Rails 3 - select random record(s)

random_record.rb

module RandomRecord
  def random
    order(random_function_name)    
  end
  
  private
  def random_function_name
    if !defined? @__random_function_name
      @__random_function_name = "rand()" 
      begin
        connection.execute("select #{@__random_function_name}") 
      rescue ActiveRecord::StatementInvalid 
        @__random_function_name = "random()"
      end
    end
    @__random_function_name
  end
end

ActiveRecord::Base.extend RandomRecord if defined? ActiveRecord::Base