JSON.OBJLEN

Introduction and Use Case(s)

The JSON.OBJLEN command in Redis is used to get the number of keys in a JSON object stored at a specified path. It is part of the RedisJSON module, which allows you to manipulate JSON data directly within Redis. This command is particularly useful for quickly retrieving the size of a JSON object without needing to fetch and parse the entire object.

Syntax

  1. JSON.OBJLEN <key> [path]

Parameter Explanations

  • <key>: The key under which the JSON document is stored.
  • [path]: (Optional) The path to the JSON object whose length is to be retrieved. Defaults to the root if not specified.

Return Values

The command returns an integer representing the number of keys in the specified JSON object.

Example Outputs

  • If the JSON object has 3 keys, the output will be:

    1. (integer) 3

  • If the specified path does not point to a JSON object, the output will be:

    1. (nil)

Code Examples

  1. dragonfly> JSON.SET myjson $ '{"name":"John","age":30,"city":"New York"}'
  2. OK
  3. dragonfly> JSON.OBJLEN myjson $
  4. (integer) 3
  5. dragonfly> JSON.SET myjson $ '{"person":{"name":"John","age":30},"city":"New York"}'
  6. OK
  7. dragonfly> JSON.OBJLEN myjson $.person
  8. (integer) 2
  9. dragonfly> JSON.OBJLEN myjson $.city
  10. (nil)

Best Practices

  • Always ensure that the path provided points to a valid JSON object. Using a path that points to a non-object type (e.g., string, array) will result in a nil response.
  • Combine JSON.OBJLEN with other JSON commands to efficiently manage and query your JSON data within Redis.

Common Mistakes

  • Providing an incorrect path that does not lead to a JSON object can cause confusion. Double-check paths to ensure they are correct.
  • Assuming that the command will work on non-object types like arrays or strings. The JSON.OBJLEN command is specifically designed for objects.

FAQs

What happens if I provide a non-existent key?

If you provide a key that does not exist, the result will be (nil).

Can I use JSON.OBJLEN on JSON arrays or strings?

No, JSON.OBJLEN is specifically for counting the keys in a JSON object. It will return (nil) if used on other types like arrays or strings.