Add an association with composite primary key

integration_test/support/migration.exs

@@ -27,6 +27,8 @@ defmodule Ecto.Integration.Migration do
       add :intensity, :float
       add :author_id, :integer
       add :posted, :date
+      add :composite_a, :integer
+      add :composite_b, :integer
       timestamps(null: true)
     end
 
@@ -108,6 +110,11 @@ defmodule Ecto.Integration.Migration do
       add :name, :string
     end
 
+    # TODO not sure if it is important to have a foreign keys defined properly; see other associations in "posts"
+    alter table(:posts) do
+      modify :composite_a, references(:composite_pk, column: :a, with: [composite_b: :b], type: :integer)
+    end
+
     create table(:corrupted_pk, primary_key: false) do
       add :a, :string
     end