[redis] Introduction to NoSQL database and redis

One 、NoSQL database

1、NoSQL The definition of
NoSQL Meaning for Not Only SQL（ not only SQL）, Non relational database in general
Different from relational databases , It does not rely on business logic to store associated data , But rather key-value Data storage in the form of key value pairs , It greatly increases the expansion ability of the database

2、NoSQL The role of database

• Use as cache , Improve access speed , Reduce IO Read operation
• Reduce CPU and IO The pressure of the , Read data directly from memory

3、NoSQL The characteristics of database

• Non compliance SQL Standards for
• I won't support it ACID
  A (Atomicity) Atomicity
  C (Consistency) Uniformity
  I (Isolation) independence
  D (Durability) persistence
• Far exceed SQL Performance of

4、 Applicable scenario

• High concurrency of data reading and writing , For example, the second kill operation of e-commerce
• Need to read and write massive amounts of data
• High scalability requirements for data

5、 Not applicable to the scene

• Need transaction support
• be based on sql Structured query storage of , Dealing with complex relationships , You need to make an ad hoc inquiry （ Ad hoc inquiry （Ad Hoc） Users according to their own needs , Flexible selection of query conditions ）

6、 common NoSQL database

• Redis
• MongoDB

Two 、redis Database introduction

1、 Concept
redis It's open source key-value The storage system
It stores value Five data formats are supported ： Include string（ character string ）、list（ Linked list ）、set（ aggregate ）、zset（sort set, Ordered set ） and hash（ Hash type ）

2、redis You can store data in memory , You can also write data to disk periodically （ Persistence ）, In addition, it also realizes master-slave（ Master-slave ） Sync

3、 install redis
Get into redis Official website ： Download address
Find the latest stable version redis, Download to local , Then upload the compressed package to Linux In the virtual machine , Then start our installation

• install C Language compiling environment , Use command
  yum install gcc
  After installation , Command view gcc edition
  gcc --version
  

• Use the unzip command to unzip the compressed package to the specified path
  
  Be careful Here's one -C This parameter , Otherwise, there may be Not found in archive This mistake
  

• Use make Command to compile
  

• Use make PREFIX=xxx( Specify the path ) install Command to install
  

• Go to the installation directory bin View under the path
  reids-benchmark： Performance testing tools
  redis-check-aof： Fix the problem aof file
  redis-check-dump： Fix the problem dump.rdb
  redis-sentinel：redis Cluster use
  redis-server：redis Server start command
  redis-cli：redis client

• Try the foreground startup redis（ Not recommended , Because after exiting redis The server will also shut down ）
  If an error is reported
  
  At this time, you have to enter the command , Build a /usr/bin/redis-server To /opt/decade/redis/bin/redis-server The soft links , You're running /usr/bin/redis-server Is running /opt/decade/redis/bin/redis-server
  ln -s /opt/decade/redis/bin/redis-server /usr/bin/redis-server
  Can start normally redis 了
  

• Try to start in the background redis
  First we will redis Extract... From the directory redis.conf Copy a copy and put it in a path , I am here /opt/decade/
  cp redis.conf /opt/decade/redis.conf
  Use vi redis.conf Modify the copied one redis.conf, adjustment daemonize Configuration item , from NO Change it to YES（ Input vi redis after , have access to / What to look for To quickly find what you are looking for ）
  daemonize Is used to specify redis Do you want to start it as a daemonic thread , thus redis It will run in the background
  
  Then we go back to redis Installation directory , Start... With the specified profile redis, You can see ,redis Running in the background
  

• Try starting the client
  Use redis-cli Command start client

• close redis
  Use it directly kill -9 redis Process number
  Input at the client shutdown
  Use redis-cli shutdown
  Use redis-cli -p redis Port number shutdown
  

If there is a mistake , Welcome to correct ！