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

我有一个模型实例。我有一个查询集。我可以在不过滤所有模型对象的情况下检查实例是否匹配过滤器吗？

情况： 我有一个模型Alpha，创建此模型时我需要检查它是否与存储在模型Bravo 中的用户定义过滤器匹配。会有很多Alpha 模型和很多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，而且会有很多。我不想检查每个 Bravo 对象的所有 Alpha 对象。

我愿意接受其他关于如何做与上述类似的事情的建议。

Answer 1

您可以检查与a exists 在Alpha 中具有相同主键的查询集，而不是a in Alpha.objects.filter(bravo.get_qs())。

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"