UUIDv7 for Elixir and (optionally) Ecto, using an 18-bit randomly-seeded counter.

Uses suggestions described in Section 6.2 from this IETF Draft to add additional sort precision to a version 7 UUID.

• You want sequential, time-based, ordered IDs (per-node).
• You are willing to trade a small amount of raw performance for these guarantees. You are taking a hit for the counter with rollover protection, and backwards time-leap protection.

NOTE: In this library, sequential UUIDs and ordering are more important than time precision and performance. We take a slight hit in both of those areas to ensure that the UUIDs are in order. For example, in the case of a backwards time leap, we continue with the previously used timestamp, and in the case of rollover, we increment the timestamp by one to ensure that the ordering is maintained.

• You don't care about sort/order precision beyond milliseconds.

There are other UUID packages, that only have millisecond precision, for example:

• martinthenth/uuidv7
• bitwalker/uniq

The package can be installed by adding uuid_v7 to your list of dependencies in mix.exs:

def deps do
  [
    {:uuid_v7, "~> 0.5.0"}
  ]
end

iex> UUIDv7.generate()
"018e90d8-06e8-7f9f-bfd7-6730ba98a51b"

iex> UUIDv7.bingenerate()
<<1, 142, 144, 216, 124, 16, 127, 196, 158, 92, 92, 74, 83, 46, 116, 173>>

Use this the same way you would use Ecto.UUID. For example:

defmodule MyApp.Blog.Post do
  use Ecto.Schema

  @primary_key {:id, UUIDv7.Type, autogenerate: true}

  @foreign_key_type UUIDv7.Type

  schema "blog_posts" do
    field :text, :string
    # etc.
  end
end

To use UUIDs for everything in your migrations, it's easiest to just add that as the default type in your config.exs. e.g.:

config :app, App.Repo,
  migration_primary_key: [type: :binary_id],
  migration_foreign_key: [type: :binary_id]

Run benchmarks with

MIX_ENV=bench mix run bench/filename.exs

Where filename.exs is the name of one of the benchmark files in the bench directory.

(which has no counter or time-leap protection. millisecond precision.)

Name                     ips        average  deviation         median         99th %
uniq v7 string        2.23 M      448.71 ns  ±3082.24%         417 ns         583 ns
uuid_v7 string        2.08 M      480.89 ns  ±3868.08%         417 ns         625 ns

Comparison:
uniq v7 string        2.23 M
uuid_v7 string        2.08 M - 1.07x slower +32.18 ns

Name                  ips        average  deviation         median         99th %
uniq v7 raw        3.35 M      298.15 ns  ±7140.23%         250 ns         375 ns
uuid_v7 raw        2.71 M      368.53 ns  ±4920.92%         333 ns         459 ns

Comparison:
uniq v7 raw        3.35 M
uuid_v7 raw        2.71 M - 1.24x slower +70.37 ns