Question

我的模型如下：我设置了Dude个，每个Dude都有一组首选项。我可以根据他们的单一偏好轻松找到Dude，但我需要找到那些喜欢两种不同的东西。我尝试将两个Q对象传递给filter()函数，但在生成的SQL中，这两个Q对象引用相同的Preference。我希望他们引用两个不同的Preferences。更糟糕的是，我需要查询相关模型的几个属性（= Preference），因此我不能使用简单的__in。

型号：

class Dude(models.Model):
    name = models.CharField(max_length=200)

class Preference(models.Model):
    name =     models.CharField(max_length=200)
    how_much = models.CharField(max_length=200)
    dude =     models.ForeignKey(Dude)

测试用例：

class DudesTestCase(TestCase):
    def setUp(self):
        dude = Dude.objects.create(name = 'Dude')
        cheese = Preference.objects.create(name = 'Cheese', how_much = "very", dude = dude)
        bacon = Preference.objects.create(name = 'Bacon', how_much = "absolutely_love", dude = dude)

    # does work
    def test_cheese_lovers(self):
        d = Dude.objects.filter(preference__name = 'Cheese', how_much = "very")
        self.assertEquals(d[0].name, 'Dude')

    # does not work - wants a single Preference to be both cheese and bacon
    def test_cheese_and_bacon_lovers(self):
        d = Dude.objects.filter(
                Q(preference__name = 'Cheese', how_much = "very"),
                Q(preference__name = 'Bacon', how_much = "absolutely_love"),
        )
        self.assertEquals(d[0].name, 'Dude')

澄清：我不想找到喜欢奶酪或培根的家伙，我需要人们同时满足这两个条件。

Answer 1

我认为这应该有用

def test_cheese_and_bacon_lovers(self):
    d = Dude.objects.filter(
        preference__name='Cheese',
        how_much__in=("very", "absolutely_love"),
    .filter(
        preference__name='Bacon',
        how_much__in=("very", "absolutely_love"),
    )
    self.assertEquals(d[0].name, 'Dude')

此用法在此处的文档中描述：
https://docs.djangoproject.com/en/1.8/topics/db/queries/#spanning-multi-valued-relationships

Answer 2

为模型添加相关名称：

class Preference(models.Model):
    name = models.CharField(max_length=200)
    dude = models.ForeignKey(Dude, related_name='preferences')

并使用IN和annotate：

Dude.objects.filter(preferences__name__in=['Cheese', 'Bacon']) \
  .annotate(cnt=Count('preferences__name') \
  .filter(cnt=2)

Django：在相关模型的多个实例上使用filter（）

2 个答案: