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An Ecto.Type implementation of ULID.

Ecto.ULID should be compatible anywhere that Ecto.UUID is supported. It has been confirmed to work with PostgreSQL and MySQL on Ecto 2.x and 3.x. Ecto 1.x is not supported.

ULID is a 128-bit universally unique lexicographically sortable identifier. ULID is binary-compatible with UUID, so it can be stored in a uuid column in a database.


  • Generate ULID in Base32 or binary format.
  • Generate ULID for a given timestamp.
  • Autogenerate ULID when used as a primary key.
  • Supports reading and writing ULID in a database backed by its native uuid type (no database extensions required).
  • Supports Ecto 2.x and Ecto 3.x.
  • Supports Elixir 1.4 and newer.
  • Confirmed working on PostgreSQL and MySQL.
  • Optimized for high throughput.


Since one use case of ULID is to handle a large volume of events, Ecto.ULID is optimized to be as fast as possible. It borrows techniques from Ecto.UUID to achieve sub-microsecond times for most operations.

A benchmark suite is included. Download the repository and run mix bench to test the performance on your system.

The following are results from running the benchmark on an AMD Ryzen Threadripper 1950X:

benchmark name iterations   average time
cast/1           10000000   0.25 µs/op
dump/1           10000000   0.50 µs/op
load/1           10000000   0.55 µs/op
bingenerate/0    10000000   0.93 µs/op
generate/0        1000000   1.55 µs/op


Usage is very similar to Ecto.UUID. The following example shows how to use Ecto.ULID as a primary key in a database table, but it can be used for other columns just as easily.

API documentation is available on hexdocs.


Install ecto_ulid from Hex by adding it to the dependencies in mix.exs:

defp deps do
    {:ecto_ulid, "~> 0.2.0"}


Since ULID is binary-compatible with UUID, the migrations look the same for both types. Use :binary_id when defining a column in a migration:

create table(:events, primary_key: false) do
  add :id, :binary_id, null: false, primary_key: true
  # more columns ...

Alternatively, if you plan to use ULID as the primary key type for all of your tables, you can set migration_primary_key when configuring your Repo:

config :my_app, MyApp.Repo, migration_primary_key: [name: :id, type: :binary_id]

and then you do not need to specify the id column in your migrations:

create table(:events) do
  # more columns ...


When defining a model's schema, use Ecto.ULID as the @primary_key or @foreign_key_type as appropriate for your schema. Here's an example of using both:

defmodule MyApp.Event do
  use Ecto.Schema

  @primary_key {:id, Ecto.ULID, autogenerate: false}
  @foreign_key_type Ecto.ULID
  schema "events" do
    # more columns ...

Ecto.ULID supports autogenerate: true as well as autogenerate: false when used as the primary key.

#Application Usage

A ULID can be generated in string or binary format by calling generate/0 or bingenerate/0. This can be useful when generating ULIDs to send to external systems:

Ecto.ULID.generate()    #=> "01BZ13RV29T5S8HV45EDNC748P"
Ecto.ULID.bingenerate() #=> <<1, 95, 194, 60, 108, 73, 209, 114, 136, 236, 133, 115, 106, 195, 145, 22>>

To backfill old data, it may be helpful to pass a timestamp to generate/1 or bingenerate/1. See the API documentation for more details.


Copyright © 2018 The RealReal, Inc.

Distributed under the MIT License.