    # File lib/active_record/base.rb, line 689
          def exists?(id_or_conditions = {})
            connection.select_all(
              construct_finder_sql(
                :select     => "#{quoted_table_name}.#{primary_key}",
                :conditions => expand_id_conditions(id_or_conditions),
                :limit      => 1
              ),
              "#{name} Exists"
            ).size > 0
          end