Hello everyone , I'm cabbage . This article mainly explains Redis A brief introduction to the five common data types of database and their data storage space , If you get something after reading the article , You can support bloggers three times in a row ~, Hee hee .

One 、 What is? Redis？

• REmote DIctionary Server(Redis) It's a key-value The storage system . It is often referred to as a data structure server , Because of the value （value） It can be character string (String), Hash (Map), list (list), aggregate (sets) and Ordered set (sorted sets) Other types .
• The data types to be introduced in this article , Is for value （value） Of , instead of key.

Two 、 Client connection Redis

• All the operations in this article are in Linux Under the system
• Use Redis Client operation Redis database , First of all, turn on Redis The service side , Then use the following command line to connect Redis The server ：

[[email protected] redis-6.2.6]# cd /usr/local/bin/
[[email protected] bin]# redis-cli -a 123456
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> ping
PONG

3、 ... and 、Redis Data storage format

• redis Itself is a Map, All of the data are based on key-value Form storage of
• Data type refers to the type of data stored , That is to say value The type of part ,key Parts are always strings
  

Four 、 character string (String)

• Redis The related commands of string data type are used for management redis A string value
• Stored data ： Single data , The simplest type of data storage , It is also the most commonly used data storage type
• The format of data storage ： One storage space holds one data
• Store content ： You usually use strings , If the string is presented as an integer , It can be used as a digital operation
  

The figure below lists redis Common commands for strings ：

Be careful ： These instructions must be typed by yourself , Practice makes perfect . For instruction operations that will not , You can see the official documents .

5、 ... and 、 Hash (hash)

• For the string type mentioned above , If you store object class data , The operation with frequent update requirements will be very troublesome , So you have a hash data structure .
• New storage requirements ： Grouping a series of stored data , Easy to manage , Typical applications store object information .
• The required storage structure ： One storage space holds multiple key value pairs .
• hash type ： The bottom layer uses hash table structure to realize data storage .

hash Precautions for type data operation ：

• hash Type value Only strings can be stored , Storage of other data types is not allowed , There is no nesting . If the data is not available , The corresponding value is （nil）
• Every hash Can be stored 2³² - 1 Key value pairs
• hash The type is very close to the data storage form of the object , And you can add and delete object attributes flexibly . but hash It's not designed to store a lot of objects , Remember not to abuse , Not to mention hash Use as an object list
• hgetall Operation can get all properties , If inside field Too much , The efficiency of traversing the whole data is very low , It may become the bottleneck of data access

The figure below lists redis Common instructions for hashing ：

6、 ... and 、 list (list)

• Data storage requirements ： Store multiple data , And the order of data into the storage space is distinguished .
• The required storage structure ： One storage space holds multiple data , And through the data can reflect the order of entry .
• list type ： Save multiple data , The bottom layer uses bidirectional linked list storage structure .

list Type data operation considerations ：

• list The data stored in is string Type of , The total data capacity is limited , most 2³²-1 individual .
• list With the concept of indexing , But when operating data, it is usually done in the form of queue , Or in the form of stack stack stack operation .
• Get all data operation end index set to -1
• list Data can be paged , Usually the information on the first page comes from list, The second page and more information is loaded in the form of a database .

The figure below lists redis Common instructions for lists ：

7、 ... and 、 aggregate (Set)

• New storage requirements ： Store a lot of data , Provide more efficiency in queries .
• The required storage structure ： Can hold a lot of data , Efficient internal storage mechanism , Easy to query .
• set type ： And hash The storage structure is exactly the same , Just store the key , Are not stored value (nil), And the value is not allowed to repeat .

set Precautions for type data operation ：

• set Type does not allow duplicate data , If the added data is in set There is already , Only one copy will be kept .
• set Although with hash The storage structure of is the same , But it can't be enabled hash Space to store values in .

The figure below lists redis aggregate set Common instructions for ：

8、 ... and 、 Ordered set (sorted set)

• New storage requirements ： Data sorting is conducive to the effective display of data , Need to provide a way to sort according to their own characteristics .
• The required storage structure ： New storage model , You can save sortable data .
• sorted_set type ： stay set Add sortable fields based on the storage structure of .

sorted_set Precautions for type data operation ：

• score The integer range of the saved data is ：-9007199254740992~9007199254740992
• score The stored data can also be a double precision double value , Characteristics based on double precision floating point numbers , Accuracy may be lost , Be careful when using
• sorted_set The underlying storage is still based on set Structural , So the data can't be duplicated , If you add the same data repeatedly ,score Values will be repeatedly overridden , Keep the result of the last modification

The figure below lists redis Common instructions for ordered sets ：

Thank you for reading , Progress together , Hee hee ~