use Model.reset_column_information to let the modification work, and use say_with_time to explain the action..

add_column_migration.rb

class AddAddressToEvent < ActiveRecord::Migration
  def up
    add_column :events, :address, :string, :after => :lat

    Event.reset_column_information

    say_with_time "Update each event, which will result in all events to update their address" do
      Event.find_each { |event| event.save! }
    end
  end

  def down
    remove_column :events, :address
  end
end