ExULID

Universally Unique Lexicographically Sortable Identifier (ULID) in Elixir. Implemented according to ulid/spec.

Why ULID?

UUID can be suboptimal for many uses-cases because:

• It isn't the most character efficient way of encoding 128 bits of randomness
• UUID v1/v2 is impractical in many environments, as it requires access to a unique, stable MAC address
• UUID v3/v5 requires a unique seed and produces randomly distributed IDs, which can cause fragmentation in many data structures
• UUID v4 provides no other information than randomness which can cause fragmentation in many data structures

Instead, herein is proposed ULID:

• 128-bit compatibility with UUID
• 1.21e+24 unique ULIDs per millisecond
• Lexicographically sortable!
• Canonically encoded as a 26 character string, as opposed to the 36 character UUID
• Uses Crockford's base32 for better efficiency and readability (5 bits per character)
• Case insensitive
• No special characters (URL safe)
• Monotonic sort order (correctly detects and handles the same millisecond)

Goodies that comes with this libraries

• It uses binary operations (so it's super fast!)
• It can decode the timestamp back from the ULID
• It includes tests from other language's implementations, ensuring the consistency & correctness of the ULID produced.

Installation

Add ExULID as a dependency in your project's mix.exs:

def deps do
  [
    {:ex_ulid, "~> 0.1.0"}
  ]
end

Then run mix deps.get to resolve and install it.

Usage

Generate a ULID with the current time:

ExULID.ULID.generate()
#=> "01C9GJZZ3D530PE8Q0ZYV5HJ9K"

Generate a ULID for a specific time:

ExULID.ULID.generate(1469918176385)
#=> "01ARYZ6S41QJQECH4KPG6SEF3Y"

Decode the ULID back to get the timestamp and randomness:

ExULID.ULID.decode("01ARYZ6S41QJQECH4KPG6SEF3Y")
#=> {1469918176385, "QJQECH4KPG6SEF3Y"}

Benchmark

$ mix run bench/run.exs
Operating System: macOS
CPU Information: Intel(R) Core(TM) i5-7360U CPU @ 2.30GHz
Number of Available Cores: 4
Available memory: 16 GB
Elixir 1.6.4
Erlang 20.2.4
Benchmark suite executing with the following configuration:
warmup: 2 s
time: 5 s
parallel: 1
inputs: none specified
Estimated total run time: 7 s

Benchmarking encode...

Name             ips        average  deviation         median         99th %
encode       52.08 K       19.20 μs   ±116.33%          16 μs          60 μs


Operating System: macOS
CPU Information: Intel(R) Core(TM) i5-7360U CPU @ 2.30GHz
Number of Available Cores: 4
Available memory: 16 GB
Elixir 1.6.4
Erlang 20.2.4
Benchmark suite executing with the following configuration:
warmup: 2 s
time: 5 s
parallel: 1
inputs: none specified
Estimated total run time: 7 s

Benchmarking decode...

Name             ips        average  deviation         median         99th %
decode       18.86 K       53.03 μs    ±24.71%          50 μs         100 μs

TODO

• Monotonicity generator

License

ExULID is released under the Apache License.