scope_relation

# File activerecord/lib/active_record/validations/uniqueness.rb, line 134
      def scope_relation(record, relation)
        Array(options[:scope]).each do |scope_item|
          scope_value = if record.class._reflect_on_association(scope_item)
            record.association(scope_item).reader
          else
            record.read_attribute(scope_item)
          end
          relation = relation.where(scope_item => scope_value)
        end

        relation
      end