New people into the pit Redis will vomit blood summary

What is Redis

Redis is an open source, high-performance key-value storage system developed in C language, which can be approximately understood as Java Map. Redis is a NOSQL in-memory database. Its full name is Not Only SQL. In other words, it is a non-relational database, which is a good supplement to the relational database. It differs from traditional MySQL and Oracle in that it greatly improves the read and write speed by reading and writing data in memory. It can be said that Redis is an indispensable part of the database solution to solve a series of problems such as high concurrency, high availability, high scalability, big data storage and so on.

It has the following characteristics:

1. Redis supports persistent data, which can keep the data in memory in disk, and can be loaded again for use when restarting. 2. Redis not only supports simple key-value type data, but also provides the storage of string, list, set, sortedSet, hash and other data structures. 3. Redis supports data backup, namely, data backup in master-slave mode.

Redis has five key value types:

String character type
Hash Hash type
List List type
Set set type
Sortedset Type of an ordered collection

This article will be based on Redis5.0 as an example to introduce the use of Redis some related commands and stepped on the pit

Ii. Installation and startup of Redis

Environment to prepare

CentOS7 (Development Tools not installed)
Redis5.0 -rc3. Tar. Gz

The installation tutorial can be found here: www.cnblogs.com/ECJTUACM-87…

Online environment

The official website seems to offer an online Redis platform, linked here: try.redis.io/

Redis start

The front-end start

After installation according to the tutorial I provided, we just need to enter the command redis-server, the interface is as follows:

Front end stop start

Force shutdown: Ctrl+ C
Normal shutdown [root@sakura]# redis-cli shutdown

The back-end start

Because Redis does not work alone in practice, the IP address and port number in the startup and shutdown mode can be changed in the configuration file, which will be changed below.

Start the way

Copy the redis. Conf file in the decompressed redis source package to the bin directory. Just copy and paste it
Conf file, change daemonize to yes(vi redis.conf, :/daemonize search).
Redis. command line redis-server redis.conf(start with configuration file)
Check whether the startup is successful. Command line ps – aux | grep redis (direct view redis process)

If you’ve followed the tutorial I’ve provided, this process can be ignored

Close the way

Forcibly disable: kill -9 PID
Normal shutdown :redis-cli -h IP address -p port number (default port number is 6379) shutdown

In projects, it is recommended to use normal shutdown. If redis is used as a cache, the data is stored in memory. If redis is turned off normally, the memory data will be persisted locally and then closed. If the shutdown is forced, persistent operations are not performed, and some data may be lost.

The Redis client starts

Start client command :[root@sakura]# redis-cli -h IP address -p port number

Since the default IP is 127.0.0.1 and port is 6379, all we need to do is type the command redis-cli

Exit :127.0.0.1:6379> quit

Explanation of Redis data types and common commands

1, Redis – String

String Usage environment: Mainly used to save the string in JSON format

The assignment

Set key value: Sets the key to hold the specified string value, overwrites the key if it exists, always returns “OK”, if given the same key, the new value overwrites the old value

example:

127.0.0.1:6379> set username zhangsan
OK
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The values

Get key: obtains the value of the key. If the value associated with the key is not a string, redis will return an error because the get command can only be used to get a string value. If the key does not exist, return nil

example:

127.0.0.1:6379 > get the username "zhangsan"Copy the code

delete

Del key: deletes the specified key. The returned value is a number, indicating that several pieces of data are deleted

example:

127.0.0.1:6379> del username
(integer) 1
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extension

Getset Key Value: obtains the key value and then sets the key value

example:

127.0.0.1:6379> getset username zhangsan
(nil)
127.0.0.1:6379> keys *
1) "username"
127.0.0.1:6379> get username
"zhangsan"
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Incr key: increals the value of the specified key atomically by 1. If the key does not exist, the initial value is 0, and the value after incr is 1. If the value of the key cannot be converted to an integer, such as Hello, this operation fails and returns an error message, equivalent to ++. When the counter)

example:

127.0.0.1:6379> set age 18
OK
127.0.0.1:6379> incr age
(integer) 19
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Decr key: decrement the atomicity of the value of the specified key by 1. If the key does not exist, its initial value is 0, and the value after incr is -1. If the value of value cannot be converted to an integer, such as Hello, this operation fails and returns an error message, equivalent to — I

example:

127.0.0.1:6379> set age 18
OK
127.0.0.1:6379> decr age
(integer) 17
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Append Key Value: a concatenated string. If the key exists, the value is appended to the original value. If the key does not exist, a new key/value is created

example:

127.0.0.1:6379> Set information hel OK 127.0.0.1:6379> Append information LO (INTEGER) 5 127.0.0.1:6379> Get information  "hello"Copy the code

Incrby and decrby: This operation can be performed only for numeric strings. Incrby key Value adds value to the original key value, and decrby key value decreases value to the original key value

example:

127.0.0.1:6379> get age
"17"
127.0.0.1:6379> incrby age 10
(integer) 27
127.0.0.1:6379> decrby age 10
(integer) 17
127.0.0.1:6379> get information
"hello"
127.0.0.1:6379> incrby information 10
(error) ERR value is not an integer or out of range
127.0.0.1:6379> decrby information 10
(error) ERR value is not an integer or out of range
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2, Redis hash

The hash type in Redis can be regarded as a map container with string keys and string values, so it is very suitable for storing information about value objects. Such as username, password, and age. If the hash contains very few fields, that type of data will also take up very little disk space. Each hash can store 4,294,967,295 key-value pairs.

Hash features: Occupies very little disk space

Assignment:

Hset key field Value: Sets the field/value pair for the specified key.

example:

127.0.0.1:6379> hset key1 field1 123
(integer) 1
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hmset key field value[field2 value2…] : Sets multiple fields/values in the key

example:

127.0.0.1:6379> hmset aaa name kitty age 20
OK
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Values:

Hget Key filed: Field value of the specified key

example:

127.0.0.1:6379> hget key1 field1
"123"
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hmget key filed1 field2… : Gets the values of multiple fields in the key

example:

127.0.0.1:6379> hmget aaa name age
1) "kitty"
2) "20"
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Hgetall key: Gets all field-value2s in the key

example:

127.0.0.1:6379> hgetall aaa
1) "name"
2) "kitty"
3) "age"
4) "20"
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delete

hdel key field[field…] : One or more fields can be deleted. The return value is the number of fields to be deleted

example:

127.0.0.1:6379> hdel key1 field1
(integer) 1
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Del key: Deletes the entire list

example:

127.0.0.1:6379> del aaa
(integer) 1
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Increase the number

Hincrby Key field increment: Increments the field in the key, for example, age by 20

example:

127.0.0.1:6379> hmset aaa name kitty age 20
OK
127.0.0.1:6379> hincrby aaa age 20
(integer) 40
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The extension command

Hexists Key Field: checks whether the field in the specified key exists

example:

127.0.0.1:6379> hexists aaa name
(integer) 1
127.0.0.1:6379> hexists aaa aaaa
(integer) 0
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Hlen key: Gets the number of fields that the key contains

example:

127.0.0.1:6379> hlen aaa
(integer) 2
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Hkeys key: Retrieves all fields

example:

127.0.0.1:6379> hkeys aaa
1) "name"
2) "age"
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3, Redis – the list

In Redis, list is selected as a linked list, because in Redis operation, the most operation is to add and delete elements

The assignment

lpush key value [value1 value2 …] Inserts all values into the list header associated with the specified key. If the key does not exist, this command creates an empty list associated with the key before inserting it. After inserting data into the list header, the number of elements is returned.

example:

127.0.0.1:6379> Lpush score1 12 3 4 5 (integer) 5Copy the code

rpush key value [value1 value2 …] Add the element at the end of the list

example:

127.0.0.1:6379> rpush score2 12 3 4 5 (integer) 5Copy the code

The values

Lrange key start end: obtain the value of the linked list elements from start to end. Start and end are counted from 0. It can also be negative, -1 for the element at the end of the list, -2 for the next-to-last, and so on…

example:

127.0.0.1:6379> lrange score1 0-1 1) "5" 2) "4" 3) "3" 4) "2" 5) "1" 3) "3" 4) "4" 5) "5"Copy the code

Delete value

Lpop Key: Returns and pops the first element in the linked list associated with the specified key, the header element. If the key does not exist, return nil; If key is present, the head element of the list is returned

example:

127.0.0.1:6379> lpop score1
"5"
127.0.0.1:6379> lpop score2
"1"
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Rpop Key: Pops elements from the tail

example:

127.0.0.1:6379> rpop score1
"1"
127.0.0.1:6379> rpop score2
"5"
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extension

Llen key: Returns the number of elements in the linked list associated with the specified key

example:

127.0.0.1:6379> llen score1
(integer) 3
127.0.0.1:6379> llen score2
(integer) 3
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Lrem key count value: delete all elements whose value is value. If count is greater than 0, delete all elements whose value is value. If count is less than 0, delete all elements whose value is value. Delete all elements in the linked list equal to value.

example:

127.0.0.1:6379> Lrem score1 12 (integer) 1 127.0.0.1:6379> Lrem score2 12 (integer) 1Copy the code

Replace by index

Lset key Index value: Sets the value of the index element in the linked list. 0 represents the first element and -1 represents the last element. An exception is thrown if no pins exist for the operation linked list

example:

127.0.0.1:6379> lset score1 0 1
OK
127.0.0.1:6379> lset score2 0 1
OK
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Inserts elements before/after the index

Linsert key before | after the pivot value: in the pivot element inserted before or after the value of this element

example:

127.0.0.1:6379> linsert score1 before 3 AAA (integer) 3 127.0.0.1:6379> lrange score1 0-1 1) "1" 2) "aaa" 3) "3" 127.0.0.1:6379> linsert score1 after 3 BBB (integer) 4 127.0.0.1:6379> lrange score1 0-1 1) "1" 2) "aaa" 3) "3" 4) "bbb"Copy the code

Rpoplpush Resource Destination: Pops up the tail element of the linked list and adds it to the header. [Loop operation]

example:

127.0.0.1:6379> lrange score1 0-1 1) "1" 2) "aaa" 3) "3" 127.0.0.1:6379> lrange score2 0-1 1) "BBB" 2) "1" 3) "4" 127.0.0.1:6379> rpoplpush score1 score2 "3" 127.0.0.1:6379> lrange score1 0-1 1) "1" 2) "aaa" 127.0.0.1:6379> lrange score2 0 -1 1) "3" 2) "bbb" 3) "1" 4) "4"Copy the code

4, Redis – set

The assignment

sadd key value[value1 value2…] : Adds elements to a set, not if the key already has a value

example:

127.0.0.1:6379> sadd ABC 12 3 4 (integer) 4Copy the code

srem key member[member1 member2…] : Deletes the member specified in set

example:

127.0.0.1:6379> srem abc 1 3
(integer) 2
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The values

Smembers key: Gets all the members in a set

example:

127.0.0.1:6379> smembers abc
1) "2"
2) "4"
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Sismember key member: Checks whether the specified member is in the set. 1 means it exists, 0 means it does not exist, or the key itself does not exist.

example:

127.0.0.1:6379> sismember abc 2
(integer) 1
127.0.0.1:6379> sismember abc 3
(integer) 0
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Delete value

Set operations

Difference set operation

sdiff key1 key2… : Returns the members of key1 that differ from key2, depending on the order of the keys, i.e. the difference set

example:

127.0.0.1:6379> sadd set1 12 3 4 5 (integer) 5 127.0.0.1:6379> sadd set2 3 4 5 6 7 (integer) 5 127.0.0.1:6379> sdiff Set1 set2 1) "1" 2) "2" 127.0.0.1:6379> sdiff set2 set1 1) "6" 2) "7"Copy the code

Intersection operation

sinter key1 key2… : Return intersection

example:

127.0.0.1:6379> sinter set1 set2
1) "3"
2) "4"
3) "5"
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And set operation

sunion key1 key2… : Returns the union

example:

127.0.0.1:6379 > sunion characters set2 1) "1" 2) "2" 3) "3" 4) "4" 5) "5" 6) "6" 7) "7"Copy the code

The extension command

Scard key: Gets the number of members in the set

example:

127.0.0.1:6379> scard set1
(integer) 5
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Srandmember Key: Returns a random member of the set

example:

127.0.0.1:6379> srandmember set1
"1"
127.0.0.1:6379> srandmember set1
"5"
127.0.0.1:6379> srandmember set1
"3"
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sdiffstore destination key1 key2… Will: key1 key2… The offset members are stored at the destination

example:

127.0.0.1:6379> sdiffStore set3 set1 set2 (integer) 2 127.0.0.1:6379> smembers set3 1) "2"Copy the code

sinterstore destination key[key…] : stores the returned intersection at destination

example:

127.0.0.1:6379> sinterstore set4 set1 set2
(integer) 3
127.0.0.1:6379> smembers set4
1) "3"
2) "4"
3) "5"
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5, Redis – sortedset

The assignment

zadd key score member score2 member2… : stores all members and their scores in a sorted-set. If the element already exists, the new fraction is used to replace the original fraction. The return value is the number of elements added to the collection, excluding pre-existing elements.

example:

127.0.0.1:6379> zadd list 50 xiaoming 100 xiaohong 200 xiaozhang
(integer) 3
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The values

Zscore key member: Returns the score of a specified member

example:

127.0.0.1:6379> zscore list xiaohong
"100"
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Zcard key: Gets the number of members in the collection

example:

127.0.0.1:6379> zcard list
(integer) 3
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Range queries

Zrange key start end[withscores]: returns a member of the set with start-end, withscores

example:

127.0.0.1:6379> zrange list 0-1 withscores 1) "xiaoming" 2) "xiaohong" 3) "xiaozhang" 127.0.0.1:6379> zrange list 0-1 withscores 1) "xiaoming" 2) "50" 3) "xiaohong" 4) "100" 5) "xiaozhang" 6) "200"Copy the code

Zrevrange key start end[withscores]: Retrieves a member of the set with start-end. The parameter [withscores] indicates that the returned member contains its score.

example:

127.0.0.1:6379> zrevrange list 0-1 1) "xiaozhang" 2) "xiaohong" 3) "xiaoming" 127.0.0.1:6379> zrevrange list 0-1 withscores 1) "xiaozhang" 2) "200" 3) "xiaohong" 4) "100" 5) "xiaoming" 6) "50"Copy the code

Delete value

zrem key member[member…] : Removes a specified member from the collection. You can specify multiple members

example:

127.0.0.1:6379> zrem list xiaozhang
(integer) 1
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Zremrangebyrank key start stop: deletes elements byrank range

example:

127.0.0.1:6379> zremrangebyrank list 0 1
(integer) 2
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Zremrangebyscore key min Max: deletes elements according to the score range

example:

127.0.0.1:6379> zremrangebyscore list 50 120
(integer) 2
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The extension command

Zrangebyscore key min Max [withscores][LIMIT offset count]: returns the members whose scores are in [min, Max] and sorts them byscore from lowest to highest. [withscores]: displays scores; [LIMIT offset count]:offset, starting from the element with offset and returning count members

example:

127.0.0.1:6379> zrangebyScore list 50 withscores limit 0 2 1) "xiaoming" 2) "50" 3) "xiaohong" 4) "100"Copy the code

Zincrby key Increment Member zincrby Key increment Member Zincrby Key increment Member Zincrby Key increment Member zincrby Key increment Member

example:

127.0.0.1:6379> zincrby list 30 xiaoming
"80"
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Zcount key min Max: Gets the member whose score is between [min, Max]

example:

127.0.0.1:6379> zcount list 80 120
(integer) 2
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Zrank key member: returns the rank of the member in the set (index from small to large).

example:

127.0.0.1:6379> zrank list xiaohong
(integer) 1
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Zrevrank Key Member: Returns the rank of the member in the collection. (Index from largest to smallest)

example:

127.0.0.1:6379> zrevrank list xiaozhang
(integer) 0
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6. General Redis command

Keys pattern: Retrieves all keys that match the pattern and returns all keys that match the key. * indicates any one or more characters

Wild card:

* indicates zero or more characters
? Represents any character

Exits key: checks whether the key exists. 1 indicates that the key exists, and 0 indicates that the key does not exist

example:

127.0.0.1:6379> exists username
(integer) 1
127.0.0.1:6379> exists admin
(integer) 0
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Rename Key newkey: Renames the current key

127.0.0.1:6379> rename username user
OK
127.0.0.1:6379> keys *
 1) "list"
 2) "abc"
 3) "set1"
 4) "information"
 5) "set2"
 6) "age"
 7) "score2"
 8) "set4"
 9) "score1"
10) "set3"
11) "user"
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Type key: Gets the value type of the specified key. This command is returned as a string. The returned strings are string, list, set, hash, and zset, or None if key does not exist

example:

127.0.0.1:6379> type user
string
127.0.0.1:6379> type list
zset
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Expire key: Sets the expiration time, in seconds. If a key expires, Redis will delete it

example:

127.0.0.1:6379> expire ABC 10 (integer) 1 127.0.0.1:6379> keys * 1) "list" 2) "set1" 3) "information" 4) "set2" 5) "age"  6) "score2" 7) "set4" 8) "score1" 9) "set3" 10) "user"Copy the code

TTL key: obtains the remaining timeout period of the key. If the timeout period is not set, -1 is returned. If -2 is returned, the timeout does not exist.

example:

127.0.0.1:6379> expire user 10
(integer) 1
127.0.0.1:6379> ttl user
(integer) 3
127.0.0.1:6379> ttl user
(integer) -2
127.0.0.1:6379> keys *
1) "list"
2) "set1"
3) "information"
4) "set2"
5) "age"
6) "score2"
7) "set4"
8) "score1"
9) "set3"
127.0.0.1:6379> ttl information
(integer) -1
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7. Other Redis features

Message subscription and publishing

We subscribe channel

example:

127.0.0.1:6379> subscribe mychat
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "mychat"
3) (integer) 1
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Psubscribe Channel *: bulk subscription channel

example:

127.0.0.1:6379> SUBSCRIBE s* Reading messages... (press Ctrl-C to quit) 1) "psubscribe" 2) "s*" 3) (integer) 1Copy the code

Publish Channel Content: Publishes messages in the specified channel

example:

127.0.0.1:6379> publish mychat 'today is a newday'
(integer) 1
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Many database

Traditional databases such as MySQL databases can be created in their own terms, we can create database XXXX to create. Redis also has a database, but Redis has already created it in advance. There are sixteen databases in redis by default, 0,1,2…. 15. All data operations performed on radis are performed on database 0 by default, and key-value pairs cannot be shared between databases. We can think of the Redis database as a map collection.

Switching databases

Select database name: switch database

example:

127.0.0.1:6379> SELECT 1 OK 127.0.0.1:6379[1]> SELECT 15 OK 127.0.0.1:6379[15]> SELECT 16 (error) ERR DB index is out of  rangeCopy the code

Database migration

Move NewKey Database name: Migrates the key of the current database to the specified database

example:

127.0.0.1:6379> keys *
1) "list"
2) "set1"
3) "information"
4) "set2"
5) "age"
6) "score2"
7) "set4"
8) "score1"
9) "set3"
127.0.0.1:6379> move information 1
(integer) 1
127.0.0.1:6379> keys *
1) "list"
2) "set1"
3) "set2"
4) "age"
5) "score2"
6) "set4"
7) "score1"
8) "set3"
127.0.0.1:6379> select 1
OK
127.0.0.1:6379[1]> keys *
1) "information"
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Clearing the database

Flushdb Deletes all keys in the current database

Flushall Deletes all keys from all databases

Server command

Ping tests whether the connection is alive

example:

127.0.0.1:6379 > ping PONGCopy the code

Echo prints something on the command line

example:

127.0.0.1:6379 > echo hehe "hehe"Copy the code

Quit /Ctrl+C Exits the client

example:

127.0.0.1:6379 > quitCopy the code

Dbsize returns the number of keys in the current database

example:

127.0.0.1:6379 > dbsize (integer) 8Copy the code

Info Displays server information and statistics

example:

127.0.0.1:6379> info # Server redis_version:4.9.103 redis_git_sha1:00000000 redis_git_dirty:0 redis_build_id:d727e4f6fe88cefd redis_mode:standalone ...... .Copy the code

8. Redis Persistence strategy

RDB strategy

RDB is the default persistence mechanism of Redis. It is equivalent to taking snapshots to save a state

Advantages:

The snapshot speed is very fast and the data restoration speed is very fast
Applicable to disaster backup

Disadvantages:

Small memory machines are not suitable for use

If the RDB mechanism meets the requirements, snapshots will be taken (started at any time and anywhere), which will occupy certain system resources (suddenly) and may break down directly due to insufficient memory. (After the outage, the server will shut down, which is abnormal shutdown and data will be lost)

The RDB mechanism is suitable for computers with plenty of memory

When does the RDB take a snapshot?

When the server is shut down, a snapshot is taken
If the key meets certain conditions, a snapshot is taken
- Save 900 1# If at least one key changes every 900 seconds, the memory snapshot is dumped
- Save 300 10# Dump memory snapshot if at least 10 keys change every 300 seconds
- Save 60 10000# Dump memory snapshot if at least 10000 keys change every 60 seconds

AOF strategy

The AOF policy uses the log function to save data operations. By default, the AOF mechanism is disabled and only the statements that cause key changes are saved

Advantages:

Use very little memory resources continuously

Disadvantages:

Log files can be too large for disaster recovery
The recovery efficiency is much lower than RDB

The AOF mechanism is suitable for computers with small memory

How does AOF back up data?

Synchronization per second: AOF is performed once every second to save data, which has low security and saves system resources
Each change synchronization: As long as there is a key change statement, the AOF saves data. It is relatively safe, but it wastes system resources and reduces efficiency
Out of sync: There is no persistence. This configuration is not secure

AOF the configuration of the

Always # Write to AOF files every second when data changes occur
Everysec # synchronizes once per second, which is the default policy for AOF
No # is never synchronized. Efficient but data is not persisted

Method to enable AOF mechanism

Use :/aof to find the corresponding paragraph in the redis.config file
Change appendOnly no to appendOnly yes
Add appendfsync always to appendfsync

New people into the pit Redis will vomit blood summary

New people into the pit Redis will vomit blood summary

What is Redis

Redis has five key value types:

Ii. Installation and startup of Redis

Environment to prepare

Online environment

Redis start

The front-end start

Front end stop start

The back-end start

The Redis client starts

Explanation of Redis data types and common commands

1, Redis – String

The assignment

The values

delete

extension

2, Redis hash

Assignment:

Values:

delete

Increase the number

The extension command

3, Redis – the list

The assignment

The values

Delete value

extension

Replace by index

Inserts elements before/after the index

4, Redis – set

The assignment

The values

Delete value

The extension command

5, Redis – sortedset

The assignment

The values

Range queries

Delete value

The extension command

6. General Redis command

7. Other Redis features

Message subscription and publishing

Many database

Switching databases

Database migration

Clearing the database

Server command

8. Redis Persistence strategy

RDB strategy

AOF strategy

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