Using UUIDs as primary key with Ecto

create_post.exs

defmodule MyBlog.Repo.Migrations.CreatePost do
  use Ecto.Migration

  def change do
    create table(:posts, primary_key: false) do
      add :id, :uuid, primary_key: true
      add :body, :string
      add :word_count, :integer

      timestamps
    end
  end
end

post.ex

defmodule MyBlog.Post do
  use MyBlog.Web, :model
  
  @primary_key {:id, :binary_id, autogenerate: true}

  schema "posts" do
    field :body, :string
    field :word_count, :integer

    timestamps
  end

  @required_fields ~w(body word_count)
  @optional_fields ~w()

  @doc """
  Creates a changeset based on the `model` and `params`.

  If `params` are nil, an invalid changeset is returned
  with no validation performed.
  """
  def changeset(model, params \\ nil) do
    model
    |> cast(params, @required_fields, @optional_fields)
  end
end