class AddRootIdToMemos < ActiveRecord::Migration
  def change
    add_column :memos, :root_id, :integer
    add_index :memos, :root_id

    def get_base_parent comment
      comm = comment
      while comm.parent
        comm = comm.parent
      end
      comm
    end

    count = Memo.all.count / 30 + 2
    transaction do
      for i in 1 ... count do i
      Memo.page(i).per(30).each do |memo|
        unless memo.parent.nil?
          parent = get_base_parent memo
          memo.update_column('root_id', parent.id)
        end
      end
      end
    end
  end
end