Basic concept and usage of redis

Redis

Redis What is it?

• Open source （BSD agreement ）, Use ANSI C To write , Memory based and persistent , High performance Key-Value Of NoSQL database .
• Support data structure type rich , Like a character string （strings）, hash （hashes）, list （lists）, aggregate （sets）, Ordered set （sorted sets） And scope query , bitmaps, hyperloglogs and Geographical space （geospatial） Index radius query .
• Rich client support for mainstream languages ,C、C++、Python、Erlang、R、C#、Java、PHP、Objective-C、Perl、Ruby、Scala、Go、JavaScript.
• purpose ： cache 、 database （ Microblogging ）、 Message middleware （ Microblogging ）
• Official website ：https://redis.io

---

NoSQL classification

Redis Data model

key Key

• Redis key Values are binary safe , This means that any binary sequence can be used as key value , From the shape as ”foo” A simple string to a JPEG The content of the document can be . Empty strings are also valid key value .
• Key Value principle
  • The key does not need to be too long , Memory consumption , And the calculation cost of finding such key value in the data is higher
  • The key value should not be too short , Poor readability

String

• String is one of the most basic Redis Value type .Redis Strings are binary safe , This means a Redis A string can contain any type of data
  • for example ： a sheet JPEG Format picture or a serialized Ruby object
• A string type value can store up to 512M The contents of bytes

command

Get help after logging in to the client

• Help
• Help
• Help set
• Help @string

Help

help

Help set

help set

Help @string

help @string

Set string value

• SET key value [EX seconds] [PX milliseconds] [NX|XX]
  • EX Set expiration time , second , Equate to SETEX key seconds value
  • PX Set expiration time , millisecond , Equate to PSETEX key milliseconds value
  • NX The key doesn't exist , To set , Equate to SETNX key value
  • XX When the bond exists , To set

Here we mainly know CRUD（ Add, delete, change and delete ）

set K V

#set K V
set name  handsome young man 

# check     The result here is 16 Binary stored 
get name

set age 20

get age

Be overdue

• Redis You can give to Key Set a lifetime （ Seconds or milliseconds ）, When this time is reached , These key values will be automatically deleted
• Set how many seconds or milliseconds to expire
  • EXPIRE key seconds
  • PEXPIRE key milliseconds
• Set to specify Unix Time stamp expired
  • EXPIREAT key timestamp
  • PEXPIREAT key milliseconds-timestamp
• Delete expired
  • PERSIST key

set K V NX

NX The key doesn't exist , To set , Equate to SETNX key value

set score 100 NX

get score

set age 23

get age

set age 24 NX

get age

set K V [EX|PX]

#EX  In seconds , It means how many seconds you only survive ,5 The value cannot be obtained after seconds 
set ttl dead EX 5

get ttl
get ttl

#PX  In milliseconds , It means how many milliseconds it only survives ,5000 The value cannot be obtained after milliseconds 
set ttl dead PX 5000

get ttl
get ttl
get ttl

This command is suitable for hot search cache , The survival time will expire as soon as it passes , There is no need to keep this data forever

Set string values for multiple keys

• MSET key value [key value …]

mset k1 v1 k2 v2 k3 v3

get k1
get k2
get k3

When the key doesn't exist , Set string value

• MSETNX key value [key value …]
• Be careful ： This is an atomic operation

multi
set k4 v4
set k5 v5
set k6 v6

get k1
get k4

exec
get k1
get k2
get k4
get k5

multi
set k7 v7
set k8 v8
DISCARD
get k7

EXPIRE Be overdue

EXPIRE k4 6
get k4
#  etc. 6 second 
get k4

#  When the timestamp reaches this time, it will expire 
EXPIREAT k2 1642778319
get k2
get k2
get k2

Delete expired PERSIST KEY

expire k3 11
PERSIST k3

get k3
#  Wait for the command to execute 11 Second to view the data 
get k3

Time to live

• Time To Live,Key The remaining lifetime of

Check the remaining lifetime

• TTL key
• PTTL key
• key Exists but not set TTL, return -1
• key There is , But it's still alive , Returns the remaining seconds or milliseconds
• key Once existed , But it's dead , return -2(2.8 Return before version -1)

Lookup key

• KEYS pattern

pattern Value

• Any length of characters
  ? Any character
  [] Character set , The representation can be any one of the sets

KEYS pattern

#  Here is the idea of regular expressions 
keys k*
keys k?

keys k[1365]

keys ??

Key type

• TYPE key

Does the key exist

• EXISTS key

The key to rename

• RENAME key newkey
• RENAMENX key newkey

Key delete

• DEL key [key …]

Get value

• GET key

Get the values of multiple given keys

• MGET key [key …]

Returns the old value and sets the new value

• GETSET key value
• If the key doesn't exist , Create and assign

String length

• STRLEN key

Append string

• APPEND key value
• If the key exists, append ; If it does not exist, it is equivalent to SET key value

Get substring

• GETRANGE key start end
• Index value from 0 Start , A negative number means counting from the right to the left of the string ,-1 Indicates that there is one character at most

Override string

• SETRANGE key offset value

step

step 1 Increase and decrease of

• INCR key
• DECR key
• The string value will be interpreted as 64 Bit signed decimal integer to operate , The result is still converted to a string

Step increase or decrease

• INCRBY key decrement
• DECR key decrement
• The string value will be interpreted as 64 Bit signed decimal integer to operate , The result is still converted to a string

Bitmap bitmap

• Bitmaps are not really data types , It is defined in a string type
• A string type value can store up to 512M The contents of bytes
• Bit upper limit ：2^{(9+10+10+3)=2}32b

Set the value of a bit

• SETBIT key offset value
• offset Offset , from 0 Start
• value Don't write , The default is 0

Get the value of a bit

• GETBIT key offset

Returns the specified value 0 perhaps 1 The position of the first occurrence on the specified interval

• BITPOS key bit [start] [end]

Bit operation

• For one or more strings that hold binary bits key Perform bit operation , And save the result to dteskey On
• operation It can be AND 、 OR 、 NOT 、 XOR Any of the four operations
• BITOP AND destkey key [key …] , To one or more key Seek logic and , And save the result to destkey
• BITOP OR destkey key [key …] , To one or more key Seek logic or , And save the result to destkey
• BITOP XOR destkey key [key …] , To one or more key Seek logical XOR , And save the result to destkey
• BITOP NOT destkey key , For given key Logic is not , And save the result to destkey
• except NOT Out of operation , Other operations can accept one or more key As input
• When BITOP When dealing with strings of different lengths , The missing part of the shorter string will be treated as 0
• Empty key It is also seen as containing 0 String sequence of
• reflection ：a Bit or b What is it? ？

Statistics means that the value on the positioning interval is 1 The number of

• BITCOUNT key [start] [end]
• From left to right 0 Start , From right to left -1 Start , Pay attention to the official start、end Yes , After the test is byte
• BITCOUNT testkey 0 0 Indicates from index to 0 Bytes to index 0 Bytes , Is the statistics of the first byte
• BITCOUNT testkey 0 -1 Equate to BITCOUNT testkey
• The most common is BITCOUNT testkey

Redis Binary bit of

Log in to different libraries

• redis-cli --help
• redis-cli -n 2

Clear current data

• FLUSHDB

Clear all data in the library

• FLUSHALL

Statistics of the maximum number of website users （ Active users ）

user ID by key, Days as offest, Set online to 1
ID by 500 Users of , This year's 1 Skyline 、 The first 30 Skyline

SETBIT u500 1 1
SETBIT u500 30 1
BITCOUNT u500
KYES u*

Count the active users of the website by day

 Days as key, user ID by offset, Set online to 1
 Find the number of active users in a period of time 
SETBIT 20160602 15 1
SETBIT 20160601 123 1
SETBIT 20160606 123 1
 seek 6 month 1 The day is coming 6 month 10 Active users of the day 
BITOP OR 20160601-10 20160601 20160602 20160603 20160610
BITCOUNT 20160601-10
 The result is 2