def unfollow(cls, from_user_id, to_user_id):
if from_user_id == to_user_id:
return 0
if not GateKeeper.is_switched_on('switch_friendship_to_hbase'):
# https://docs.djangoproject.com/en/3.1/ref/models/querysets/#delete
# Queryset 的 delete 操作返回两个值，一个是删了多少数据，一个是具体每种类型删了多少
# 为什么会出现多种类型数据的删除？因为可能因为 foreign key 设置了 cascade 出现级联
# 删除，也就是比如 A model 的某个属性是 B model 的 foreign key，并且设置了
# on_delete=models.CASCADE, 那么当 B 的某个数据被删除的时候，A 中的关联也会被删除。
# 所以 CASCADE 是很危险的，我们一般最好不要用，而是用 on_delete=models.SET_NULL
# 取而代之，这样至少可以避免误删除操作带来的多米诺效应。
deleted, _ = Friendship.objects.filter(
from_user_id=from_user_id,
to_user_id=to_user_id,
).delete()
return deleted
instance = cls.get_follow_instance(from_user_id, to_user_id)
if instance is None:
return 0
HBaseFollowing.delete(from_user_id=from_user_id,
created_at=instance.created_at)
HBaseFollower.delete(to_user_id=to_user_id,
created_at=instance.created_at)
return 1
def unfollow(cls, from_user_id, to_user_id):
if from_user_id == to_user_id:
return 0
# update Redis
cls.remove_following_id_in_redis(from_user_id, to_user_id)
# update DB
if not GateKeeper.is_switch_on('switch_friendship_to_hbase'):
deleted, _ = Friendship.objects.filter(
from_user_id=from_user_id,
to_user_id=to_user_id,
).delete()
return deleted
instance = cls.get_follow_instance(from_user_id, to_user_id)
if instance is None:
return 0
HBaseFollowing.delete(from_user_id=from_user_id, created_at=instance.created_at)
HBaseFollower.delete(to_user_id=to_user_id, created_at=instance.created_at)
return 1