What is Redis? What are the application scenarios?

This article brings you what is Redis? What are the application scenarios? It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

1. Introduction to Redis

Redis is an open source key-value single-threaded database that supports string, list, set, zset and hash type data.

Default port: 6379

Default number of databases: 16

2. Advantages:

1.nosql database has no correlation, simple data structure, and expansion Tables are easier

2.nosql has fast reading speed and fast processing of larger data

3. Applicable scenarios:

1 .Highly concurrent reading and writing of data

2. Reading and writing of massive data

Data with high scalability requirements

4. Uncomfortable scenarios:

1. Require transaction support (non-relational database)

2. Based on sql structured query storage, complex relationships

5 , Application scenarios

The following authors are Redis author @antirez. He describes some application scenarios that Redis is more suitable for. NoSQLFan briefly lists them here for everyone to have an overview:

1. Operation of fetching the latest N data

For example, typically fetching the latest articles on your website, through the following method, we can put the IDs of the latest 5000 comments in the Redis List collection, and Get the part beyond the collection from the database

• Use the LPUSH latest.commentseddfa97ffc1dc71769e3f42e462dfe8e command to insert data into the list collection

• ##After the insertion is completed, use the LTRIM latest.comments 0 5000 command to always save only the latest 5000 IDs

• Then we can use the following when getting comments on a certain page on the client Logic (pseudocode)

FUNCTION get_latest_comments(start,num_items):
    id_list = redis.lrange("latest.comments",start,start+num_items-1)
    IF id_list.length < num_items
        id_list = SQL_DB("SELECT ... ORDER BY time LIMIT ...")
    END
    RETURN id_list
END

If you have different filtering dimensions, such as the latest N items of a certain category, then you can create another List based on this category and only store the ID If so, Redis is very efficient.

2.

Ranking application, take TOP N operations

The difference between this requirement and the above requirement is that the previous operation uses time as the weight, and this one uses a certain The first condition is weight, such as sorting by the number of likes. At this time, our

sorted set needs to be used. Set the value you want to sort to the score of the sorted set, and set the specific data to the corresponding value, you only need to execute one ZADD command each time.

3. Applications that need to accurately set the expiration time

For example, you can set the score value of the sorted set mentioned above to the timestamp of the expiration time, then You can simply sort by the expiration time and clear the expired data regularly. Not only does it clear the expired data in Redis, you can completely regard the expiration time in Redis as an index of the data in the database, and use Redis to find out which data is needed. Delete upon expiration, and then accurately delete the corresponding records from the database.

4.

Counter application

Redis commands are all atomic. You can easily use INCR and DECR commands to build a counter system.

5.Uniq operation to obtain all data deduplication values ​​for a certain period of time

This is the most suitable to use the set data structure of Redis. You only need to keep throwing data into the set. set means collection, so it will be automatically deduplicated.

6. Real-time system,

anti-spam system

Through the set function mentioned above, you can know whether an end user has performed a certain operation, and you can find its Collection of operations and analysis, statistical comparison, etc. Nothing is impossible, only unimaginable.

7.Pub/Sub builds a real-time messaging system

Redis’ Pub/Sub system can build a real-time messaging system, such as many examples of real-time chat systems built with Pub/Sub.

8. Build a

queue system

Use list to build a queue system, use sorted set to even build a

priority queue system.

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