Determines whether a field exists in a hash.
HEXISTS key field
Returns if field is an existing field in the hash stored
at key.
One of the following:
Integer reply:
0 if the hash does not contain the field, or the key does
not exist.
Integer reply:
1 if the hash contains the field.
O(1)
@fast @hash @read
127.0.0.1:6379> HSET myhash field1 "foo"
(integer) 1
127.0.0.1:6379> HEXISTS myhash field1
(integer) 1
127.0.0.1:6379> HEXISTS myhash field2
(integer) 0HDEL, HEXPIRE, HEXPIREAT, HEXPIRETIME, HGET, HGETALL, HGETEX, HINCRBY, HINCRBYFLOAT, HKEYS, HLEN, HMGET, HMSET, HPERSIST, HPEXPIRE, HPEXPIREAT, HPEXPIRETIME, HPTTL, HRANDFIELD, HSCAN, HSET, HSETEX, HSETNX, HSTRLEN, HTTL, HVALS.