instance method migrate

# File activerecord/lib/active_record/migration.rb, line 366
    def migrate(direction)
      return unless respond_to?(direction)

      case direction
      when :up   then announce "migrating"
      when :down then announce "reverting"
      end

      time   = nil
      ActiveRecord::Base.connection_pool.with_connection do |conn|
        @connection = conn
        if respond_to?(:change)
          if direction == :down
            recorder = CommandRecorder.new(@connection)
            suppress_messages do
              @connection = recorder
              change
            end
            @connection = conn
            time = Benchmark.measure {
              recorder.inverse.each do |cmd, args|
                send(cmd, *args)
              end
            }
          else
            time = Benchmark.measure { change }
          end
        else
          time = Benchmark.measure { send(direction) }
        end
        @connection = nil
      end

      case direction
      when :up   then announce "migrated (%.4fs)" % time.real; write
      when :down then announce "reverted (%.4fs)" % time.real; write
      end
    end