Redis - basic concept

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One 、NoSQL summary

1. Why NoSQL

• stand-alone MySQL The s
• Memcached（ cache ）+ MySQL + Split Vertically （ Read / write separation ）
• Sub database and sub table + Horizontal split + MySQL colony
• Now, in the latest era
  • MySQL Such relational databases are not enough , Large amount of data , Fast change
    

Why use NoSQL
User's personal information , Social networks , Location . User generated data , User logs and so on exploded .
And that's where we need to use it NoSQL database , It can handle the above situation well .

2. What is? NoSQL

NoSQL = Not Only SQL

• Non relational database in general . Traditional relational databases are difficult to deal with web2.0 Time . Especially in large-scale high concurrency communities .

3. NoSQL characteristic

• Easy to expand （ There's no relationship between the data , Good extension ）
• Large data volume and high performance （NoSQL The cache is record level , Fine grained cache , High performance ）
• Data types are diverse （ There's no need to design the database in advance , Take it and use it ）
• Traditional relational databases （RDBMS） and NoSQL

Conventional RDBMS
Structured organization ;
SQL;
Data and relationships exist in separate tables ;
Strict consistency ;
Basic business

NoSQL
It's not just data
There is no fixed query language
Key value pair storage , Column store , Document storage , Graphic database
Final consistency
CAP Theorem and BASE （ Different live ）
High performance , High availability , Highly scalable

4. NoSQL The four major categories of

• KV Key value pair
  • Redis
• Document database （bson Format ）
  • MongoDB（ Is a database based on distributed file storage , Used to process a large number of documents ）
• Column store database
  • HBase
• Graph relational database
  • What you save is not graphics , It's the relationship
  • Neo4j

Two 、Redis summary

1. What is? Redis

• Redis（Remote Dictionary Server）, Remote Dictionary Service ;
• The hottest thing right now NoSQL One of the technologies , Also known as structured database ;

2. Redis purpose

• Memory storage 、 Persistence ;
• Efficient , For caching ;
• Publish subscribe system ;
• Map information analysis ;
• timer 、 Counter （ Browse volume ）

3、 ... and 、Redis install

Official website ：https://redis.io/
（ Be careful ：Windows The needs of the system are github Upload and download , because Redis Recommended in the Linux To build ）
【 The following is about Windows Next installation steps 】

Download installation package
link ：https://pan.baidu.com/s/1h5pwR64SvjCz2_6JRNDGJw
Extraction code ：yt9h

• Unzipped installation package
  
• Open command window , Switch directory to current folder , Then enter the following command ：
  redis-server redis.windows.conf
  The default port is ：6379
  
• Do not close the previous window , Double-click to open redis-cli.exe
  
  Enter the following to test
  

Four 、Redis Basic knowledge of

• redis The default is 16 A database , By default, the first one is 0 individual ;
• redis It's single threaded , It's memory based ;
• redis The performance bottleneck is not CPU, It's the memory and network bandwidth of the machine ;
• redis Why is single thread so fast
  • High performance servers are not necessarily multi-threaded ;
  • Multithreading involves CPU Context switch ;
  • The core ：redis It puts all the data in memory , So using single thread operation is the most efficient . Multithreading will have CPU Context switching takes time . For memory , If there is no context switching, the efficiency is the highest . Read and write many times in a CPU Upper , In the case of memory , This plan is the best .

5、 ... and 、Redis Five basic data types

Redis Case insensitive commands

1. String String type

2. List List the type

• stay redis in , have access to List To express Stack 、 queue 、 Blocking queues ;
• List The command , With L The beginning represents left operation , With R The beginning represents right operation ;

3. Set Collection types

• Set All commands in are in S At the beginning ;

4. Hash Hash type

• Map aggregate ,key-map;
• This value is a Map aggregate , The nature and String There's not much difference between types , It's still a simple key-value;

5. Zset Ordered set type

• stay set On the basis of , Added a value ;
• set k1 v1 zset k1 score1 v1

6、 ... and 、Redis Three special data types

1. Geospatial Geographical location details

• Friends' positioning , The man near the , Taxi distance calculation ;
• getpos： Get the current location ： It must be a coordinate value
  
• geodist： The distance between the two
  
• georadius： Get people nearby （ Query by radius ）
  

2. Hyperloglog Base Statistics

3. Bitmap Bitmap scene operation