Redis Command Reference "EXPIRE"

EXPIRE

EXPIRE Key seconds

For a given key set time to Live, key 0 it will be automatically deleted when it expires (time to live).

In Redis, the time-to-live key is referred to as "volatile" (volatile).

The time to live can be removed by using the DEL command key , or by the SET and Getset commands (overwrite), which means that if a command simply modifies (alter) a value with a time-to-live key instead of a new key value Instead of it, the time to live is not changed.

For example, for an key execute INCR command, a lpush command on a list, or a hset command on a hash table, such operations do not modify key their own time-to-live.

On the other hand, if one is renamed with RENAME , the time to change is the key key same as before renaming.

Another possibility of the RENAME command is to attempt to rename a time-to-live with key another time-to-live another_key , when the old another_key (and its time-to-live) is deleted, and the old one is key renamed another_key , so the new is the same as the original key .

Use the PERSIST command to remove the time-to-live without deleting it key key , and to make it key a "persistent" (persistent) again key .

Update Time to Live

The newly specified time-to-live will replace the old time-to-live with an key execution EXPIRE command that already has a time-to-live.

Accuracy of expiration Time

In the Redis 2.4 release, the expiration time is delayed by 1 seconds-that is, even if key it has expired, it may be accessed within one second of expiration, and in the new Redis 2.6 release, the latency is reduced to 1 milliseconds.

What's different before Redis 2.1.3

In the previous version of Redis 2.1.3, modifying a time-to-live result in the key entire key deletion, which was made by the limitations of the then-duplicated (replication) layer, is now fixed.

Available versions:

>= 1.0.0

Complexity of Time:

O (1)

return value:

set to return successfully 1 . keyreturned if it does not exist or is unable to set the time-to- key live (for example, in Redis under 2.1.3, if you try to update key the lifetime) 0 .

Redis> set Cache_page "www.google.com" okredis> EXPIRE cache_page  # Set expiration time is 30 seconds (integer) 1redis> TTL Cach E_page    # View remaining time to Live (integer) 23redis> EXPIRE cache_page 30000   # Update expiration (integer) 1redis> TTL cache_page ( Integer) 29996

Mode: Navigation session

Suppose you have a Web service that intends to recommend items based on the N pages visited by the user recently, and assumes that the user has stopped viewing for more than 60 seconds, then clear the reading record (to reduce the amount of recommended calculations and keep the recommended items fresh).

These recently visited Page records, which we call "Navigation Sessions" (Navigation session), can be implemented in Redis with the INCR and Rpush commands: Whenever a user views a webpage, execute the following code:

MULTI    rpush pagewviews.user:<userid>/http/...    .. EXPIRE pagewviews.user:<userid> 60EXEC

If the user stops reading for more than 60 seconds, then its navigation session will be emptied, and when the user resumes viewing, the system will re-record the navigation session, continue to carry out the item recommendation.

Links: http://redisdoc.com/key/expire.html

Redis Command Reference "EXPIRE"