Renames key to newkey if newkey does not yet exist.
It returns an error when key does not exist.
In Cluster mode, both key and newkey must be in the same hash slot, meaning that in practice only keys that have the same hash tag can be reliably renamed in cluster.
*History
<= 3.2.0: Before Redis 3.2.0, an error is returned if source and destination names are the same.
*Return value
Integer reply, specifically:
1ifkeywas renamed tonewkey.0ifnewkeyalready exists.
*Examples
redis>
SET mykey "Hello"
"OK"redis> SET myotherkey "World"
"OK"redis> RENAMENX mykey myotherkey
(integer) 0redis> GET myotherkey
"World"