Redis (VI) - list of common data types of redis

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brief introduction

Redis The list in is a simple list of strings , You can add an element to the head of the list （ On the left ） Or tail （ On the right ）, You can use it to make a microblog timeline list , It can also act as a queue

Common commands

1. From the left / Insert one or more values... To the right

# Insert... From the left 
lpush <key1> <value1>  <value2> ......
# Insert... From the right 
rpush <key1> <value1>  <value2> ......

2. From the left / Spit out a value on the right , Take out a value and delete it , Value at key at , Value dead key dead .

# Spit it out on the left 
lpop <key1>
# Spit it out from the right 
rpop <key1>

As can be seen from the above examples , Insert from the left and spit out from the left , That is the form of first in and last out , If you insert from the left and spit out from the right, that's the form of first in first out .

3. from <key1> Spit a value on the right side of the list , insert <key2> To the left of the list

rpoplpush <key1> <key2>

4. Get elements according to index subscript （ From left to right ）, among <start> by 0 Time refers to the first one on the left , <stop> by -1 Time refers to the first one on the right ,（0~-1 To get all ）

lrange <key> <start> <stop>

6. Get elements according to index subscript （ From left to right ）

lindex <key> <index>

7. Get the list length

llen <key>

9. stay <value> In front of | Insert... At the back <newvalue> Insert value

# stay `<value>`  Insert in front of `<newvalue>`  Insert value 
linsert <key> before <value> <newvalue>
#`<value>`  Insert after `<newvalue>`  Insert value 
linsert <key> after <value> <newvalue>

10. from <value> Delete... On the left of n individual <value>（ From left to right ）

lrem <key1> <n> <value>

12. Will list <key> Subscript to be <index> Replace the value of with <value>

lset <key> <index> <value>

data structure

List The data structure of is fast linked list quickList.
In the case of fewer list elements, use a continuous memory storage , This structure is ziplist, That is, compress the list .
It stores all the elements next to each other , Allocated is a continuous block of memory .
When there is a large amount of data, it will be changed to quickList.
Because ordinary linked list needs too much additional pointer space , It's a waste of space , For example, what is stored in this list is int Type data , Structure Shanghai requires two additional pointers prev and next.

Redis Linking lists and ziplist Combined to form quicklist. That is to say, multiple ziplist Use two-way pointer string to use . This not only satisfies the fast insertion and deletion performance , There will not be too much space redundancy .
For details, you can learn about this article Redis（ 7、 ... and ）-Redis Of list The data structure of the list - Quick list

Reference resources

《Redis Design and implementation 》
Redis Basic types and their data structures