JSON.STRLEN

The JSON.STRLEN command is used to determine the length of a JSON string at a specified path within a JSON document stored in DiceDB.

Syntax

JSON.STRLEN <key> <path>

Parameters

Parameter	Description	Type	Required
key	The key under which the JSON document is stored.	String	Yes
path	The JSONPath to the string within the JSON document. The path must contain a string.	String	No

Return Value

Condition	Return Value
JSON string is found at the specified path	Length of the JSON string.
JSONPath contains * wildcard	Indicates the length of each key in the JSON. Returns nil for non-string keys.

Behaviour

When the JSON.STRLEN command is executed, DiceDB will:

1. If the specified key does not exist, the command returns (nil).
2. If path is not specified, the command takes $ as root path and if the data at root path is string, returns an integer that represents the length of the string and if the data at root is not a string, returns an error indicating a type mismatch.
3. $ is considered as root path which returns the length of the string if the data at root path is of type string or returns nil if the data at root is not of type string.
4. If the specified path exists and points to a JSON string, the command returns the length of the string.
5. Multiple results are represented as a list in case of wildcards(*), where each string length is returned in order of appearance and nil is returned if it’s not a string.

Errors

The following errors may be raised when executing the JSON.STRLEN command:

1. Incorrect Number of Arguments:
   • (error) ERROR wrong number of arguments for 'JSON.STRLEN' command
   • This error occurs if the number of arguments provided to the command is incorrect.
2. Invalid JSONPath:
   • (error) ERROR invalid JSONPath
   • This error occurs if the specified path does not exist within the JSON document.
3. Wrong Type Error:
   • (error) WRONGTYPE wrong type of path value - expected string but found {DataType at root path}
   • This error occurs when a valid key is provided but no specific path value is given. By default, DiceDB assumes the root path ($) in such cases. If the data at the root path is not of type string, this error is returned, indicating a type mismatch between the expected string and the actual data type at the root.

Example Usage

Basic Usage

Assume we have a JSON document stored under the key user:1001:

{
  "name": "John Doe",
  "email": "john.doe@example.com",
  "address": {
    "city": "New York",
    "zipcode": "10001"
  }
}

To get the length of the name string:

JSON.STRLEN user:1001 $.name
(integer) 8

Nested JSON String

To get the length of the city string within the address object:

JSON.STRLEN user:1001 $.address.city
(integer) 8

Non-Existent Path

If the path does not exist:

JSON.STRLEN user:1001 $.phone
(empty array)

Path is Not a String

If the path points to a non-string value:

JSON.STRLEN user:1001 $.address
(nil)

Notes

• JSONPath expressions are used to navigate within the JSON document. Ensure that the path provided is valid and points to a JSON string to avoid errors.

By following this documentation, users should be able to effectively utilize the JSON.STRLEN command to determine the length of JSON strings stored within their DiceDB database.