Return Ecto query tuple as json in Phoenix

I’m having some issues with my Json API and Ecto. I’m getting a bunch of data from the database with the following code:

    query = from message in "messages",
      where: ^id == message.room,
      select: {message.message, message.id, message.room}
    messages = Repo.all(query)

I then pass these messages into a view function and run through it with the following code:

  def render("chat.json", %{messages: messages}) do
    Enum.each(messages, fn message ->
      render(ChatView, "message.json", message: message)
    end)
  end

In the message.json function I’m trying to print out the three selected fields, which as faar as I understand are in a query:

  def render("message.json", %{message: message}) do
    %{
      message: elem(message, 0),
      id: elem(message, 1),
      room: elem(message, 2)
    }
  end

If I print out the message in the render function, it prints out the corrent content. But the code above simple returns “ok” without any other content or errors.
What am I doing wrong?