Method prefetch_related

tortoise/queryset.py:1016–1043

Like ``.fetch_related()`` on instance, but works on all objects in QuerySet. :raises FieldError: If the field to prefetch on is not a relation, or not found.

(self, *args: str | Prefetch)

        return self

    def prefetch_related(self, *args: str | Prefetch) -> QuerySet[MODEL]:
        """
        Like ``.fetch_related()`` on instance, but works on all objects in QuerySet.

        :raises FieldError: If the field to prefetch on is not a relation, or not found.
        """
        queryset = self._clone()
        queryset._prefetch_map = {}

        for relation in args:
            if isinstance(relation, Prefetch):
                relation.resolve_for_queryset(queryset)
                continue

            first_level_field, __, forwarded_prefetch = relation.partition("__")
            if first_level_field not in self.model._meta.fetch_fields:
                if first_level_field in self.model._meta.fields:
                    raise FieldError(
                        f"Field {first_level_field} on {self.model._meta.full_name} is not a relation"
                    )
                raise FieldError(
                    f"Relation {first_level_field} for {self.model._meta.full_name} not found"
                )
            if first_level_field not in queryset._prefetch_map.keys():
                queryset._prefetch_map[first_level_field] = set()
            if forwarded_prefetch:
                queryset._prefetch_map[first_level_field].add(forwarded_prefetch)
        return queryset

    async def explain(self) -> Any:
        """Fetch and return information about the query execution plan.