Ecto.ShortUUID

Ecto.ShortUUID is a custom Ecto.Type which allows for Ecto to automatically encode UUIDs to ShortUUIDs.

ShortUUID is binary-compatible with UUID, so it can be stored in a uuid column in a database.

ShortUUIDs can be used alongside :binary_id or as drop-in replacement for :binary_id primary and foreign keys, basically anywhere Ecto.UUID can be used.

If you're already using :binary_id(Ecto.UUID) for primary keys it is possible to simply switch from :binary_id to using Ecto.ShortUUID and vice versa, neither the underlying data nor DB schema need to be changed.

For example, we can see that calls to Ecto.ShortUUID.dump/1 and Ecto.UUID.dump/1 will return the same binary in the following case:

# let's get the encoded value
iex> Ecto.ShortUUID.cast("2a162ee5-02f4-4701-9e87-72762cbce5e2")
{:ok, "9VprZJ9U7Tgg2PJ8BfTAek"}

# and show off that dump/1 works with both ShortUUIDs and UUIDs
iex> Ecto.ShortUUID.dump("9VprZJ9U7Tgg2PJ8BfTAek")
{:ok, <<42, 22, 46, 229, 2, 244, 71, 1, 158, 135, 114, 118, 44, 188, 229, 226>>}

# dump/1 continues to work with regular UUIDs
iex> Ecto.ShortUUID.dump("2a162ee5-02f4-4701-9e87-72762cbce5e2")
{:ok, <<42, 22, 46, 229, 2, 244, 71, 1, 158, 135, 114, 118, 44, 188, 229, 226>>}

iex> Ecto.UUID.dump("2a162ee5-02f4-4701-9e87-72762cbce5e2")
{:ok, <<42, 22, 46, 229, 2, 244, 71, 1, 158, 135, 114, 118, 44, 188, 229, 226>>}

# when a key is retrieved load/1 is called
# with the binary representation of the UUID 2a162ee5-02f4-4701-9e87-72762cbce5e2
iex> Ecto.ShortUUID.load(<<42, 22, 46, 229, 2, 244, 71, 1, 158, 135, 114, 118, 44, 188, 229, 226>>)
{:ok, "9VprZJ9U7Tgg2PJ8BfTAek"}

# the same binary key continues to work with Ecto.UUID
iex> Ecto.UUID.load(<<42, 22, 46, 229, 2, 244, 71, 1, 158, 135, 114, 118, 44, 188, 229, 226>>)
{:ok, "2a162ee5-02f4-4701-9e87-72762cbce5e2"}

We can see that Ecto.ShortUUID.dump/1 is backwards compatible and still accepts regular UUIDs and the value stored in the DB is exactly the same as when using the regular :binary_id type.

Installation

If available in Hex, the package can be installed by adding ecto_shortuuid to your list of dependencies in mix.exs:

def deps do
  [
    {:ecto_shortuuid, "~> 0.2"}
  ]
end

Example project

You can check out the example project ecto_shortuuid_example with defined config, schemas and seeds to quickly try out ecto_shortuuid for yourself.

Usage

Using Ecto.ShortUUID is similar to using Ecto.UUID.

Schema

You can use the ShortUUID for a regular field

defmodule Post do
  use Ecto.Schema

  schema "posts" do
    field :test, Ecto.ShortUUID
  end
end

To use ShortUUIDs as primary keys we define the @primary_key attribute like this:

defmodule MyApp.User do
  use Ecto.Schema

  @primary_key {:id, Ecto.ShortUUID, autogenerate: true}

  schema "users" do
    field :name, :string
    field :age, :integer, default: 0
    has_many :posts, Post
  end
end

To avoid having to define the primary key type in every schema in case you're using binary ids throughout you can make ShortUUIDs the default by defining the following in the underlying schema module.

# Define a module to be used as base
defmodule MyApp.Schema do
  defmacro __using__(_) do
    quote do
      use Ecto.Schema
      @primary_key {:id, Ecto.ShortUUID, autogenerate: true}
      @foreign_key_type Ecto.ShortUUID
    end
  end
end

# Now use MyApp.Schema to define new schemas
defmodule MyApp.User do
  use MyApp.Schema

  schema "users" do
    field :name, :string
    field :age, :integer, default: 0
    has_many :posts, Post
  end
end

This exactly the same as when using :binary_id as defined in the Ecto docs - Schema attributes.

Migration

The key has to be also defined as :uuid in the migration

defmodule MyApp.Repo.Migrations.CreateUser do
  use Ecto.Migration

  def change do
    create table(:users, primary_key: false) do
      add :id, :uuid, primary_key: true
      add :name, :string
      add :age, :integer
      add :company_id, references(:companies, type: :uuid)

      timestamps
  end
end

Alternatively if starting from scratch you can configure the default migration primary key type as:

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

Read more about config options in the Ecto docs - Repo Configuration.

Documentation

Additional documentation can be found at https://hexdocs.pm/ecto_shortuuid.