姜戈 subquery/prefech_related

Question

比如我有模型：

class Location(models.Model):

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    ...

class ControlPoint(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    location = models.ForeignKey(Location, related_name='+', on_delete=models.CASCADE, verbose_name='Локация')
    order = models.IntegerField(default=0)
    route = models.ForeignKey('Route', related_name='control_points', on_delete=models.CASCADE)
    ...

class Route(models.Model):

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)

    @property
    def get_departure(self):
        return self.control_points.get(order=0)

    @property
    def get_arrival(self):
        return self.control_points.order_by('-order')[0]

    def clear_control_points(self):
        self.control_points.all().delete()


class Trip(models.Model):

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    route = models.OneToOneField(Route, related_name='trips', null=True, on_delete=models.SET_NULL)
    user = models.ForeignKey(User, related_name='trips', on_delete=models.CASCADE)
    ...

解决

根据以下cengineer的回答（非常感谢他）：

Trip.objects.filter(route_id__in=Subquery(ControlPoint.objects.filter(location_id=<location_id>).values('route_id')))

如果你知道如何以不同的方式解决这个问题，我会很高兴看到你的例子。

Answer 1

是的，您可以使用子查询解决此问题。在你的情况下应该是这样的

Trip.objects.filter(route_id__in=Subquery(ControlPoint.objects.filter(location_id=<your_location_id>).values('id')))

所以我使用了 route_id 因为当你的模型中有一个 ForeignKey 时，说 x 它被存储为 x_id 我认为这更具可读性但如果你愿意，你当然可以使用路线。

姜戈 subquery/prefech_related

Django subquery/prefech_related

django

django-queryset

django-orm