What is redis index

#redis does not directly support indexing and needs to be maintained by yourself.

For non-range unique indexes, we can simply save the index as a KV pair, and v can save the main key. For range retrieval, or non-unique indexes, redis must be used zset to achieve. (Recommended learning: Redis video tutorial)

Give an example of a traditional user system

uid 用户id
name 用户名
credit 用户积分
type 类型

can be placed directly Retrieving

hmset usr:1 uid 1 name aaa credit 10 type 0
hmset usr:2 uid 2 name bbb credit 20 type 1

in a hashset by uid is very fast, but if you want to query users with type=1, you can only scan them all!

In a relational database, we can simply create an index on type

select * from usr where type=1

Such SQL can be executed efficiently. In redis, we need to maintain another zset

zadd usr.index.type 0 0:1
zadd usr.index.type 0 1:2

Note that all weights are set to 0, so that they can be retrieved directly by value, and then can be retrieved through

zrangebylex usr.index.type [1: (1;

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