Introduction to Redis

• Redis is a key-value-oriented memory database for data types, which can meet our needs for fast reading and writing of massive data.
• Is a nosql non-relational database
• Redis keys can only be string-type values that can be of many data types
  • String string
  • Hash hash
  • List string list
  • Set string set
  • sorted set ordered string set
• Characteristics of Redis
  • High Performance: Reading 11w/s and writing 8.1w/s is a single-threaded service
  • Atomicity: Ensuring Data Accuracy
  • Persistent storage: (RDB snapshots, AOF logs)
  • Master-slave structure
  • After Cluster Support 3.0
• Application scenarios
  • Take Sina Weibo as an example
  • hash Focus List, Fan List, etc.
  • Number of String Weibo Fans
  • sorted set popular microblogs, TopN
• Note: Redis is written in c language. Before installing Redis, we need to configure the compilation environment of c language.
• Basic instructions of Redis
  • keys?* []? Wait to see if key is disabled in a regular production environment
  • exists key determines whether a key exists
  • del key1 key2... Delete key-value pairs
  • help View help
  • Qut / exit exit exit exit client
  • Note: Redis commands are case-insensitive
• Characteristics of Redis database
  • Multi-database
    • Each database is named after an incremental number starting at 0. Customization is not supported.
    • Redis supports 16 databases by default, and you can modify the default by modifying the database parameter
    • Redis defaults to database 0
    • Select digits can select databases
    • Multiple databases are not completely isolated
    • flushall: Clear all data under the Redis instance
      • flushdb empties all data in the current database

Redis Common Data Types

String

• String type is the most basic data type of Redis. It can store any form of data, including binary data and so on. The maximum storage capacity of a string-type value is 1GB

• Add data

  • set k v

  • 127.0.0.1:6379> set k1 v1
    OK
    

  • Add more than one data at a time

  • mset k2 v2 k3 v3

  • 127.0.0.1:6379> mset k2 v2 k3 v3
    OK
    

• get data

  • get k1

  • 127.0.0.1:6379> get k1
    "v1"
    

  • mget k2 k3

  • 127.0.0.1:6379> mget k2 k3
    1) "v2"
    2) "v3"
    

• Increasing and Decreasing

  • incr Incremental Decrease

  • 127.0.0.1:6379> set num 1
    OK
    127.0.0.1:6379> incr num
    (integer) 2
    127.0.0.1:6379> decr num
    (integer) 1
    

• Increase and decrease according to specified type

  • incrby Incremental Decrease by Decrease

  • 127.0.0.1:6379> incrby num 2
    (integer) 3
    127.0.0.1:6379> decrby num 2
    (integer) 1
    

  • Floating-point self-increasing can not be reduced by floating-point self-increasing

  • 127.0.0.1:6379> incrbyfloat num 1.1
    "2.1"
    127.0.0.1:6379> decrbyfloat num 1.1
    (error) ERR unknown command 'decrbyfloat'
    

• Get Length

  • 127.0.0.1:6379> set k asdsad
    OK
    127.0.0.1:6379> get k
    "asdsad"
    127.0.0.1:6379> strlen k
    (integer) 6
    

hash

• The value of hash type stores the mapping of field and field value. The field and field value can only be a string, and other data types are not supported. The number of hash keys can store 2 ^ 32-1 fields

• Add data

  • 127.0.0.1:6379> hset user name zs
    (integer) 1
    127.0.0.1:6379> hmset users name ls age 18
    OK
    

• get data

  • 127.0.0.1:6379> hget user name       Get the specified k Value
    "zs"
    127.0.0.1:6379> hmget users name age   Get the specified k Multiple values
    1) "ls"
    2) "18"
    127.0.0.1:6379> hlen users     Obtain k Quantity
    (integer) 2
    127.0.0.1:6379> hkeys users    Get all k
    1) "name"
    2) "age"
    127.0.0.1:6379> hvals users     Get all v
    1) "ls"
    2) "18"
    127.0.0.1:6379> hgetall users    Get all kv Yes
    1) "name"
    2) "ls"
    3) "age"
    4) "18"
    

• Judging whether a key exists in a hash

  • 127.0.0.1:6379> hexists user name
    (integer) 1
    127.0.0.1:6379> hexists user age
    (integer) 0
    

• Increase progressively

  • Hincrby hash type does not have hincr command

• Delete data

  • hdel

List

• Is an ordered list of string types. The internal implementation of the list is implemented using a two-way linked list.
  • Lists can also be used as queues, such as first in first out queues
  • A list-type key can hold up to 32-1 elements of 2.
• Common instructions
  • lpush/rpush/lpop/rpop Add data from left/right and extract data from left/right
  • llen/lrange Gets the length of the list, Gets the value of the specified range of the list, Views all 0-1
  • lindex queries data at specified corner locations
  • lset Modifies the Value of the Specified Corner

set

• All elements in a set set set are unreplicated and disordered
  • Keys of a collection type store up to 32-1 elements of 2
• Common commands
  • sadd/smembers/srem/sismember
    • Adding elements to a collection to get the number of collection summary elements deleting elements with specified values in the collection does not exist, that is, deleting failed return value of 0 and successfully returning value of 1 to see if a specified value exists
  • sdiff difference set
  • sinter intersection
  • sunion union returns the result directly
  • sdiffstore/sinterstore/sunionstore results exist in another specified collection
  • scard gets the length of the collection

sorted set

• Ordered sets associate a score for each element on the basis of the set, and according to the score, the elements with the highest score can be obtained by sorting.
• Common instructions
  • zadd adds the value of the specified score to the specified key
  • zscore to see the score of the specified value
  • The first few scores obtained by zrange are small to large
  • zrevrange gets the first few points in reverse order to be small
  • zrangebyscore gets the specified element according to the score. By default, the closed interval can be used to use "(" to use the open interval.
  • Zicrby Specified Element Score Self-Increasing
  • zcard gets the number of elements in a set
  • zcount gets the elements within the specified score range
  • zrem deletes specified elements in a collection

Java Operation Redis

• Simple single-machine connection

  • package jredistest.jredisa;
    
    import redis.clients.jedis.Jedis;
    /**
     * Simple single-machine connection
     * @author zhao
     *
     */
    public class RedisDemo01 {
    	public static void main(String[] args) {
    		Jedis jedis = new Jedis("192.168.32.110",6379);
    		
    		jedis.set("aaa", "111");
    		
    		String value =jedis.get("str1");
    		
    		System.out.println(value);
    		
    		jedis.close();	
    	}
    
    }
    
    

• Connection pool connection

  • package jredistest.jredisa;
    
    import redis.clients.jedis.Jedis;
    import redis.clients.jedis.JedisPool;
    import redis.clients.jedis.JedisPoolConfig;
    
    
    /**
     * Single-machine connection pool
     * 
     * @author zhao
     *
     */
    public class jredisDeml {
    	public static void main(String[] args) {
    		//Configuration information of connection pool
    				JedisPoolConfig poolConfig = new JedisPoolConfig();
    				//Maximum number of idle connections in connection pool
    				poolConfig.setMaxIdle(10);
    				//Maximum number of connections allowed to be created in connection pool
    				poolConfig.setMaxTotal(100);
    				//Maximum waiting time for creating links
    				poolConfig.setMaxWaitMillis(2000);
    				//Represents that links are tested when they are removed from the connection pool to ensure that the extracted links are available.
    				poolConfig.setTestOnBorrow(true);
    				
    				//Get the connection pool
    				JedisPool jedisPool = new JedisPool(poolConfig, "192.168.32.110", 6379);
    				//Get a jedis link from the connection pool
    				Jedis jedis = jedisPool.getResource();
    				String value = jedis.get("str");
    				System.out.println(value);
    				//Return links to connection pools
    				jedis.close();
    				
    				//Close connection pool
    				jedisPool.close();
    				
    	}
    
    }
    
    package jredistest.jredisa;
    
    import redis.clients.jedis.Jedis;
    import redis.clients.jedis.JedisPool;
    import redis.clients.jedis.JedisPoolConfig;
    
    public class jidisTest1 {
    	private jidisTest1(){}
    	private static JedisPool jedisPool=null;
    	
    	/**
    	 * Getting connections from connection pools
    	 * @return
    	 */
    	public static synchronized Jedis getJedis() {
    		if(jedisPool==null) {			
    			JedisPoolConfig jedisPoolConfig = new JedisPoolConfig();
    			//Specifies the maximum number of empty connections in the connection pool
    			jedisPoolConfig.setMaxIdle(10);
    			//Specifies the maximum number of connections in the connection pool
    			jedisPoolConfig.setMaxTotal(100);
    			//Setting Maximum Connection Timeout
    			jedisPoolConfig.setMaxWaitMillis(2000);
    			
    			jedisPoolConfig.setTestOnBorrow(true);
    			
    			jedisPool = new JedisPool(jedisPoolConfig,"192.168.32.110",6379);
    			
    		}
    		return jedisPool.getResource();
    	}
    	/**
    	 * Return connection pool connection
    	 * @param jedis
    	 */
    	public static void returnResource(Jedis jedis) {
    		jedis.close();
    	}
    	/**
    	 * Close connection pool
    	 */
    	public static void closePool() {
    		jedisPool.close();
    	}
    	
    	
    
    }