删除 hashmap 中的所有 key.
name
The number of key deleted in that hashmap.
ssdb 127.0.0.1:8888> hset h k v ok (0.000 sec) ssdb 127.0.0.1:8888> hclear h 1 (0.000 sec) ssdb 127.0.0.1:8888> hclear h 0 (0.000 sec) ssdb 127.0.0.1:8888>