Fixed #20272 - Moved update_fields existence check into Model._do_update.

            base_qs = cls._base_manager.using(using)

            values = [(f, None, (getattr(self, f.attname) if raw else f.pre_save(self, False)))

                      for f in non_pks]

            if not values:

                # We can end up here when saving a model in inheritance chain where

                # update_fields doesn't target any field in current model. In that

                # case we just say the update succeeded. Another case ending up here

                # is a model with just PK - in that case check that the PK still

                # exists.

                updated = update_fields is not None or base_qs.filter(pk=pk_val).exists()

            else:

                updated = self._do_update(base_qs, using, pk_val, values)

            updated = self._do_update(base_qs, using, pk_val, values, update_fields)

            if force_update and not updated:

                raise DatabaseError("Forced update did not affect any rows.")

            if update_fields and not updated:

                setattr(self, meta.pk.attname, result)

        return updated

    def _do_update(self, base_qs, using, pk_val, values):

    def _do_update(self, base_qs, using, pk_val, values, update_fields):

        """

        This method will try to update the model. If the model was updated (in

        the sense that an update query was done and a matching row was found

        from the DB) the method will return True.

        """

        if not values:

            # We can end up here when saving a model in inheritance chain where

            # update_fields doesn't target any field in current model. In that

            # case we just say the update succeeded. Another case ending up here

            # is a model with just PK - in that case check that the PK still

            # exists.

            return update_fields is not None or base_qs.filter(pk=pk_val).exists()

        else:

            return base_qs.filter(pk=pk_val)._update(values) > 0

    def _do_insert(self, manager, using, fields, update_pk, raw):