How to set a primary key using Ecto

I had some trouble getting this right and the information across the internet had varrying strategies that often didn’t include all of the details needed to get this right so hopefully this is the answer you’re looking for. In this example I use the primary key :uuid.

To start generate your migration file with mix ecto.gen.migration organizations. From there you will need to include two primary_key keyword list options. The first in the table function and the second in the field function. Example setup:

def change do
  create table("organizations", primary_key: :false) do
    add :name, :string
    add :uuid, :binary_id, primary_key: :true
  end
end

And then in your schema file at lib/organization.ex you will set the schema struct and use the module attributes @primary_key and @foreign_key_type to set the new primary key and foreign key (if needed) data.

@primary_key {:uuid, :binary_id, autogenerate: true}
@foreign_key_type :binary_id
schema "organizations" do
  field :name, :string
end