HEXISTS
Syntax
        HEXISTS key field
- Available since:
- 2.0.0
- Time complexity:
- O(1)
- ACL categories:
- 
              
                @read,@hash,@fast,
Returns if field is an existing field in the hash stored at key.
Return
Integer reply, specifically:
- 1if the hash contains- field.
- 0if the hash does not contain- field, or- keydoes not exist.