What data types does redis have and their application scenarios

One 、 data type ：

String、Hash、List、Set、zSet、HyperLogLog、Geo、Pub/Sub

　

Two 、 Application scenarios ：

1、String（ character string ）

set、setnx、get、decr、incr、mget

Cache layer （mysql Storage layer ,redis Make cache layer ）、 Counter （ For example, the number of videos played , Blog views, etc ）、 share session、 How many seconds can the SMS verification code be obtained again

2、Hash（hashMap）

hset、hget、hdel、hlen、hexists、hkeys、hvals、hgetall

Store user information

3、List（ Double linked list ）

lpush、rpush、lpop、rpop、brpop、lrange、lindex、len、lrem

Attention list 、 Fans list

Message queue ：

lpush + lpop = Stack

lpush + rpop = queue

lpush + ltrim = Collection co., LTD.

lpush + brpop = Message queue

It can also be used list Of lrange Realize simple paging query

4、Set

sadd、spop、sismember、srem、sunion、sdiff

Set elements do not repeat , Support addition, deletion, modification and query in the collection 、 intersect 、 Combine 、 Difference set 、 Collection

（1） label

User interest tags tag, Other preferences of people with the same tag can be obtained according to the tag , For example, novel recommendations when reading novels , And video recommendations when watching videos

（2） Generate random number （ Luck draw ）

（3） Social needs

5、SortedSet

zadd、zcard、zscore、zrank、zrem、zincrby、zrange

Set elements do not repeat , And it can be sorted , according to csore Sort

（1） The list

Video playback list 、 Likes list, etc

notes ：redis key The design of the

Use colons for segmented storage , The hierarchy is clear , It is conducive to data analysis on the client

6、HyperLogLog

pfadd、pfcount

HyperLogLog Fixed occupied space ,12k about , It can be estimated that about 2^64 The cardinal number of elements

Count the user visits of a page

Although it can also be used set do , But there are tens of millions of data , It will be a very big expense

7、geo

Geoadd： Add coordinates of a geographic location

Geopos： Get the coordinates of a geographical location

Geodist： Gets the distance between two geographical locations

GEORADIUS： Gets the set of geographical locations within a specified range based on the given geographical location coordinates

GEOHASH： To obtain a geographic location geohash value

For example, meituan takeout shows how far away the business is from you , The longitude and latitude coordinates of merchants can be stored in the database , adopt redis Of geo Calculate the distance

8、Pub/Sub

Publish subscribe , There are few practical application scenarios , but redis The sentinel mechanism of , In fact, one of them is useful Pub/Sub.