django - 同一行的插入正在发生，如果 iti 已经存在于 DB Django-rest-framework，PostgreSQL 中，如何拒绝插入

Question

我正在尝试为社交应用创建后端。在数据库中插入 friend 关系的同时，也插入了数据库中已经存在的关系。

例子:用户 1 和用户 2 已经是好友所以，数据库中的行:1,2,3，日期现在数据库不应该再接受同一行，但它正在接受!!!如何拒绝或限制同一行的多次插入。

我的看法:

class Friendship(viewsets.ModelViewSet):
    """Handles Creating Friendship"""
    authentication_classes = (TokenAuthentication,)
    serializer_class = UserFriendSerializer
    permission_classes = (permissions.FriendCreate,IsAuthenticated)
    queryset = Friends.objects.all()


    def perform_create(self, serializer):
        """Sets the friendship status to user"""

        serializer.save(username = self.request.user)

我的序列化器:

class UserFriendSerializer(serializers.ModelSerializer):
    """A serializer for adding and removing Friends"""

    class Meta:
        model = Friends
        fields = ('user_id_1','user_id_2','status',)

    def create(self, validated_data):
        """Create user friendship with lesser id in first column"""

        friend_1 = validated_data['user_id_1']
        friend_2 = validated_data['user_id_2']

        if friend_1.pk > friend_2.pk:
            temp = friend_1
            friend_1 = friend_2
            friend_2 = temp

        friend = Friends(
            user_id_1 = friend_1,
            user_id_2 = friend_2,
            status = validated_data['status'],
        )

        friend.save()

        return friend

我的模型:

class Friends(models.Model):
    '''Friend's or Relationship between user's and their relation status'''
    user_id_1 = models.ForeignKey(User,on_delete=models.CASCADE,related_name='user_a')
    user_id_2 = models.ForeignKey(User,on_delete=models.CASCADE,related_name='user_b')
    status    = models.PositiveSmallIntegerField()
    friends_on = models.DateTimeField(auto_now_add=True,auto_now=False)

    def __str__(self):
        """Returns model as a String"""
        return str(self.user_id_1)

    class Meta:
        verbose_name_plural = "Friends"

Answer 1

如果我理解你是对的，你需要 unique-together

class Friends(models.Model):
    """Friend's or Relationship between user's and their relation status"""
    user_id_1 = models.ForeignKey(User,on_delete=models.CASCADE,related_name='user_a')
    user_id_2 = models.ForeignKey(User,on_delete=models.CASCADE,related_name='user_b')
    status    = models.PositiveSmallIntegerField()
    friends_on = models.DateTimeField(auto_now_add=True,auto_now=False)

    def __str__(self):
        """Returns model as a String"""
        return str(self.user_id_1)

    class Meta:
        verbose_name_plural = "Friends"
        unique_together = ("user_id_1", "user_id_2")