django

Question

我在django中有两个模型，定义如下。 CreativeStatus模型：

class RtbdCreativeStatus(models.Model):
    creative_id = models.CharField(max_length=500, primary_key=True)
    advertiser_id = models.CharField(max_length=100, primary_key=True)
    exposure_level = models.CharField(max_length=125)
    modified_on = models.DateTimeField()
    modified_by = models.CharField(max_length=100)


class RtbdCreative(models.Model):
    id = models.AutoField(primary_key=True)
    advertiser_id = models.ForeignKey(RtbdCreativeStatus, on_delete=models.CASCADE)
    creative_id = models.ForeignKey(RtbdCreativeStatus, on_delete=models.CASCADE)
    country_id = models.IntegerField()
    adm = models.CharField(max_length=255, null=True, blank=True)
    sample_url = models.CharField(max_length=500)
    landing_page = models.CharField(max_length=500, null=True, blank=True)
    html = models.CharField(max_length=500)
    creative_attributes = models.CommaSeparatedIntegerField(max_length=150, null=True, blank=True)
    advertiser_domains = models.CharField(max_length=500)
    description = models.CharField(max_length=500, null=True, blank=True)
    created_on = models.DateTimeField(auto_now=True, auto_now_add=True)
    creative_type = models.CharField(max_length=50, null=True, blank=True)
    demand_source_type_id = models.IntegerField()
    revalidate = models.BooleanField(default=False)

（creative_id，advertiser_id）组合在我的CreativeStatus表中是唯一的。我希望这个组合成为Creative表的外键。我尝试添加它但我收到此错误。

1）如何使用两个组合键作为我的外键来实现此连接。

2）我的查询应该是从CreativeStatus表中获取其状态的所有广告素材。

更新1

在阅读下面的答案时，我更新了我的模型，如下所述：

class RtbdCreative(models.Model):
    id = models.AutoField(primary_key=True)
    advertiser_id = models.ForeignKey(RtbdCreativeStatus, to_field='advertiser_id', related_name='advertiser', db_column='advertiser_id', on_delete=models.CASCADE)
    creative_id = models.ForeignKey(RtbdCreativeStatus, to_field='creative_id', related_name='creative', db_column='creative_id', on_delete=models.CASCADE)
    country_id = models.IntegerField()
    adm = models.CharField(max_length=255, null=True, blank=True)
    sample_url = models.CharField(max_length=500)
    landing_page = models.CharField(max_length=500, null=True, blank=True)
    html = models.CharField(max_length=500)
    creative_attributes = models.CommaSeparatedIntegerField(max_length=150, null=True, blank=True)
    advertiser_domains = models.CharField(max_length=500)
    description = models.CharField(max_length=500, null=True, blank=True)
    created_on = models.DateTimeField(auto_now=True, auto_now_add=True)
    creative_type = models.CharField(max_length=50, null=True, blank=True)
    demand_source_type_id = models.IntegerField()
    revalidate = models.BooleanField(default=False)

现在我收到此错误。我将advertiser_id，craetive_id组合为唯一。但是django希望两者都是独一无二的。我能做些什么让它发挥作用？

Answer 1

如ERRROS中所述，当您要为同一个Model添加多个外键时，需要添加related_name作为参数。

class Creative(models.Model):
    id = models.AutoField(primary_key=True)
    advertiser_id = models.ForeignKey(RtbdCreativeStatus,
                                      related_name="Advertiser", on_delete=models.CASCADE)
    creative_id = models.ForeignKey(RtbdCreativeStatus,
                                    related_name="Creative",
                                    on_delete=models.CASCADE)
    country_id = models.IntegerField()
    adm = models.CharField(max_length=255, null=True, blank=True)
    sample_url = models.CharField(max_length=500)
    landing_page = models.CharField(max_length=500, null=True, blank=True)
    html = models.CharField(max_length=500)
    creative_attributes = models.CommaSeparatedIntegerField(
        max_length=150, null=True, blank=True)
    advertiser_domains = models.CharField(max_length=500)
    description = models.CharField(max_length=500, null=True, blank=True)
    created_on = models.DateTimeField(auto_now=True, auto_now_add=True)
    creative_type = models.CharField(max_length=50, null=True, blank=True)
    demand_source_type_id = models.IntegerField()
    revalidate = models.BooleanField(default=False)

Answer 2

当您向同一个表添加多个ForeignKeys时，您应该覆盖字段的related_name选项，以便可以轻松区分字段。

您可以实施自定义验证，以检查creative_id和advertiser_id的唯一性，

class Creative(models.Model):
    advertiser_id = models.ForeignKey(CreativeStatus,
                                  related_name="advertisers")
    creative_id = models.ForeignKey(CreativeStatus,
                                related_name="creatives")

    def clean(self):
        data = self.cleaned_data
        if not data['advertiser_id'] == data['creative_id']:
            raise ValidationError("Unique Constraint failed {}, {}".format(self.advertiser_id, self.creative_id))
        return data

您可以使用相关名称从CreativeStatus查询您的广告素材。

creative_status_obj = CreativeStatus.objects.get(pk=some_pk)#or any query.
#All creatives of the given object can be queried using reverse relation.
creatives = creative_status_obj.creatives.all()

Answer 3

我刚刚看到 models.ForeignObject （ models.ForeignKey 的超类）的参数为to_fields。在这种情况下，可以使用它为复合主键或唯一键定义外键。

    advertiser_creative_id = models.ForeignObject(RtbdCreativeStatus, to_fields=['advertiser_id', 'creative_id'], related_name='abc', on_delete=models.CASCADE)

也有一个from_fields参数。它可用于用to_fields映射字段。 请参阅https://docs.djangoproject.com/en/2.2/_modules/django/db/models/fields/related/