UUIDs with Ecto

20171001010000_add_uuid_ossp.exs

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

  def up do
    execute("CREATE EXTENSION IF NOT EXISTS \"uuid-ossp\" WITH SCHEMA public;")
  end

  def down do
    execute("DROP EXTENSION \"uuid-ossp\";")
  end
end

20171001010001_add_model.exs

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

  def change do
    create table(:model, primary_key: false) do
      add(:id, :uuid, primary_key: true, default: fragment("uuid_generate_v4()"))
      timestamps()
    end
  end
end

model.ex

defmodule MyApp.Model do
  use MyApp, :model

  schema "model" do
    timestamps()
  end
end

my_app.ex

defmodule MyApp do
  def model do
    quote do
      use Ecto.Schema

      import Ecto
      import Ecto.Changeset

      @primary_key {:id, :binary_id, autogenerate: false, read_after_writes: true}
      @foreign_key_type :binary_id
    end
  end

  defmacro __using__(which) when is_atom(which) do
    apply(__MODULE__, which, [])
  end
end