class DeleteNullAtMessages < ActiveRecord::Migration
  def up
    count = AtMessage.all.count / 30 + 2
    transaction do
      for i in 1 ... count do i
      AtMessage.page(i).per(30).each do |am|
        if am.at_message.nil?
          am.destroy
        end
      end
      end
    end
  end

  def down
  end
end