This article, as a general knowledge course of Redis, aims to give you a conceptual and holistic understanding of Redis, and you can get started quickly to lay a foundation for in-depth Redis.

Article Summary:

1. The introduction of Redis
2. Redis compared to other databases
3. Redis compares with other caching implementations
4. Redis data structure type
5. The Redis command operates on several data types
6. Spring Data Redis operates on several Data types
7. Zsets (ordered sets) guarantee order
8. A SET randomly retrieves elements

The introduction of Redis

Redis is a non-relational database (NOSQL for short).

Redis is a remote in-memory database that a Redis client can request from a server over TCP.

Redis is robust and supports persistence and replication, making it easy to store and read massive amounts of data.

So just how fast is Redis? Redis comes with a tool called Redis-benchmark to simulate N clients making M requests at the same time. You can use redis-benchmark-h to check parameters.

The performance of the SET and GET operations was tested one million times:

$ redis-benchmark -n 1000000 -t setThe get - 16 P - q
SET: 198098.27 requests per second
GET: 351988.72 requests per second
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Redis compared to other databases

It’s easy to “miss the forest for the trees” or “the hammer in your hand makes everything look like a nail.”

Therefore, we first do a horizontal comparison with common database systems in the market, so that you can get a more intuitive sense of Redis characteristics.

Redis compares with other caching implementations

At the same time Redis as a common cache implementation, we also compare the advantages and disadvantages of common cache implementation.

Redis data type

Before Redis 5 introduced a new Stream data type, Redis could store mappings between keys and five different data structure types. The five data structure types are STRING, LIST, SET, HASH, and ZSET.

An overview of Redis’s five data types

The Redis command operates on five data types

STRING command

String manipulation

For strings, Redis supports the most basic SET GET and DEL operations. It also supports many complex operations, which are briefly described below.

Here’s a quick demonstration of how Command operates on strings:

127.0.0.1:6379> GET key-string
(nil)
127.0.0.1:6379> SET key-str "my string value"OK 127.0.0.1:6379 > GET key - STR"my string value"127.0.0.1:6379 > DEL key - STR (integer) 1
127.0.0.1:6379> GET key-str
(nil)
127.0.0.1:6379>
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SETEX and SETNX

SETEX and SETNX are useful for distributed locking.

Here’s an example of a SETEX application:

When a distributed session is implemented, a specified expiration time is set when the user logs in. Each time a user requests an interface, the expiration time is reset. A distributed session is invalidated when no interface is invoked within a specified period of time.

Digital operation

The following operations are supported for numbers:

Here is a brief demonstration of Command:

127.0.0.1:6379> SET key-num 0
OK
127.0.0.1:6379> INCR key-num
(integer) 1
127.0.0.1:6379> GET key-num
"1"127.0.0.1:6379 > INCR key - num (integer) 2
127.0.0.1:6379> GET key-num
"2"127.0.0.1:6379 > INCR key - num (integer) 3
127.0.0.1:6379> GET key-num
"3"
127.0.0.1:6379> INCRBY key-num 100
(integer) 103
127.0.0.1:6379> GET key-num
"103"
127.0.0.1:6379> INCRBY key-num 100
(integer) 203
127.0.0.1:6379> DECR key-num
(integer) 202
127.0.0.1:6379> DECRBY key-num 100
(integer) 102
127.0.0.1:6379> DECRBY key-num 100
(integer) 2
127.0.0.1:6379> DECRBY key-num 100
(integer) - 98.Copy the code

The batch operation

127.0.0.1:6379> MSET a 1 b 2 c 3
OK
127.0.0.1:6379> MGET a b c
1) "1"
2) "2"
3) "3"127.0.0.1:6379> MSETNX a 1 b 2 c 3integer0 127.0.1:6379 > MSETNX a 1 b 2 d 4 (integer) 0 127.0.1:6379 > MSETNX d 4 e 5 (integer6379 > 1 127.0.0.1) :Copy the code

BIT operation

The LIST command

One of the unique features of Redis is that it supports a linked list structure. The following are the operation commands for the linked list structure. It is important to be familiar with these commands to master the Redis linked list structure.

127.0.0.1:6379> LPUSH list1 1
(integer) 1
127.0.0.1:6379> RPOP list1
"1"
127.0.0.1:6379> RPOP list1
(nil)
127.0.0.1:6379> BRPOP list1 10
(nil)
(10.10s)
127.0.0.1:6379>
127.0.0.1:6379> LPUSH list1 1 2 3 4 5
(integer) 5
127.0.0.1:6379> LSET list1 4 50
OK
127.0.0.1:6379> LSET list1 5 50
(error) ERR index out of range
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BLPOP BRPOP BRPOPLPUSH is blocking and is usually used in message queues.

The SET command

Redis’ Set is an unordered collection of type String. Collection members are unique, which means that no duplicate data can occur in the collection.

The collection in Redis is realized by hash table, so the complexity of adding, deleting and searching is O(1).

Redis limits each key to 512 MEgabytes of data, and the maximum number of members in a collection is 232-1 (4294967295, each collection can store more than 4 billion members).

127.0.0.1:6379 > SADDset1 a b c d e
(integer) 127.0.0.1:6379 > SCARDset
(integer) 0 127.0.0.1:6379 > SCARDset1
(integer) 127.0.0.1:6379 > SISMEMBERset1 f
(integer) 0 127.0.0.1:6379 > SISMEMBERset1 e
(integer127.0.0.1) 1:6379 > SMEMBERSset1, 1)"d"
2) "c"
3) "a"
4) "b"
5) "e"127.0.0.1:6379 > SPOPset1
"d"127.0.0.1:6379 > SPOPset1
"a"127.0.0.1:6379 > SMOVEset1 set2 b
(integer127.0.0.1) 1:6379 > SMOVEset1 set2 c
(integer127.0.0.1) 1:6379 > SMEMBERSset2 (1)"b"
2) "c"
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SPOP, due to its randomness, can be used as a base implementation for business scenarios such as lottery programs.

HASH commands

Redis Hash is a mapping table of fields and values of string type. Similar to the Map structure in the Java language, Hash is especially suitable for storing objects.

127.0.0.1:6379 > HSET User001 name"Tom"
(integer) 1
127.0.0.1:6379> HSET User001 birthday "1990-01-20"
(integer) 1
127.0.0.1:6379> HSET User001 gender "Man"
(integer) 1
127.0.0.1:6379> HKEYS User001
1) "name"
2) "birthday"
3) "gender"127.0.0.1:6379 > HGETALL User001 1)"name"
2) "Tom"
3) "birthday"
4) "1990-01-20"
5) "gender"
6) "Man"
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ZSET command

Ordered collections, like hashes, are used to store key-value pairs. The keys of an ordered set are called members, and each member is different; The value of an ordered set is called a score, and the score must be a floating point number.

127.0.0.1:6379> ZADD Users 1 zhangsan 2 lisi 3 wangwu 4 maliu
(integer) 4
127.0.0.1:6379> ZCARD Users
(integer) 4
127.0.0.1:6379> ZRANK Users maliu
(integer) 3
127.0.0.1:6379> ZSCAN Users 0
1) "0"
2) 1) "zhangsan"
   2) "1"
   3) "lisi"
   4) "2"
   5) "wangwu"
   6) "3"
   7) "maliu"
   8) "4"127.0.0.1:6379 >Copy the code

conclusion

This article introduces you to Redis, and gives you a comprehensive understanding of Redis features and functions through horizontal comparison. Then we introduce five basic data structures of Redis in turn, and the commands to operate it. As an introduction to Redis, this article aims to give you a conceptual and holistic understanding of Redis and lay the foundation for further study of Redis.

Today, I only take you to understand the tip of the iceberg of Redis knowledge graph. I hope that with our joint efforts, we can constantly improve our skill graph and build our knowledge system together, so as to be proud in this era of algorithm and intelligence.

A link to the

The author resources

• Use of Redis pipeline technology
• Java Cache analysis

The resources

• Redis Benchmarks

• Redis Tutorial