ecto many to many association

gistfile1.ex

defmodule Foo.Model.Job do
  alias Foo.Model.JobToJob, as: JobToJob
  use Ecto.Model

  schema "jobs" do
    field :name, :string
    has_many :children, JobToJob, foreign_key: :parent_id
    has_many :parents, JobToJob, foreign_key: :child_id
  end
end

defmodule Foo.Model.JobToJob do
  alias Foo.Model.Job, as: Job
  use Ecto.Model

  schema "job_to_job", primary_key: false do
    belongs_to :parent, Job, foreign_key: :parent_id
    belongs_to :child, Job, foreign_key: :child_id
  end
end

job1 = %Job{name: "parent"} |> Repo.insert
job2 = %Job{name: "child2"} |> Repo.insert
jobToJob = %JobToJob{parent: job1, child: job2}
jobToJob = Repo.insert(jobToJob)