HKEYS
Introduction and Use Case(s)
The HKEYS
command in Redis is used to retrieve all the keys (fields) in a hash stored at a specified key. This command is particularly useful when you need to inspect the structure of a hash or iterate over its fields for further processing.
Syntax
HKEYS key
Parameter Explanations
key
: The name of the hash from which to retrieve the fields. If the hash does not exist, an empty list is returned.
Return Values
The HKEYS
command returns a list of strings, each representing a field in the hash.
Example Outputs
- If the hash contains fields:
["field1", "field2", "field3"]
- If the hash is empty or does not exist:
[]
Code Examples
dragonfly> HSET myhash field1 "value1" field2 "value2"
(integer) 2
dragonfly> HKEYS myhash
1) "field1"
2) "field2"
dragonfly> HDEL myhash field1
(integer) 1
dragonfly> HKEYS myhash
1) "field2"
dragonfly> DEL myhash
(integer) 1
dragonfly> HKEYS myhash
(empty array)
Best Practices
- Ensure that the key exists and is of type hash before calling
HKEYS
to avoid unnecessary operations. - Combine
HKEYS
with other hash commands likeHGETALL
orHVALS
for more comprehensive data manipulations.
Common Mistakes
- Attempting to use
HKEYS
on a key that is not a hash will result in an error. Always verify the data type if unsure. - Forgetting to check if the hash is empty can lead to assumptions that the key doesn’t exist.
FAQs
What happens if the key does not exist?
If the specified key does not exist, HKEYS
returns an empty list.
Can I use HKEYS
on non-hash data types?
No, using HKEYS
on a key that holds a non-hash value results in an error.