text: class MoveNotificationsOntoConference < ActiveRecord::Migration[4.2]
    def change
      add_column :notifications, :conference_id, :integer
      Notification.find_each { |n|
        next unless n.call_for_papers_id
        execute %(UPDATE notifications SET conference_id=(SELECT conference_id FROM call_for_papers AS cfp WHERE cfp.id=#{n.call_for_papers_id}) WHERE id=#{n.id};)
      }
      remove_column :notifications, :call_for_papers_id
    end
  end
  