def push_newsfeed_to_cache(sender, instance, created, **kwargs):
# 只有新建时才push， update时并不push
if not created:
return
from newsfeeds.services import NewsFeedService
NewsFeedService.push_newsfeed_to_cache(instance)
def fanout_newsfeeds_batch_task(tweet_id, follower_ids):
from newsfeeds.services import NewsFeedService
newsfeeds = [
NewsFeed(user_id=follower_id, tweet_id=tweet_id)
for follower_id in follower_ids
]
NewsFeed.objects.bulk_create(newsfeeds)
for newsfeed in newsfeeds:
NewsFeedService.push_newsfeed_to_cache(newsfeed)
return "{} newsfeeds created".format(len(newsfeeds))
def fanout_newsfeeds_batch_task(tweet_id, follower_ids):
from newsfeeds.services import NewsFeedService
newsfeeds = [
NewsFeed(user_id=follower_id, tweet_id=tweet_id)
for follower_id in follower_ids
# notice here the tweet.user is the creator of tweet
]
NewsFeed.objects.bulk_create(newsfeeds)
# bulk create will not invoke post_save signal, manually push newsfeed into cache
for newsfeed in newsfeeds:
NewsFeedService.push_newsfeed_to_cache(newsfeed)
return "{} newsfeeds created".format(len(newsfeeds))
def fanout_newsfeeds_batch_task(tweet_id, follower_ids):
# import 写在里面避免循环依赖
from newsfeeds.services import NewsFeedService
# 错误的方法：将数据库操作放在 for 循环里面，效率会非常低 ->
# for follower_id in follower_ids:
# NewsFeed.objects.create(user_id=follower_id, tweet_id=tweet_id)
# 正确的方法：使用 bulk_create，会把 insert 语句合成一条 ->
newsfeeds = [
NewsFeed(user_id=follower_id, tweet_id=tweet_id)
for follower_id in follower_ids
]
NewsFeed.objects.bulk_create(newsfeeds)
# bulk create 不会触发 post_save 的 signal，所以需要手动 push 到 cache 里
for newsfeed in newsfeeds:
NewsFeedService.push_newsfeed_to_cache(newsfeed)
return "{} newsfeeds created".format(len(newsfeeds))
def fanout_newsfeeds_batch_task(tweet_id, follower_ids):
# import written inside of method to avoid reference loop.
from newsfeeds.services import NewsFeedService
# wrong way:
# can not put db operation in for loop. efficiency is super low and slow
# for follower in FriendshipService.get_followers(tweet.user):
# NewsFeed.objects.create(
# user=follower,
# tweet=tweet,
# )
# correct way: use bulk_create, then insert once
newsfeeds = [
NewsFeed(user_id=follower_id, tweet_id=tweet_id)
for follower_id in follower_ids
]
NewsFeed.objects.bulk_create(newsfeeds)
# bulk create doesn't emit post_save signal, so, need to push each newsfeed to cache manually
for newsfeed in newsfeeds:
NewsFeedService.push_newsfeed_to_cache(newsfeed)
return '{} newsfeeds created'.format(len(newsfeeds))
def push_newsfeed_to_cache(sender, instance, created, **kwargs):
# in case we save the same feed multiple times
if not created:
return
from newsfeeds.services import NewsFeedService
NewsFeedService.push_newsfeed_to_cache(instance)
