Ecto Many to Many

migration.exs

def change do
	# indices omitted

	create table(:products) do
		add(:name, :string)
	end

	create table(:product_attributes) do
		add(:property, :json)
		add(:product_type_id, :id)
	end

	create table(:products_product_attributes) do
		add(:product_id)
		add(:product_attribute_id)
	end

	create table(:product_types) do
		add(:name, :string)
	end
end

product.ex

schema "products" do
	field(:name, :string)
	many_to_many(:product_attributes, MyApp.ProductAttribute,
		join_through: MyApp.ProductsProductAttribute
	)
end

product_attribute.ex

schema "product_attributes" do
	field(:property, :json)
	has_one(MyApp.ProductType)
end

product_type.ex

schema "product_type" do
	field(:name, :string)
end

products_product_attributes.ex

schema "product_product_attributes" do
	belongs_to(:product, MyApp.Product)
	belongs_to(:product_attribute, MyApp.ProductAttribute)
end