twilio Segment's blog has an amazing history lesson about how they came to be.

I use the ksuid from segment. https://github.com/segmentio/ksuid

Here's one[1], not actively maintained though.

[1] https://github.com/edoceo/pg-ulid

Yeah, just use a UUID unless the bits to store the UUID really are your driving limitation (they're not), having a UUID that is non-linear is almost always the most straight-forward option for identifying things, for the tradeoff of human readability (though you can get some of that back with prefixes and some other schemes). I'm not going to rehash the benefits that people have brought up for UUIDs, but they're in this thread. At this point what I'm concerned about is just... what is the best kind of UUID to use -- I've recently started using mostly v1 because time relationship is important to me (despite the unfortunate order issues) and v6[0] isn't quite so spread yet. Here's a list of other approaches out there worth looking at

- isntauuid[1] (mentioned in this thread, I've given it a name here)

- timeflake[2]

- HiLo[3][4]

- ulid[5]

- ksuid[6] (made popular by segment.io)

- v1-v6 UUIDs (the ones we all know and some love)

- sequential interval based UUIDs in Postgres[7]

Just add a UUID -- this almost surely isn't going to be what bricks your architecture unless you have some crazy high write use case like time series or IoT or something maybe.

[0]: http://gh.peabody.io/uuidv6/

[1]: https://instagram-engineering.com/sharding-ids-at-instagram-...

[2]: https://github.com/anthonynsimon/timeflake

[3]: https://en.wikipedia.org/wiki/Hi/Lo_algorithm

[4]: https://www.npgsql.org/efcore/modeling/generated-properties....

[5]: https://github.com/edoceo/pg-ulid

[6]: https://github.com/segmentio/ksuid

[7]: https://www.2ndquadrant.com/en/blog/sequential-uuid-generato...