Redis uses LIST to cache the latest comments

implemented

Assuming product a, there are currently five reviews 1, 2, 3, 4, and 5.Synchronized from database to redis, here we require the latest comment to be placed at the top of the queue.

lpush a_comments 1lpush a_comments 2lpush a_comments 3lpush a_comments 4lpush a_comments 5

At this time, the user has a new comment 6 on a, which is entered into the database first, and then into redis

lpush a_comments 6

Inquiry, here are 2 items as one page, first count the number of items

llen a_comments

Get 6 pieces of data, the number of pages 6/2 = 3
The latest comment pagination data

# first page 6,5lrange a_comments 0 1# Second page 4,3lrange a_comments 2 3# 3rd page 2,1 lrange a_comments 4 5

Defects

It doesn't seem like there is a problem with the above, assuming you are looking at the first page of comments now, you see 6,5.At this time, a new comment 7 is generated and added to the head of the team.At this point you are looking at the second page, it is not 4,3.Instead 5, 4.You have clearly read these 5 on the first page.