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redis GETSET command syntax

Function: Set the value of the given key to value and return the old value of key. When key exists but is not of type string, an error is returned.

Syntax: GETSET key value

Available versions:>= 1.0.0

Time complexity : O(1)

Return: Return the old value of the given key. When key has no old value, that is, when key does not exist, nil is returned.

redis GETSET command example

redis> GETSET db mongodb    # 没有旧值,返回 nil
(nil)
redis> GET db
"mongodb"
redis> GETSET db redis      # 返回旧值 mongodb
"mongodb"
redis> GET db
"redis"