Django：我可以在不过滤所有模型实例的情况下检查模型实例是否与过滤器匹配

Question

我有一个模型的实例。我有一个查询集。我可以检查实例是否匹配过滤器而不过滤所有模型对象？

情况：我有一个模型Alpha，当创建这个模型时，我需要检查它是否匹配存储在模型Bravo中的用户定义的过滤器。将有许多Alpha模型和许多Bravo模型（过滤器）。

class Alpha(models.Model):
    test = models.CharField()

class Bravo(models.Model):
    test = models.CharField()

    def get_qs(self):
        # These could be longish and complex, defined by users
        return Q(test=self.test) | Q(test=f"{self.test}a")

# There will be many of these but I only want to check this instance
a = Alpha(test="testa")
# There will be many of these, I need to check if queries from get_qs match "a"
b = Bravo(test="test")

# Lots of Bravo, all need to be checked, unavoidable
for bravo in Bravo.objects.all():
    # Lots of Alpha, don't want to check them all
    # Just check "a" matches bravo.get_qs filter
    if a in Alpha.objects.filter(bravo.get_qs()):
        # Do something with "a" depending on which "b"
        pass

我的假设是

if a in Alpha.objects.filter(bravo.get_qs())

将过滤所有Alpha对象。我不想要这个，因为我不需要检查除“a”之外的任何其他实例，并且会有很多。我不想检查每个Alpha对象的所有Bravo对象。

我对其他如何做与上述类似的建议持开放态度。

Answer 1

您可以在a in Alpha.objects.filter(bravo.get_qs())中检查具有与a exists相同的主键的查询集，而不是Alpha。

alpha = Alpha.objects.filter(pk=a.pk)

for bravo in Bravo.objects.all():
    if alpha.filter(bravo.get_qs()).exists():
        # Do something with "a" depending on which "b"