def incr_comments_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
Tweet.objects.filter(id=instance.tweet_id).update(comments_count=F('comments_count') + 1)
RedisHelper.incr_count(instance.tweet, 'comments_count')
def incr_comments_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
# handle new comment
Tweet.objects.filter(id=instance.tweet_id)\
.update(comments_count=F('comments_count') + 1)
#invalidate_object_cache(sender=Tweet, instance=instance.tweet)
RedisHelper.incr_count(instance.tweet, 'comments_count')
def incr_likes_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
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)
RedisHelper.incr_count(instance.content_object, 'likes_count')
def incr_comment_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
# 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.incr_count(instance.tweet, 'comment_count')
print("COMMENT INCR + 1")
def decr_likes_count(sender, instance, **kwargs):
from tweets.models import Tweet
from comments.models import Comment
from django.db.models import F
model_class = instance.content_type.model_class()
if model_class == Comment:
Comment.objects.filter(id=instance.object_id).update(
likes_count=F('likes_count') + 1)
comment = instance.content_object
RedisHelper.incr_count(comment, 'likes_count')
if model_class == Tweet:
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 incr_like_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
if not created:
return
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.incr_count(instance.content_object, 'like_count')
def incr_likes_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
model_class = instance.content_type.model_class()
if model_class != Tweet:
return
# can't use tweet.likes_count += 1; tweet.save() way.
# as this is not atom action, must use update db operation.
Tweet.objects.filter(id=instance.object_id).update(likes_count=F('likes_count') + 1)
tweet = instance.content_object
RedisHelper.incr_count(tweet, 'likes_count')
def incr_likes_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
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
# 不可以使用 tweet.likes_count += 1; tweet.save() 的方式
# 因此这个操作不是原子操作，必须使用 update 语句才是原子操作
Tweet.objects.filter(id=instance.object_id).update(likes_count=F('likes_count') + 1)
tweet = instance.content_object
RedisHelper.incr_count(tweet, 'likes_count')
def incr_likes_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
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
# update db first and then call cache update
Tweet.objects.filter(id=instance.object_id).update(
likes_count=F('likes_count') + 1)
tweet = instance.content_object
RedisHelper.incr_count(tweet, 'likes_count')
def incr_likes_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
model_class = instance.content_type.model_class()
if model_class != Tweet:
return
# 不可以使用tweet = instance.content_object; tweet.likes_count += 1; tweet.save()的方式
# 因为这个操作不是原子操作，必须使用update语句才是原子操作
# SQL query: UPDATE likes_count = likes_count + 1 from tweets_table where id = <instance.object.id>
tweet = instance.content_object
Tweet.objects.filter(id=tweet.id).update(likes_count=F('likes_count') + 1)
RedisHelper.incr_count(tweet, 'likes_count')
def incr_likes_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
model_class = instance.content_type.model_class()
if model_class != Tweet:
return
# Do not use tweet.likes_count += 1; tweet_save()
# because this is not a atomic operation, we have to use update
# SQL Query: UPDATE likes_count = likes_count + 1 FROM tweets_table WHERE id=<instance.object_id>
# Method 1
Tweet.objects.filter(id=instance.object_id).update(
likes_count=F('likes_count') + 1)
RedisHelper.incr_count(instance.content_object, 'likes_count')
def incr_likes_count(sender, instance, created, **kwargs):
from tweets.models import Tweet
from django.db.models import F
if not created:
return
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
# 不可以使用 tweet.likes_count += 1; tweet.save() 的方式
# tweet = instance.content_object
# tweet.likes_count += 1
# tweet.save() -- this is wrong way!
# 因这个操作不是原子操作，必须使用 update 语句才是原子操作
# SQL Query: UPDATE likes_count = likes_count + 1 FROM tweets_table WHERE id=<instance.object_id>
# Method 1
Tweet.objects.filter(id=instance.object_id).update(likes_count=F('likes_count') + 1)
RedisHelper.incr_count(instance.content_object, 'likes_count')
def incr_likes_count(sender, instance, created, **kwargs):
from comments.models import Comment
from tweets.models import Tweet
from django.db.models import F
if not created:
return
model_class = instance.content_type.model_class()
if model_class == Comment:
# handle comment likes created
Comment.objects.filter(id=instance.object_id).update(
likes_count=F('likes_count') + 1)
comment = instance.content_object
RedisHelper.incr_count(comment, 'likes_count')
else:
# handle tweet likes created
# Don't use tweet.likes_count += 1; tweet.save()
# not atomic, must use "update"
Tweet.objects.filter(id=instance.object_id).update(
likes_count=F('likes_count') + 1)
tweet = instance.content_object
RedisHelper.incr_count(tweet, 'likes_count')