HSETEX

Introduction and Use Case(s)

HSETEX is a hypothetical command that combines the functionality of HSET and EXPIRE. It sets a field in the hash stored at a key, along with an expiration time for the entire hash. This command can be particularly useful when you need to ensure that hash entries automatically expire after a certain period.

Typical scenarios include caching user sessions, temporary data storage, and rate-limiting information where both the data needs to be set and its lifetime managed simultaneously.

Syntax

  1. HSETEX key field value seconds

Parameter Explanations

  • key: The name of the key holding the hash.
  • field: The field within the hash to set.
  • value: The value to associate with the field.
  • seconds: The expiration time in seconds for the hash.

Return Values

The return type for HSETEX would typically be an integer indicating if a new field was added or if an existing field was updated:

  • (integer) 1: If a new field is created.
  • (integer) 0: If the field already existed and was updated.

Code Examples

  1. dragonfly> HSETEX myhash field1 "value1" 60
  2. (integer) 1
  3. dragonfly> HSETEX myhash field2 "value2" 120
  4. (integer) 1
  5. dragonfly> HEXISTS myhash field1
  6. (integer) 1
  7. dragonfly> TTL myhash
  8. (integer) 60
  9. dragonfly> HSETEX myhash field1 "newvalue" 180
  10. (integer) 0
  11. dragonfly> TTL myhash
  12. (integer) 180

Best Practices

  • Use HSETEX for cache-related hashes where you want automatic cleanup without needing separate commands for setting expiration.

Common Mistakes

  • Setting different expirations for fields within the same hash won’t work as expected because the TTL applies to the entire hash, not individual fields.
  • Overwriting fields without considering the hash’s current TTL might lead to unexpected expiration behaviors.

FAQs

What happens to the TTL if I use HSETEX on an existing hash?

Using HSETEX on an existing hash with a new TTL will reset the TTL to the specified duration. This can affect all entries in the hash.

Can I use HSETEX to set multiple fields at once?

No, HSETEX operates on a single field at a time. To set multiple fields, you would need to call HSETEX multiple times or use a combination of HMSET and EXPIRE.