[redis] list type

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List type

Redis Medium List The type and java Medium LinkedList similar , It can be regarded as a two-way linked list structure , It can support forward retrieval , Reverse retrieval is also supported .

characteristic ：

• Orderly
• Elements can be repeated
• Insert and delete fast
• The query speed is average

Often used to store an ordered data , for example ： Friends circle like 、 Comment list

The basic general commands are shown in the figure above , Here is a detailed introduction ！

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1.1 LPUSH & LPOP & RPUSH & RPOP

• LPUSH key element …: Insert one or more elements to the left of the list
• RPUSH key element …: Insert one or more elements to the right of the list

Add left 1、2、3, The actual order is 3、2、1; Add... To the right 4、5、6, The actual order is 4、5、6：

• LPOP key: Remove and return the first element to the left of the list , No return nil

• RPOP key: Remove and return the first element to the right of the list
  

Left side removal 3 Elements , Remove from the right 1 Elements , In the end 4、5 Two elements ：

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1.2 BLPOP & BRPOP

And LPOP、RPOP similar , Just wait for the specified time when there is no element , Not directly back nil（ Block access ）

As shown in the figure , We designate waiting user1 One hundred seconds , Add... In the new window user1 after , The original BLPOP The command has the result , And return the extracted element and the waiting time .

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1.3 LRANGE

Returns all elements within a range of subscripts ：

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