Redis: operation commands for list type data

 

list （List）

Redis List is a simple list of strings , Sort by insertion order , On the left （ Head ）、 On the right （ The tail ） Or you can add elements in the middle . The operation of linked list, whether head or tail, is very efficient , But if you operate on intermediate elements , Then the efficiency will be greatly reduced .

The general idea of list type data operation is through key And subscript operations value,key It's a data ID , The subscript is the position of the data in the list ,value This is the business data we are interested in .

 

1.lpush

grammar ：lpush key value [value…]

function ： Put one or more values value Insert into list key On the far left of （ Header ）, each value Values are inserted into the header position in turn .

Return value ： The length of the inserted list .

for example ：

 

 

2.lrange

 

grammar ：lrange key startIndex endIndex

function ： To obtain a list of key Specifies the elements within the subscript interval in , Subscript from 0 Start , Length to list -1; The subscript can also be negative , Indicates that the list is taken from the back to the front ,-1 Represents the last but one element ,-2 That's the penultimate element , And so on ;startIndex and endIndex Out of range, no error will be reported .

Return value ： Get the list of elements .

  for example ： obtain list01 1 To 2 The elements of ：

 

 

3.rpush

grammar ：rpush key value [value…]

function ： Put one or more values value Insert into list key On the far right of （ Tail ）, each  value  Values are inserted at the end of the table in order .

Return value ： The length of the inserted list .

  for example ： Put it at the end of the table One time ：abcde

Reuse lpush Deposit m and n 

 

 

4.lpop

grammar ：lpop key

function ： Remove and return to list key The first element of the head , The first element on the left side of the list .

Return value ： The value of the first element on the left side of the list ; list key non-existent , return nil.

  for example ：

 

 

5.rpop

grammar ：rpop key

function ： Remove and return to list key The first element in the tail , The first element on the right side of the list .

Return value ： The value of the first element on the right side of the list ; list key non-existent , return nil.

for example ： 

 

 

6.lindex

grammar ：lindex key index

function ： To obtain a list of key The subscript indicates index The elements of , List elements are not deleted , Just search .0 Represents the first element of the list ,1 Represents the second element of the list ;index You can also subscript negative numbers , -1 Represents the last element of the list , -2 Represents the penultimate element of a list , And so on .

Return value ：key In existence , Returns the value of the specified element ;

              Key When there is no , return nil.

for example ： Gets the specified subscript ：

 

 

7.llen

grammar ：llen key

function ： To obtain a list of key The length of

Return value ： The number , The length of the list ;key There is no return 0

  for example ：

 

 

8.lrem

grammar ：lrem key count value

function ： According to the parameters count Value , Remove the list and parameters value Equal elements ,

count >0 , Remove from the left side of the list to the right ;

count < 0 Remove from the end of the list ;

count = 0 Remove all and from the table  value  Equal value .

Return value ： The number , Number of elements removed

for example ：count=2

 

count=-1 

 

count=0

 

 

 

9.ltrim

grammar ：ltrim key startIndex endIndex

function ： Intercept key The element of the specified subscript interval , And assigned to key. Subscript from 0 Start , Up to the length of the list -1; The subscript can also be negative , Indicates that the list is taken from the back to the front ,-1 Represents the last but one element ,-2 That's the penultimate element , And so on ;startIndex and endIndex Out of range, no error will be reported .

Return value ： Execution successful return ok

 

10.lset

grammar ：lset key index value

function ： Will list key Subscript to be index The value of the element of is set to value.

function ： Set successfully returned ok ; key Nonexistence or index Out of range return error message .

 

11.linsert

grammar ：linsert key before/after pivot value

function ： Will value value Insert into list key Middle value pivot Before or after .key Nonexistence or pivot Not in the list , Do nothing .

Return value ： Command executed successfully , Returns the length of the new list . Can't find pivot return -1, key There is no return 0.