Redis strings command

Redis And Strings command

In the previous article, we were introducing Redis The data type of , The basic commands of various data types are introduced , In this article , We will introduce these data type commands in detail

Strings

We know Strings Data types can store various strings , Then let's introduce it Strings Related commands

APPEND

edition ： >= 2.0.0
grammar ：APPEND key value
Return results ： The length of the string after the append operation
semantics ：

• If key Already exist , also key The value of is a string , The value is appended to the end of the string ; If the value is not a string , It will give an error prompt ：WRONGTYPE Operation against a key holding the wrong kind of value
• If key non-existent , I'm going to create one key, And set its value to an empty string , Then append the value to the end of the string , The command execution result in this case is equivalent to set command

> append k3 v3

because k3 non-existent , So the result is , establish k3, And set its value to an empty string , Then append the value to the end of the string .

> append k3 aaa

because k3 Already exist , So you splice the values directly to the end of the string .

DECR

edition ： >= 1.1.0
grammar ：DECR key
Return results ： reduce 1 After the value of
semantics ：

• If key There is , And the value is a string of integer type , Then subtract its value 1. If the value is not a string of integer type , May be an error ：ERR value is not an integer or out of range.
• If key non-existent , Set its value to before execution 0, Then subtract 1.
• The command is atomic

> decr k3
ERR value is not an integer or out of range

> decr k4
-1

DECRBY

edition ： >= 1.1.0
grammar ：DECRBY key decrement
Return results ： reduce decrement After the value of
semantics ： Be similar to DECR command

• If key There is , And the value is a string of integer type , Then subtract its value decrement. If the value is not a string of integer type , May be an error ：ERR value is not an integer or out of range.
• If key non-existent , Set its value to before execution 0, Then subtract decrement.
• The command is atomic

> decrby myaa 10
-10

GET

edition ： >= 1.1.0
grammar ：GET key
Return results ： key Corresponding value
semantics ：

• If key There is , And the value is of string type , Return value , If the value is not a string , False report ：WRONGTYPE Operation against a key holding the wrong kind of value
• If key non-existent , Then return to null

> set myaa bb
OK
> get myaa
bb

GETDEL

edition ： >= 6.2.0
grammar ：GETDEL key
Return results ： return key Corresponding value
semantics ：

• obtain key Value , And will key Delete
• If key non-existent , Then return to null
• If key The value of is not a string , False report ：WRONGTYPE Operation against a key holding the wrong kind of value

> set myaa bb
OK
> getdel myaa
bb

GETEX

edition ： >= 6.2.0
grammar ：GETEX key [ EX seconds | PX milliseconds | EXAT unix-time-seconds | PXAT unix-time-milliseconds | PERSIST]
Return results ： return key Corresponding value
semantics ：

• obtain key Value , And set up key The expiration time of .
• ex： Indicates the expiration time in seconds
• px： Indicates the expiration time in milliseconds
• persist： Indicates to remove the expiration time
• If key non-existent , Then return to null
• If key The value of is not a string , False report ：WRONGTYPE Operation against a key holding the wrong kind of value

> set myaa bb
OK
> getex myaa ex 50
bb

GETRANGE

edition ： >= 2.4.0
grammar ：GETRANGE key start end
Return results ： return key The string of a specified range of values
semantics ：

• Get the string of the specified range
• start and end Value , It can be either positive or negative , among -1 Represents the first string starting from the tail , And so on ,-2 Is the second string starting from the tail .
• If start and end The range of exceeds the length limit of the string , Then return to ""

> set mykey hello
OK
> getrange mykey 0 -1
hello
> getrange mykey 0 2
hel
> getrange mykey -2 -1
lo
> getrange mykey 6 10
""

GETSET

edition ： >= 1.0.0
grammar ：GETSET key value
Return results ： return key Value
semantics ：

• obtain key The old value , And set the new value
• The command is atomic

> getset mykey world
hello

INCR

edition ： >= 1.0.0
grammar ：INCR key
Return results ： Add 1 After the value of
semantics ：

• If key There is , And the value is a string of integer type , Then add its value 1. If the value is not a string of integer type , May be an error ：ERR value is not an integer or out of range.
• If key non-existent , Set its value to before execution 0, Then add 1.
• The command is atomic

> incr k3
ERR value is not an integer or out of range

> incr k4
1

INCRBY

edition ： >= 1.0.0
grammar ：INCRBY key increment
Return results ： Add increment After the value of
semantics ： Be similar to INCR command

• If key There is , And the value is a string of integer type , Then add its value increment. If the value is not a string of integer type , May be an error ：ERR value is not an integer or out of range.
• If key non-existent , Set its value to before execution 0, Then add increment.
• The command is atomic

> incrby myaa 10
10

INCRBYFLOAT

edition ： >= 2.6.0
grammar ：INCRBYFLOATkey increment
Return results ： Add increment After the value of
semantics ： Be similar to INCRBY command

• If key There is , And the value is a string of integer type , Then add its value increment. If the value is not a string of integer type , May be an error ：ERR value is not a valid float.
• If key non-existent , Set its value to before execution 0, Then add increment.
• Last 0 By default... Will be deleted
• The command is atomic

> INCRBYFLOAT myaa 10.020
10.02

LCS

edition ： >= 7.0.0
grammar ：LCS key1 key2 [LEN] [IDX] [MINMATCHLEN len] [WITHMATCHLEN]
Return results ： Evaluate the similarity of two strings
semantics ：

• LCS The implementation is the longest common subsequence algorithm

> set k1 mytext1
OK
> set k2 mynewtext2
OK
> lcs k1 k2
mytext

MGET

edition ： >= 1.0.0
grammar ：MGET key [key ...]
Return results ： Returns all specified key Value
semantics ：

• Back to all key Value
• For values that are not string type key Or it doesn't exist key, return null

> set k1 v1
OK
> set k2 v2
OK
> lpush k3 v3
1
> mget k1 k2 k3
v1
v2
null

MSET

edition ： >= 1.0.1
grammar ：MSET key value [ key value ...]
Return results ： ok
semantics ：

• Batch settings key Value
• If key Already exist , But its value type is not string , The original value will be overwritten
• The command is atomic

> mset k1 v11 k2 v22 k3 v33
OK
> mget k1 k2 k3
v11
v22
v33

MSETNX

edition ： >= 1.0.1
grammar ：MSETNX key value [ key value ...]
Return results ： be-all key Set successfully returned 1, Otherwise return to 0
semantics ：

• Batch settings key Value , If key non-existent
• As long as there is one key There is , Then the command will not perform any operation
• The command is atomic

> msetnx k1 v1 k2 v2
1
> mget k1 k2
v1
v2
> msetnx k2 v22 k3 v3
0
> mget k1 k2 k3
v1
v2
null

PSETEX

edition ： >= 2.6.0
grammar ：PSETEX key milliseconds value
Return results ： ok
semantics ：

• Set up key Value , Also set expiration time , The unit is millisecond

> psetex k3 1000 v3
OK

SET

edition ： >= 1.0.0
grammar ：SET key value [ NX | XX] [GET] [ EX seconds | PX milliseconds | EXAT unix-time-seconds | PXAT unix-time-milliseconds | KEEPTTL]
semantics ：

• Set up key Value , And can attach a series of conditions , Such as expiration date ,key Whether there is, etc
• If key Already exist , No matter key What data type is the value of , Its value will be overwritten
• NX： stay key In the absence of , Set up key
• XX： stay key In the presence of , Set up key
• GET： If key The value of is a string type , Then return to key The old value , If key Value of is not of string type , False report , If key non-existent , Then return to null
• EX seconds： Set up key The expiration time of , The unit is seconds
• PX milliseconds： Set up key The expiration time of , In milliseconds

> set k3 v3
OK
#  Set expiration time 
> set k3 v3 ex 60
OK

SETEX

edition ： >= 2.0.0
grammar ：SETEX key seconds value
semantics ：

• Set up key At the same time , Set expiration time
• The command is atomic

> set k3 1000 v3
OK

SETNX

edition ： >= 1.0.0
grammar ：SETNX key value
semantics ：

• If key non-existent , Then set the value , And the return value is 1
• If key There is , The value is not set , And the return value is 0

> setnx k5 v5
1
> setnx k5 v55
0

SETRANGE

edition ： >= 2.2.0
grammar ：SETRANGE key offset value
semantics ：

• from offset The offset starts overwriting the string , If the offset exceeds the length of the string , Then use zero-bytes fill
• Maximum offset offset by 2^29 -1 (536870911), because Redis The string size of is limited to 512MB

> set k6 v6
OK
> setrange k6 1 aaaaaa
7
> get k6
vaaaaaa
> setrange k6 8 bbb
11
> get k6
vaaaaaabbb

STRLEN

edition ： >= 2.2.0
grammar ：STRLEN key
semantics ：

• If key There is , Its value is the string , The length of the string value is returned , If the value is not a string , False report
• If key non-existent , Then return to 0

# key There is , And the value is a string 

> strlen k6
11
# key non-existent 
> strlen k7
0

That's all Strings The data type command introduces

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