Redis一旦不被访问就失效（redis没有访问时失效）

Redis: Once Not Accessed, Expires

Redis is an open-source, in-memory data structure store that operates as a database, cache, and message broker. Redis stores data in KEY-value prs and supports several data structures such as strings, hashes, lists, sets, and sorted sets. It is known for its speed, simplicity, and ability to handle high throughput and low latency scenarios.

One of the interesting features of Redis is the ability to set an expiration time for a key-value pr. This means that once the key expires, Redis will automatically remove it from the database. This feature is useful in scenarios where the data stored in Redis has a limited lifespan or is expected to change frequently.

To set an expiration time for a key in Redis, you can use the `EXPIRE` command. The `EXPIRE` command takes two arguments: the key and the time in seconds after which the key will expire. For example, to set the key “foo” to expire after 60 seconds, you can use the following command:

redis> EXPIRE foo 60
(integer) 1

The `integer` value returned by the `EXPIRE` command indicates whether the key was found and the expiration time was set.

Once the key expires, Redis will automatically remove it from the database. If you try to access the expired key, Redis will return `nil`, indicating that the key does not exist. For example:

redis> GET foo
(nil)

You can also use the `TTL` command to check the remning time to live of a key. The `TTL` command takes one argument, the key, and returns the number of seconds remning before the key will expire. For example:

redis> TTL foo
(integer) 13

In this example, the TTL of the key “foo” is 13 seconds, which means that the key is set to expire in 13 seconds.

Redis also provides several other commands for controlling the expiration of keys, including `PERSIST`, which removes the expiration time from a key, and `PTTL`, which returns the remning time to live of a key in milliseconds.

Another interesting feature of Redis related to expiration is the ability to set an expiration time for a set of keys at once. This can be achieved using the `EXPIRE` command with the `*` wildcard. For example, to set an expiration time of 60 seconds for all keys starting with “foo:”, you can use the following command:

redis> EXPIRE foo:* 60
(integer) 2

The `integer` value returned by the `EXPIRE` command indicates the number of keys that were found and had their expiration time set.

In conclusion, Redis provides a convenient and powerful way to handle expiration of data stored in key-value prs. By setting an expiration time for a key, Redis ensures that the data is automatically removed from the database once it is no longer needed. This can help to free up memory and resources and improve the overall performance of Redis.

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