validate_each

# File activerecord/lib/active_record/validations/uniqueness.rb, line 13
      def validate_each(record, attribute, value)
        finder_class = find_finder_class_for(record)
        table = finder_class.arel_table
        value = map_enum_attribute(finder_class, attribute, value)

        relation = build_relation(finder_class, table, attribute, value)
        relation = relation.and(table[finder_class.primary_key.to_sym].not_eq(record.id)) if record.persisted?
        relation = scope_relation(record, table, relation)
        relation = finder_class.unscoped.where(relation)
        relation = relation.merge(options[:conditions]) if options[:conditions]

        if relation.exists?
          error_options = options.except(:case_sensitive, :scope, :conditions)
          error_options[:value] = value

          record.errors.add(attribute, :taken, error_options)
        end
      end