def decr_comments_count(sender, instance, **kwargs):
from tweets.models import Tweet
from django.db.models import F
# handle comment deletion
Tweet.objects.filter(id=instance.tweet_id) \
.update(comments_count=F('comments_count') - 1)
RedisHelper.decr_count(instance.tweet, 'comments_count')
def decr_comments_count(sender, instance, **kwargs):
from tweets.models import Tweet
from django.db.models import F
Tweet.objects.filter(id=instance.tweet_id)\
.update(comments_count=F('comments_count') - 1)
invalidate_object_cache(sender=Tweet, instance=instance.tweet)
RedisHelper.decr_count(instance.tweet, 'comments_count')
def decr_comment_count(sender, instance, **kwargs):
from tweets.models import Tweet
from django.db.models import F
# atomic operations for concurrency safe
# django F translated SQL ensures concurrency safe in db level
Tweet.objects.filter(id=instance.tweet_id) \
.update(comment_count=F('comment_count') - 1)
# extra counter in cache
# the cached popular object should not be invalid frequently
RedisHelper.decr_count(instance.tweet, 'comment_count')
def decr_likes_count(sender, instance, **kwargs):
from tweets.models import Tweet
from django.db.models import F
model_class = instance.content_type.model_class()
if model_class != Tweet:
return
Tweet.objects.filter(id=instance.object_id).update(likes_count = F('likes_count') - 1)
tweet = instance.content_object
RedisHelper.decr_count(tweet, 'likes_count')
def decr_likes_count(sender, instance, **kwargs):
from tweets.models import Tweet
from django.db.models import F
model_class = instance.content_type.model_class()
if model_class != Tweet:
# TODO HOMEWORK 给 Comment 使用类似的方法进行 likes_count 的统计
return
# handle tweet likes cancel
Tweet.objects.filter(id=instance.object_id).update(likes_count=F('likes_count') - 1)
RedisHelper.decr_count(instance.content_object, 'likes_count')
def decr_likes_count(sender, instance, **kwargs):
from tweets.models import Tweet
from django.db.models import F
model_class = instance.content_type.model_class()
if model_class != Tweet:
# TODO: we can later do similar things to calculate number of likes for comments
return
Tweet.objects.filter(id=instance.object_id).update(
likes_count=F('likes_count') - 1)
tweet = instance.content_object
RedisHelper.decr_count(tweet, 'likes_count')
def decr_like_count(sender, instance, **kwargs):
from tweets.models import Tweet
model_class = instance.content_type.model_class()
if model_class != Tweet:
return
# atomic operations for concurrency safe
# django F translated SQL ensures concurrency safe in db level
Tweet.objects.filter(id=instance.object_id)\
.update(like_count=F('like_count') - 1)
# extra counter in cache
# the cached popular object should not be invalid frequently
RedisHelper.decr_count(instance.content_object, 'like_count')
def decr_likes_count(sender, instance, **kwargs):
from comments.models import Comment
from tweets.models import Tweet
from django.db.models import F
model_class = instance.content_type.model_class()
if model_class == Comment:
# handle comment likes canceled
Comment.objects.filter(id=instance.object_id).update(
likes_count=F('likes_count') - 1)
comment = instance.content_object
RedisHelper.decr_count(comment, 'likes_count')
else:
# handle tweet likes canceled
Tweet.objects.filter(id=instance.object_id).update(
likes_count=F('likes_count') - 1)
tweet = instance.content_object
RedisHelper.decr_count(tweet, 'likes_count')