MySQL redis learning and application

Relational databases such as mysql have limited read and write performance when data is stored in high concurrency situations. Nosql (non-relational database) emerged as the times require to make up for the problem. overcome the shortcomings of relational databases.

【Introduction】

## redis is a key-value storage form Nosql database is widely used. It supports master-slave replication, transaction processing, optimistic locking, complex transaction control, persistence, publishing and subscribing messages and other features.

##[Introduction to data types]

The data type of redis is simpler than that of relational database, and is divided into 5 major types: string, hashs, lists, sets, and sorted set.

1. The string type is a binary, safe data type that can store jps images or serialized pairs. Commonly used redis database commands are:

<span style="font-family:KaiTi_GB2312;">		
</span>
<span style="font-family:SimSun;">a. Set name lijie ----设置name=lijie
		b. Setnx 设置如果name存在，则返回0，设置不成功（nx--not exit）
		c. Setex 指定有效期：set haircolor 10 red   --10秒失效
		d. Setrange name 6 gmail.com  ----从第6个开始设置
		e. Mset key1 lijie1 key2 lijei2 key3 lijie3 --设置多个键值对
		f.  get --获得字符
		g. Getrange eamil 0 5  从下标为0到5的值
		h. Mget--批量返回
		i. Incr key6 --自增
		j. Incrby key5 6--以6来进行自增
		k. Decr/decrby
		l. Append key1 .net 在key1后面增加.net
		m. Strlen--返回长度</span><span style="font-family:KaiTi_GB2312;">
</span>

2. The hash type takes up less memory, commonly used commands:

		  <span style="font-family:SimSun;">a. Hset--hset user:001 name lijie
		b. Hsetnx--hsetnx user:002 name lamp
		c. Hmset---hmset user:003 name lijie age 20 sex 1
		d. Hincrby--自增
		e. Hexists--判断是否存在 hexits user:002 name
		f. Hlen----返回所有键数量
		g. Hdel--hdel user:003 age
		h. Hkeys --hkeys user:001
		i. Hvals---hvals user:003
		j. Hgetall---获取所有fileds和value</span>

3. The lists data type is divided into two data structures: linked list structure and queue. Common commands:

		<span style="font-family:SimSun;">a. Lpush--从头部压入元素：lpush list1 "hello"--栈
		b. Lrang myliist 0 -1  从头部一直去不到尾部
		c. Rpush---rpush list2 "hello"---队列
		d. Linsert---linsert list2 before hello word
		e. Lset--指定下标赋值：lset list2 1 my
		f. Lrem--从list 中删除n个和value相同的值
		g. Ipop从头弹出元素
		h. Rpop 从尾部
		i. Rpoplpush
		j. Lindex---lindex list2 2
		k. Llen---返回长度</span>

4. The sets type supports union, intersection, cross set and other operations. Use the command:

		<span style="font-family:SimSun;">a. Sadd--sadd myset1 one
		b. Smembers--查看
		c. Srem --srem myset2 "one"
		d. Spop--随机弹出
		e. Sdiff--两个集合的差集  
		f. Sdiffstor---叉集存储到指定sets里面：sdiffstore myset4 myset2 myset3
		g. Siner--返回交集/sinnerstore
		h. Sunion--并集/
		i. Smove---将第一个set中元素剪切到第二个set中 smove myset1 myset8 three
		j. Scard --查看个数
		k. Sismemeber---测试元素是不是set中元素
		l. Srandmember--随机返回元素不会删除</span>

5. Sort set is an ordered set:

		<span style="font-family:SimSun;">a. Zadd---zadd myzset “one”
		b. 取值：zrange myzet 0 -1 withscores（显示顺序）
		c. Zrem--zrem myzset two
		d. Zincrby--zincrby sset1 2 one--对顺序号进行增加
		e. Zrank--返回 索引：zrank myset3 two
		f. Zrevrank
		g. Zrerange--降序排序
		h. Zrangebyscore--按照范围返回：zrangebyscore sset2 2 4 with scores
		i. Zcount--返回数量 zcount seet2 2 4
		j. Zcard --返回 
		k. Zremrangebyrank--按照索引删除
		l. Zremrangebyscore--按照顺序删除</span>

【java application】

Redis in Java needs to introduce jar package: Import Redis.clients.jedis.jedis; # Use directly in the code: Jedis client=new Jedis("ip address",6379);, which can realize redis connection. When using the connection pool, create a connection pool class:

package com.tgb.itoo.exam.students.controller;

import java.util.ResourceBundle;

import org.springframework.util.Assert;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

public class JedisPoolTest {
	private static JedisPool jedisPool;
	
	private static JedisPoolConfig initPoolConfig(){
		 JedisPoolConfig jedisPoolConfig = new JedisPoolConfig();  
	     // 控制一个pool最多有多少个可用的的jedis实例  
//	     jedisPoolConfig.setMaxActive(1000);   
	        // 最大能够保持空闲状态的对象数  
	     jedisPoolConfig.setMaxIdle(300);  
	        // 超时时间  
	     jedisPoolConfig.setMaxWaitMillis(1000);  
	        // 在borrow一个jedis实例时，是否提前进行alidate操作；如果为true，则得到的jedis实例均是可用的；  
	     jedisPoolConfig.setTestOnBorrow(true);   
	        // 在还会给pool时，是否提前进行validate操作  
	     jedisPoolConfig.setTestOnReturn(true);  
	     return jedisPoolConfig;  
	}
	
	 /** 
     * 初始化jedis连接池 
     * <br>------------------------------<br> 
     */  
      
    public static void before() {  
        JedisPoolConfig jedisPoolConfig = initPoolConfig();    
        // 属性文件读取参数信息  
        ResourceBundle bundle = ResourceBundle.getBundle("redis_config");  
        String host = bundle.getString("redis.host");  
        int port = Integer.valueOf(bundle.getString("redis.port"));  
        int timeout = Integer.valueOf(bundle.getString("redis.timeout"));  
        String password = bundle.getString("redis.password");  
        // 构造连接池  
        jedisPool = new JedisPool(jedisPoolConfig, host, port, timeout, password);  
    }  
    

    public void testSet() {  
        Jedis jedis = null;   
        // 从池中获取一个jedis实例  
        try {  
            jedis = jedisPool.getResource();  
            jedis.set("blog_pool", "java2000_wl");  
        } catch (Exception e) {  
            // 销毁对象  
            jedisPool.returnBrokenResource(jedis);  
//            Assert.fail(e.getMessage());  
        } finally {  
            // 还会到连接池  
            jedisPool.returnResource(jedis);  
        }  
    }    
}

Pipeline Technology Application

##redis When performing continuous write operations , in order to reduce the number of times the database is opened and closed, creating a pipeline can improve performance. Actual use:

##

                Pipeline pipeline=client.pipelined();
		
		for (TemplateDetail templateDetail : templateDetails) {
			List<QuestionMain> questionMains=templateDetail.getQuestionMainList();
			for (QuestionMain questionMain : questionMains) {
				if(null!=questionMain){
				String redisKey=studenInfo.getStudentId()+"_"+studenInfo.getExamination_id()+"_"+questionMain.getId()+"_exam";
				
				try {
					pipeline.lpush(redisKey,JsonUtils.objectToJson(questionMain));
					pipeline.expire(redisKey, 7200);
				} catch (IOException e) {	
					e.printStackTrace();
				}				
				}
			}			
		}
		pipeline.sync();//管道执行

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