HSET

Introduction and Use Case(s)

The HSET command in Redis is used to set the value of a field in a hash. If the hash does not exist, it is created. This command is typically used for storing objects or records where each field represents an attribute of the object.

Syntax

  1. HSET key field value [field value ...]

Parameter Explanations

  • key: The name of the hash.
  • field: The field within the hash whose value you want to set.
  • value: The value to assign to the field.

Multiple field-value pairs can be specified in a single HSET command.

Return Values

The command returns an integer representing the number of fields that were added to the hash, not including fields that already existed.

  • If a new field is added: (integer) 1
  • If an existing field’s value is updated: (integer) 0

Code Examples

  1. dragonfly> HSET myhash field1 "value1"
  2. (integer) 1
  3. dragonfly> HSET myhash field2 "value2"
  4. (integer) 1
  5. dragonfly> HSET myhash field2 "new_value2"
  6. (integer) 0
  7. dragonfly> HGETALL myhash
  8. 1) "field1"
  9. 2) "value1"
  10. 3) "field2"
  11. 4) "new_value2"

Best Practices

  • Use meaningful and consistent naming conventions for keys and fields to keep data organized and understandable.
  • Consider using TTL (EXPIRE) for hashes if the data should only persist for a specific period.

Common Mistakes

  • Not checking if a field already exists before setting a value might lead to unintended data overwrites.
  • Passing incorrect types for field or value can cause unexpected behavior.

FAQs

What happens if I HSET a value to a non-existing hash?

A new hash will be created automatically with the specified field-value pair.

Can HSET handle multiple fields at once?

Yes, you can set multiple field-value pairs by chaining them in the command.

Will HSET overwrite existing fields?

Yes, if the field already exists, its value will be overwritten.