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This article mainly introduces the method of redis data deletion, which is very detailed and has a certain reference value. Friends who are interested must finish reading it!

There are three common deletion strategies for Redis:

1. Passive deletion (lazy deletion): when reading / writing an expired Key, the lazy delete policy is triggered and the Key is deleted directly

two。 Proactive deletion (regular deletion): Redis conducts regular inspections to clean up expired Key

3. When the memory reaches the maxmemory configuration, the deletion of Key will be triggered.

Active deletion

In Redis, general operations are implemented by redis.c/serverCron, which mainly performs the following operations:

1. Update all kinds of statistics of the server, such as time, memory footprint, database footprint, etc.

two。 Clean up expired key-value pairs in the database.

3. Resize unreasonable databases.

4. Close and clean up clients with failed connections.

5. Try an AOF or RDB persistence operation.

6. If the server is the primary node, periodically synchronize the subsidiary nodes.

If you are in cluster mode, perform regular synchronization and connectivity tests on the cluster.

Redis runs serverCron as a time event, ensuring that it runs automatically at regular intervals, and because serverCron needs to run periodically while the Redis server is running, it is a cyclical time event: serverCron executes periodically until the server shuts down.

Summary

If a large number of Key expires every day in Redis (for example, tens of millions), then you must consider cleaning up the expired Key:

Increase the frequency of Redis active cleanup (by increasing the hz parameter)

The easiest way to manually clean up expired Key is to perform scan operation. The scan operation will trigger the first passive deletion. Do not forget to add count during scan operation.

The number of Key returned by the dbsize command, including expired Key

The Key returned by the randomkey command, excluding expired Key

The Key returned by the scan command, including expired Key

# Keyspace returned by the info command

Db6:keys=1034937352,expires=994731489,avg_ttl=507838502

The number of Key corresponding to keys is equal to that of dbsize

Expires refers to the number of Key with expiration time set

Avg_ttl refers to the average expiration time of a Key with an expiration time set (in milliseconds)

The above are all the contents of the method of deleting data by redis. Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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