It returns an error when
key does not exist.
newkey already exists it is overwritten, when this happens RENAME executes an implicit DEL operation, so if the deleted key contains a very big value it may cause high latency even if RENAME itself is usually a constant-time operation.
In Cluster mode, both
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.
<= 3.2.0: Before Redis 3.2.0, an error is returned if source and destination names are the same.
"OK"redis> RENAME mykey myotherkey
"OK"redis> GET myotherkey