owner_keys

# File activerecord/lib/active_record/associations/preloader/association.rb, line 71
        def owner_keys
          unless defined?(@owner_keys)
            @owner_keys = owners.map do |owner|
              owner[owner_key_name]
            end
            @owner_keys.uniq!
            @owner_keys.compact!
          end
          @owner_keys
        end