Redis data type - list list

list List（ More than one value Value）

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# lpush ： Insert one or more values into the list header （ Left ）

# rpush ： Insert one or more values at the end of the list （ Right ）

# lrange ： Returns the elements in the specified interval in the list , The interval is offset by start and end Appoint

# among 0 Represents the first element of the category    1 Represents the second element of the list And so on

# You can also use negative subscripts With -1 Represents the last element of the list -2 Represents the penultimate element of a list And so on

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127.0.0.1:6379> lpush list one
(integer) 1
127.0.0.1:6379> lpush list two
(integer) 2
127.0.0.1:6379> lpush list three
(integer) 3
127.0.0.1:6379> lrange list 0 -1
1) "three"
2) "two"
3) "one"
127.0.0.1:6379> lrange list 0 1
1) "three"
2) "two"
127.0.0.1:6379> 
 

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# lpop ： The command removes and returns the first element of the list . When category key When there is no return nil

# rpop： Remove the last element of the list , The return value is the removed element

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127.0.0.1:6379> rpush list right
(integer) 3
127.0.0.1:6379> lpop list
"two"
127.0.0.1:6379> rpop list
"right"
127.0.0.1:6379> lrange list 0 -1
1) "one"
 

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# lindex ： Get elements according to index subscript （-1 On behalf of the last   0 On behalf of the first ）

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127.0.0.1:6379> lindex list 1
(nil)
127.0.0.1:6379> lindex list 0
"one"
127.0.0.1:6379> lindex list -1
"one"
 

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# llen ： Used to return the length of the list

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127.0.0.1:6379> flushdb
OK
127.0.0.1:6379> lpush list one
(integer) 1
127.0.0.1:6379> lpush list two
(integer) 2
127.0.0.1:6379> lpush list three
(integer) 3
127.0.0.1:6379> llen list                # Returns the length of the list
(integer) 3
 

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# lrem key : According to the parameters count Value   Remove the list and parameters value Equal elements

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127.0.0.1:6379> lrem list 1 two
(integer) 1
127.0.0.1:6379> lrange list 0 -1
1) "three"
2) "one"
 

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# ltrim key : Trim a list （trim） That is to say , Let the list keep only the elements in the specified range , Elements that are not in the specified range will be removed

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127.0.0.1:6379> rpush mylist wyt
(integer) 1
127.0.0.1:6379> rpush mylist lmp
(integer) 2
127.0.0.1:6379> rpush mylist hyd
(integer) 3
127.0.0.1:6379> rpush mylist yjy
(integer) 4
127.0.0.1:6379> ltrim mylist 1 2
OK
127.0.0.1:6379> lrange mylist 0 -1
1) "lmp"
2) "hyd"
 

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# rpoplpush : Remove the last element of the list , And add the element to another list and return

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127.0.0.1:6379> rpush list hello
(integer) 1
127.0.0.1:6379> rpush list foo
(integer) 2
127.0.0.1:6379> rpush list bar
(integer) 3
127.0.0.1:6379> rpoplpush list myotherlist
"bar"
127.0.0.1:6379> lrange list 0 -1
1) "hello"
2) "foo"
127.0.0.1:6379> lrange myotherlist 0 -1
1) "bar"

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# lset key index  value : Will list Sure Subscript to be index The value of the element of is set to value

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127.0.0.1:6379> exists list                 # Empty list lset
(integer) 0
127.0.0.1:6379> lset list 0 item           # Report errors
(error) ERR no such key
127.0.0.1:6379> lpush list one           # For non empty lists lset
(integer) 1        
127.0.0.1:6379> lrange list 0 -1 
1) "one"
127.0.0.1:6379> lset list 0 new           # Update value
OK
127.0.0.1:6379> lrange list 0 0
1) "new"
127.0.0.1:6379> lset list 1 new   #index Out of range error
(error) ERR index out of range
 

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# linsert key before/after pivot value Used to insert elements before or after elements in the list .

# Will value value Insert into list key among , At value pivot Before or after .

# ===================================================

Performance summary

1. It's a list of strings ,left,right You can insert and add
2. If the key doesn't exist , Create a new list
3. If the key already exists , The new content
4. If all values are removed , The corresponding bond disappears
5. The operation of linked list is very efficient both in head and tail , But if it is to operate on the intermediate elements , The efficiency is very poor

list It's a list , Anyone with a little knowledge of data structure should be able to understand its structure . Use Lists structure , We can easily achieve the latest news ranking and other functions .List Another application of is message queuing , You can use List Of PUSH operation , Keep the task alive List in , Then work As a thread POP The operation takes the task out for execution .Redis It also provides operations List Of or relating to api, You can check directly , Delete except List The element of a paragraph in .

Redis Of list Is that every child element is String Double linked list of type , Can pass push and pop The operation starts at the head or tail of the list Add or remove elements , such List It can be used as a stack , It can also be used as a queue .