Sets the given keys to their respective values. MSETNX will not perform any operation at all even if just a single key already exists.
Because of this semantic MSETNX can be used in order to set different keys representing different fields of an unique logic object in a way that ensures that either all the fields or none at all are set.
MSETNX is atomic, so all given keys are set at once. It is not possible for clients to see that some of the keys were updated while others are unchanged.
Integer reply, specifically:
1if the all the keys were set.
0if no key was set (at least one key already existed).
(integer) 1redis> MSETNX key2 "there" key3 "world"
(integer) 0redis> MGET key1 key2 key3
1) "Hello" 2) "there" 3) (nil)