Class Prefetch

tortoise/query_utils.py:233–274

Prefetcher container. One would directly use this when wanting to attach a custom QuerySet for specialised prefetching. :param relation: Related field name. :param queryset: Custom QuerySet to use for prefetching. :param to_attr: Sets the result of the prefetch operation to a c

class Prefetch:
    """
    Prefetcher container. One would directly use this when wanting to attach a custom QuerySet
    for specialised prefetching.

    :param relation: Related field name.
    :param queryset: Custom QuerySet to use for prefetching.
    :param to_attr: Sets the result of the prefetch operation to a custom attribute.
    """

    __slots__ = ("relation", "queryset", "to_attr")

    def __init__(self, relation: str, queryset: QuerySet, to_attr: str | None = None) -> None:
        self.to_attr = to_attr
        self.relation = relation
        self.queryset = queryset
        self.queryset.query = copy(self.queryset.model._meta.basequery)

    def resolve_for_queryset(self, queryset: QuerySet) -> None:
        """
        Called internally to generate prefetching query.

        :param queryset: Custom QuerySet to use for prefetching.
        :raises OperationalError: If field does not exist in model.
        """

        first_level_field, __, forwarded_prefetch = self.relation.partition("__")
        if first_level_field not in queryset.model._meta.fetch_fields:
            raise OperationalError(
                f"relation {first_level_field} for {queryset.model._meta.db_table} not found"
            )

        if forwarded_prefetch:
            if first_level_field not in queryset._prefetch_map:
                queryset._prefetch_map[first_level_field] = set()
            queryset._prefetch_map[first_level_field].add(
                Prefetch(forwarded_prefetch, self.queryset, to_attr=self.to_attr)
            )
        else:
            queryset._prefetch_queries.setdefault(first_level_field, []).append(
                (self.to_attr, self.queryset)
            )


def get_json_filter_operator(