preface

Today, I will share five data structures of Redis and their use scenarios in actual combat

1, Redis data structure?

We all know that redis is an indispensable middleware tool in large-scale systems. It can support high concurrency scenarios or distributed locks. This is inseparable from his design architecture and underlying data structure. Redis is a non relational database with K and V structure. There are five data types. They are string, hash, list, set and zset. The data types we mentioned are only different from values, and key s are of string type. Here I drew a picture.

2, string common methods and usage scenarios

1. Introduction to common methods

#String common operations
set key value						//Store key value pairs of strings
mset key value [key value  ...]		//Batch store key value pairs of strings
setnx key value						//Stores a key value pair of a nonexistent string
get key								//Get a value according to the key
mget key [key  ...]					//Get value in batch
del key [key ...]						//Delete key
expire key seconds					//Set the expiration time of a key

#Atomic addition and subtraction
incr key					//Add 1 to the numeric value stored in the key
decr key					//J subtract 1 from the digital value stored in the key
incrby key increment		//Add increment to the value stored in the key
decrby key decrement		//decrement the value stored in the key

Briefly demonstrate:

2. Introduction to string usage scenario

• Ordinary single value cache (generally stores the user's token)
  set key value
  get key

• Object cache (storing user information)
  set user:110:info value(json data format)
  mset user:110:name fafa user:110:age 18
  
• Distributed lock
  setnx product:10010 true
  del product:10010
  set product:10010 true ex 10 nx
  
  
  Set the maximum duration of locking to 60s. If the business logic processing has not been completed within 60s, the lock will be released. Of course, in the actual production process, we have many means to prevent the lock from being released before the business logic is processed (the lock continues its life, and reisson has been implemented). Our command is mainly to prevent the deadlock caused by the accidental termination of the program.
• Counter
  incr
  
  For example, the number of people viewing my csdn blog posts. Check the following number once and add 1. The data structure can be designed like this. incr wenzhang:10
  
• Global serial number of distributed system
  incrby pid 10000 / / batch generation of serial numbers can improve performance
  

3, Common hash methods and usage scenarios

1. Common hash methods

HSET key field value 			//Store the key value of a hash table key
HSETNX key field value			//Store the key value of a non-existent hash table key
HMSET key field value [field value ...] 	//Store multiple key value pairs in a hash table key
HGET key field 					//Get the field key value corresponding to the hash table key
HMGET key field [field ...] 	//Batch obtain multiple field key values in hash table key
HDEL key field [field ...] 		//Delete the field key value in the hash table key
HLEN key						//Returns the number of field s in the hash table key
HGETALL key						//Returns all key values in the hash table key

HINCRBY  key  field  increment 	//Add increment to the value of the field key in the hash table key

2.hash usage scenario

• Object cache (if multiple fields of the cache object are frequently modified, the hash structure has higher performance than the string structure)
  hmset user {userId}:name fafa {userId}:age 18
  
• Shopping cart scene
  1. The user id is key
  2. The commodity id is field
  3 commodity quantity value
  Shopping cart operation:
  Add item: hset cart:20 10010 1
  Added quantity: hincrby Cart: 20 10010
  Total number of goods: Helen Cart: 20
  Deleted item: hdel cart:20 10013
  Get all items in the shopping cart: hgetall cart:20
  
  Command operation:
  

4, list common methods and usage scenarios

1. Common methods

List Common operation
LPUSH key value [value ...] 	//Insert one or more values value into the header (leftmost) of the key list
RPUSH key value [value ...]	 	//Insert one or more values value at the end of the key list (rightmost)
LPOP key						//Removes and returns the header element of the key list
RPOP key						//Removes and returns the last element of the key list
LRANGE key start stop			//Returns the elements within the specified interval in the list key. The interval is specified by offset start and stop

BLPOP key [key ...] timeout		//Pop up an element from the header of the key list. If there is no element in the list, block and wait 					 Timeout seconds. If timeout=0, it will block and wait all the time
BRPOP key [key ...] timeout 	//Pop up an element from the end of the key list. If there is no element in the list, block and wait 					 Timeout seconds. If timeout=0, it will block and wait all the time

2.list usage scenario

• Common data structures
  Stack: lpush + lpop or rpush + rpop
  Queue: lpush + rpop or rpush + lpop
  Blocking MQ (blocking queue): lpush +brpop or rpush + blpop
  Stack:
  
  Queue:
  
  Blocking queue:
  
• Micro-blog and WeChat official account message flow
  Let's look at a picture first
  
  Wechat subscription number, I believe everyone should be familiar with it! Here I subscribe to the programmer column and the java technology Jianghu. As long as I subscribe to people, they add their article id to my list every time they post an article. In this way, they can get it from this list every time they enter my wechat. This is the use scenario of list. For example:
  The programmer column has posted an article with id 111
  lpush msg:{tuofafaId} 111
  java technology Jianghu has published an article with the article id of 112
  lpush msg:{tuofafaId} 112
  Finally, get the latest news or the previous messages: lrange msg:10 0 4
  The operation is shown in the figure below:
  

5, Common methods and usage scenarios of set

1. Common methods

Set Common operation
SADD key member [member ...]			//Store elements into the set key, and ignore them if they exist,
							if key New if none exists
SREM key member [member ...]			//Delete element from set key
SMEMBERS key							//Get all elements in the set key
SCARD key								//Gets the number of elements of the set key
SISMEMBER key member					//Judge whether the member element exists in the set key
SRANDMEMBER key [count]					//Select count elements from the set key, and the elements will not be deleted from the key
SPOP key [count]						//Select count elements from the set key, and delete the elements from the key

Set Arithmetic operation
SINTER key [key ...] 					//Intersection operation
SINTERSTORE destination key [key ..]	//Store the intersection results in the new set destination
SUNION key [key ..] 					//Union operation
SUNIONSTORE destination key [key ...]	//Store the union result in the new set destination
SDIFF key [key ...] 					//Difference set operation
SDIFFSTORE destination key [key ...]	//Save the difference set result into the new set destination

2.set usage scenario

• Lottery scene
  We must have participated in the lottery in our daily life. The process will not be described in detail here. In general, we must first let users join the lottery collection, that is to participate. You should also view all users participating in the lottery, and then the lottery.
  Join the raffle: sadd cj user
  View participants in the raffle: smembers cj
  Lucky draw: srandmember cj 3 or spop cj 3. The difference between the two is that the former remains in the collection after drawing the prize (you can continue to draw other prizes), and the latter has been deleted from the collection (you can't participate in other prizes)

  Join the raffle:
  
  View all users participating in the raffle:
  
  luck draw:
  

• Praise and collection of wechat microblog
  Look at a picture first
  
  This must be familiar to everyone. Circle of friends often praise others.
  Like: sadd like: {message id} {user id}
  Cancel likes: srem like: {message id} {user id}
  Check whether the user likes: sismember like: {message id} {user id}
  List of users who get likes: smembers like: {message id}
  Number of users getting likes: scar like: {message id}
  The command operation is as follows:
  

• Collection operation
  In addition, set can also complete the set operation in mathematics. Find some intersection, union and difference sets
  We design such an environment, assuming that there are three sets A, B and C. There are a,b,c in set A. b,c,d in set B. There are c,d,e in set C.
  Find the intersection of sets a, B and C: sinter a, B and C
  Find the union of sets A,B,C: Sunion A,B,C
  Find the difference set of sets A, B and C: sdiff A, B and C (return the elements of set A that do not exist in sets B and C)
  The command operation is as follows:
  

• Collection operation to realize microblog and wechat attention model
  The previous figure illustrates the focus model
  
  This scene is also very common. This is what we call the attention model. Who I pay attention to, who pays attention to me, who I pay attention to, and who we may know, are all application scenarios of set. For example:

	fafa People concerned: fafaSet-->{dt,gxr}
	suosuo People concerned: suoSet-->{dt,gxr,lmm,fafa}
	People concerned by Peng Yuan: pySet-->{dt,suosuo,lmm,fafa,nn}
	Me and suosuo People of common concern: sinter fafaSet suoSet --->{dt,gxr}
	The people I care about also pay attention to him( suosuo):
	sismember  dtSet suosuo
	sismember gxrSet suosuo
	This item may be a little windy. Careful analysis is OK. The people I care about are also concerned suosuo,Then check whether there are people in my collection suosuo. If there is, it means attention, otherwise there will be no attention.
	People I may know:
	sdiff pySet fafaSet --->{suosuo,lmm,fafa,nn}

6, Common methods and usage scenarios of zset

1. Common methods of Zset

ZADD key score member [[score member]...]	//Add elements with scores to the ordered set key
ZREM key member [member ...]				//Delete element from ordered set key
ZSCORE key member 						//Returns the score of the element member in the ordered set key
ZINCRBY key increment member			//Add increment to the score of the element member in the ordered set key 
ZCARD key								//Returns the number of elements in the ordered set key
ZRANGE key start stop [WITHSCORES]		//Obtain the elements of the ordered set key from the start subscript to the stop subscript in positive order
ZREVRANGE key start stop [WITHSCORES]	//Get the elements of the ordered set key from the start subscript to the stop subscript in reverse order

Zset Collection operation
ZUNIONSTORE destkey numkeys key [key ...]//Union calculation
ZINTERSTORE destkey numkeys key [key ...]	 //Intersection calculation

2.zset usage scenario

• zset set operation to implement Leaderboard

Use a diagram to illustrate the usage scenario:

Click news: zincrby hotNews:20211228 1 squint
Top 10 on display day: zrevrenge hotnews: 20211228 0 9 WithCores
Seven day list search calculation: ZUNIONSTORE hotNews:20211222-20211228 7
hotNews:20211222 hotNews:20211223... hotNews:20211228
Top ten in seven days:
ZREVRANGE hotNews:20211222-20211228 0 9 WITHSCORES

6, Summary

The usage scenarios of Redis are very rich. To sum up, caching, computing, and distributed locking. Because this article focuses on the common methods and actual combat scenarios of Redis data structure, a separate article will be written later for distributed locks.