def concat(*records)
      load_target
      flatten_records = records.flatten
      flatten_records.each { |val| raise_on_type_mismatch!(val) }
      target_ids = reflection.options[:target_ids]
      owner[target_ids] ||= []
      owner[target_ids].concat(flatten_records.map(&:id))

      flatten_records.each do |record|
        if index = @target.index(record)
          @target[index] = record
        else
          @target << record
        end
      end

      target
    end
def concat(*records)
      load_target
      flatten_records = records.flatten
      flatten_records.each { |val| raise_on_type_mismatch!(val) }
      target_ids = reflection.options[:target_ids]
      owner[target_ids] ||= []
      owner[target_ids].concat(flatten_records.map(&:id))

      flatten_records.each do |record|
        if index = @target.index(record)
          @target[index] = record
        else
          @target << record
        end
      end

      target
    end
no need transaction