What are the redis data types

String（ character string ）

 

 

string yes redis Most basic types , You can understand that Memcached As like as two peas , One key Corresponding to one value.

 

string Type is binary safe . intend redis Of string Can contain any data . such as jpg Picture or serialized object .

 

string The type is Redis Basic data types ,string The maximum value of type can store 512MB.

 

Common commands ：set、get、decr、incr、mget etc. .

 

Be careful ： Maximum storage of one key 512MB.

 

Hash（ Hash ）

 

Redis hash It's a key value (key=>value) The collection ; It's a string Type of field and value Mapping table ,hash Ideal for storing objects .

 

Every hash Can be stored 232 -1 Key value pair （40 More than ）.

 

Common commands ：hget、hset、hgetall etc. .

 

Application scenarios ： Store some structured data , For example, the user's nickname 、 Age 、 Gender 、 Integral, etc. , Store a user information object data .

 

List（ list ）

 

Redis List is a simple list of strings , Sort by insertion order . You can add an element to the head of the list （ On the left ） Or tail （ On the right ）.

 

list Types are often used for message queuing services , To complete the message exchange between multiple programs .

 

Common commands ：lpush、rpush、lpop、rpop、lrange etc. .

 

List can be stored at most 232 - 1 Elements (4294967295, Each list can be stored 40 More than ).

 

Set（ aggregate ）

 

Redis Of Set yes string Unordered collection of type . Just like the list , When performing insert and delete and determining whether an element exists , Efficiency is very high . The biggest advantage of a set is that it can perform intersection, union and subtraction operations .Set The maximum number of elements that can be included is 4294967295.

Collections are implemented through hash tables , So add the , Delete , The complexity of searching is O(1).

 

Application scenarios ：

 

1、 Use intersection to find common friends .

 

2、 Using uniqueness , You can count all the independent websites you visit IP.

 

3、 Friends recommend according to tag Find the intersection , Greater than one threshold（ Of the critical value ） You can recommend .

 

Common commands ：sadd、spop、smembers、sunion etc. .

 

The maximum number of members in the collection is 232 - 1(4294967295, Each collection can store 40 More than 100 million members ).

 

zset(sorted set： Ordered set )

 

Redis zset and set The same is true. string Collection of type elements , And duplicate members are not allowed .

 

The difference is that each element is associated with a double Score of type .redis It's the scores that sort the members of a collection from small to large .

 

zset Members of are unique , But fractions (score) But it can be repeated .

 

sorted set It 's inserted in order , That is, automatic sorting .

 

Common commands ：zadd、zrange、zrem、zcard etc. .

 

When you need an ordered and non repetitive list of collections , Then you can choose sorted set data structure .

 

Application, for example, ：

 

（1） For example, store the scores of the whole class , Its collection value It can be the student number of a classmate , and score It can be achievement .

（2） Leaderboard app , List by score topN Users, etc .