Take you to thoroughly understand the 16 major application scenarios of Redis!

1. Cache

String type

For example: hot data caching (such as reports, celebrities cheating), object caching, full page caching, and access data that can improve hot data.

2. Data sharing and distributed

String type, because Redis is a distributed independent service, which can be shared among multiple applications

For example: Distributed Session

<dependency> 
 <groupId>org.springframework.session</groupId> 
 <artifactId>spring-session-data-redis</artifactId> 
</dependency>

3. Distributed lock

String type setnx method, can be added successfully only if it does not exist, return true

public static boolean getLock(String key) {
    Long flag = jedis.setnx(key, "1");
    if (flag == 1) {
        jedis.expire(key, 10);
    }
    return flag == 1;
}

public static void releaseLock(String key) {
    jedis.del(key);
}

4. Global ID

int type, incrby, use atomicity

incrby userid 1000

The scene of sub-database and sub-table, take one section at a time

5. Counter

int type, incr method

For example: the number of articles read, the number of Weibo likes, a certain delay is allowed, first write to Redis and then synchronize to the database regularly

6. Current limit

int type, incr method

With the visitor's ip and other information as the key, the count will be incremented once for each visit, and false will be returned if the number of visits is exceeded.

7. Bit statistics

String type bitcount (introduction of bitmap data structure in 1.6.6)

Characters are stored in 8-bit binary

set k1 a
setbit k1 6 1
setbit k1 7 0
get k1 
/* 6 7 代表的a的二进制位的修改

a 对应的ASCII码是97，转换为二进制数据是01100001
b 对应的ASCII码是98，转换为二进制数据是01100010

因为bit非常节省空间（1 MB=8388608 bit），可以用来做大数据量的统计。
*/

For example: online user statistics, retention user statistics

setbit onlineusers 01 
setbit onlineusers 11 
setbit onlineusers 20

Support bitwise AND, bitwise OR, etc. operations

BITOPANDdestkeykey[key...] ，对一个或多个 key 求逻辑并，并将结果保存到 destkey 。       
BITOPORdestkeykey[key...] ，对一个或多个 key 求逻辑或，并将结果保存到 destkey 。 
BITOPXORdestkeykey[key...] ，对一个或多个 key 求逻辑异或，并将结果保存到 destkey 。 
BITOPNOTdestkeykey ，对给定 key 求逻辑非，并将结果保存到 destkey 。

Calculate users who are online for 7 days

BITOP "AND" "7_days_both_online_users" "day_1_online_users" "day_2_online_users" ...  "day_7_online_users"

8. Shopping cart

String or hash. All hashes that String can do can be done

key：用户id；field：商品id；value：商品数量。
+1：hincr。-1：hdecr。删除：hdel。全选：hgetall。商品数：hlen。

9. User message timeline timeline

list, doubly linked list, just as timeline directly. Insert order

10. Message queue

List provides two blocking pop operations: blpop/brpop, you can set the timeout

• blpop: blpop key1 timeout Remove and get the first element of the list. If there are no elements in the list, the list will be blocked until the waiting timeout or an element that can be popped is found.
• brpop: brpop key1 timeout Remove and get the last element of the list. If there are no elements in the list, the list will be blocked until the waiting timeout or an element that can be popped is found.

The operation above. In fact, it is the blocking queue of java. The more things you learn. The lower the cost of learning

• Queue: First-in, first-divide: rpush blpop, left head and right tail, enter the queue on the right, and leave the queue on the left
• Stack: first in, last out: rpush brpop

11. Lottery

Comes with a random value

spop myset

12. Like, sign in, punch in

If the Weibo ID above is t1001 and the user ID is u3001

Use like:t1001 to maintain all like users of this Weibo t1001

• Liked this Weibo: sadd like:t1001 u3001
• Unlike: srem like:t1001 u3001
• Like or not: sismember like:t1001 u3001
• All users who liked: smembers like:t1001
• Number of likes: scar like:t1001

Is it much simpler than the database. In addition, follow the Java PhoenixMiles public account, reply to the "back-end interview", and send you a collection of interview questions!

13. Product label

The old rule is to use tags:i5001 to maintain all the tags of the product.

• sadd tags:i5001 clear and delicate picture
• sadd tags:i5001 true color clear display
• sadd tags:i5001 The extreme process

14. Product screening

// 获取差集
sdiff set1 set2
// 获取交集（intersection ）
sinter set1 set2
// 获取并集
sunion set1 set2

If: iPhone11 is on the market

sadd brand:apple iPhone11

sadd brand:ios iPhone11

sad screensize:6.0-6.24 iPhone11

sad screentype:lcd iPhone 11

Selected products, Apple, ios, screens between 6.0-6.24, the screen material is LCD screen

sinter brand:apple brand:ios screensize:6.0-6.24 screentype:lcd

15. User attention and recommendation model

follow Follow fans

Pay attention to each other:

sadd 1:follow 2
sadd 2:fans 1
sadd 1:fans 2
sadd 2:follow 1

The people I follow also follow him (take the intersection):

sinter 1:follow 2:fans

people you may know:

用户1可能认识的人(差集)：sdiff 2:follow 1:follow
用户2可能认识的人：sdiff 1:follow 2:follow

16. Ranking

The number of news hits with id 6001 is increased by 1: zincrby hotNews:20190926 1 n6001

Get the 15 most clicked today: zrevrange hotNews:20190926 0 15 withscores

blog.csdn.net/qq_39938758/article/details/105577370