mongo_solr_adapter.rb

module MongoAdapter
  class InstanceAdapter < Sunspot::Adapters::InstanceAdapter
    def id
      @instance.id
    end
  end

  class DataAccessor < Sunspot::Adapters::DataAccessor
    def load(id)
      @clazz.find(id)
    end

    # def load_all(ids)
    #   @clazz.find_all_by_id(ids)
    # end
  end
end

Sunspot::Adapters::DataAccessor.register(MongoAdapter::DataAccessor, User)
Sunspot::Adapters::InstanceAdapter.register(MongoAdapter::InstanceAdapter, User)