discourse/db/migrate/20121122033316_add_muted_at_to_topic_user.rb

class AddMutedAtToTopicUser < ActiveRecord::Migration
  def change
    add_column :topic_users, :muted_at, :datetime
    change_column :topic_users, :last_read_post_number, :integer, :null => true
    change_column_default :topic_users, :last_read_post_number, nil
  end
end