django - prefetch_related() 的无效参数

Question

我正在尝试使用 PersonScore 对这 3 个表进行内部联接，但找不到 persontype。我究竟做错了什么？

楷模:

class PersonScore(models.Model):
    id = models.IntegerField(primary_key=True)  # AutoField?
    person = models.ForeignKey(‘Person’)

class Person(models.Model):
    id = models.IntegerField(primary_key=True)  # AutoField?
    name = models.CharField(max_length=255)

class PersonType(models.Model):
    person = models.ForeignKey(‘Person’)
    type = models.CharField(max_length=255)

代码:

PersonScore.objects.filter(person__name="Bob").prefetch_related("person__persontype")

错误:

Cannot find 'persontype' on Person object, 'person__persontype' is an invalid parameter to prefetch_related()

代码:

PersonScore.objects.filter(person__name="Bob").prefetch_related("person__persontype_set")

错误:

KeyError: (1L,)

Answer 1

在 PersonScore 中，您应该使用 select_related 而不是 prefetch_related

    PersonScore.objects.filter(person__name="Bob").select_related("person__persontype")

如果你想使用 prefetch_related，你将使用它与 Person

    Person.objects.filter(personscore_set__name="Bob").prefetch_related("personscore_set"

您可以在此处查看更多详细信息: What's the difference between select_related and prefetch_related in Django ORM?

我希望这对你有帮助。