RMap.putIfAbsent optimization

src/main/java/org/redisson/RedissonMap.java

@@ -194,8 +194,7 @@ public class RedissonMap<K, V> extends RedissonExpirable implements RMap<K, V> {
     @Override
     public Future<V> putIfAbsentAsync(K key, V value) {
         return commandExecutor.evalWriteAsync(getName(), codec, EVAL_PUT,
-                "if redis.call('hexists', KEYS[1], ARGV[1]) == 0 then "
-                    + "redis.call('hset', KEYS[1], ARGV[1], ARGV[2]); "
+                 "if redis.call('hsetnx', KEYS[1], ARGV[1], ARGV[2]) == 1 then "
                     + "return nil "
                 + "else "
                     + "return redis.call('hget', KEYS[1], ARGV[1]) "