ash_postgres/lib/manual_relationship.ex

defmodule AshPostgres.ManualRelationship do
  @moduledoc "A behavior for postgres-specific manual relationship functionality"

  @callback ash_postgres_join(
              source_query :: Ecto.Query.t(),
              opts :: Keyword.t(),
              current_binding :: term,
              destination_binding :: term,
              type :: :inner | :left,
              destination_query :: Ecto.Query.t()
            ) :: {:ok, Ecto.Query.t()} | {:error, term}

  @callback ash_postgres_subquery(
              opts :: Keyword.t(),
              current_binding :: term,
              destination_binding :: term,
              destination_query :: Ecto.Query.t()
            ) :: {:ok, Ecto.Query.t()} | {:error, term}

  defmacro __using__(_) do
    quote do
      @behaviour AshPostgres.ManualRelationship
    end
  end
end