def list(self, request, *args, **kwargs):
"""
重载 list 方法，不列出所有 tweets，必须要求指定 user_id 作为筛选条件
"""
user_id = request.query_params['user_id']
cached_tweets = TweetService.get_cached_tweet(user_id)
page = self.paginator.paginate_cached_list(cached_tweets, request)
if page is None:
# 这句查询会被翻译为
# select * from twitter_tweets
# where user_id = xxx
# order by created_at desc
# 这句 SQL 查询会用到 user 和 created_at 的联合索引
# 单纯的 user 索引是不够的
queryset = Tweet.objects.filter(
user_id=user_id).order_by('-created_at')
page = self.paginate_queryset(queryset)
serializer = TweetSerializer(
page,
context={'request': request},
many=True,
)
# 一般来说 json 格式的 response 默认都要用 hash 的格式
# 而不能用 list 的格式（约定俗成）
return self.get_paginated_response(serializer.data)
def test_create_new_tweet_before_get_cached_tweets(self):
tweet1 = self.create_tweet(self.linghu, 'tweet1')
RedisClient.clear()
conn = RedisClient.get_connection()
key = USER_TWEETS_PATTERN.format(user_id=self.linghu.id)
self.assertEqual(conn.exists(key), False)
tweet2 = self.create_tweet(self.linghu, 'tweet2')
self.assertEqual(conn.exists(key), True)
tweets = TweetService.get_cached_tweet(self.linghu.id)
self.assertEqual([t.id for t in tweets], [tweet2.id, tweet1.id])
def test_get_user_tweets(self):
tweet_ids = []
for i in range(3):
tweet = self.create_tweet(self.linghu, 'tweet {}'.format(i))
tweet_ids.append(tweet.id)
tweet_ids = tweet_ids[::-1]
RedisClient.clear()
conn = RedisClient.get_connection()
# cache miss
tweets = TweetService.get_cached_tweet(self.linghu.id)
self.assertEqual([t.id for t in tweets], tweet_ids)
# cache hit
tweets = TweetService.get_cached_tweet(self.linghu.id)
self.assertEqual([t.id for t in tweets], tweet_ids)
# cache updated
new_tweet = self.create_tweet(self.linghu, 'new tweet')
tweets = TweetService.get_cached_tweet(self.linghu.id)
tweet_ids.insert(0, new_tweet.id)
self.assertEqual([t.id for t in tweets], tweet_ids)