XLEN

Introduction and Use Case(s)

XLEN is a Redis command used to get the length of a stream. This command is particularly useful in scenarios where you need to monitor the size of the stream, implement logic based on the number of entries, or perform housekeeping tasks.

Syntax

  1. XLEN key

Parameter Explanations

  • key: The name of the stream for which you want to obtain the length. This is a required parameter and must be a valid stream key.

Return Values

XLEN returns the number of entries in the stream. If the stream does not exist, it returns 0.

Example Output:

  • When the stream has entries: (integer) 5
  • When the stream does not exist: (integer) 0

Code Examples

  1. dragonfly> XADD mystream * field1 value1 field2 value2
  2. "1684749275426-0"
  3. dragonfly> XADD mystream * field1 value3 field2 value4
  4. "1684749281234-0"
  5. dragonfly> XLEN mystream
  6. (integer) 2
  7. dragonfly> XLEN nonexistingstream
  8. (integer) 0

Best Practices

  • Regularly monitor the length of streams to keep track of data growth and manage resources effectively.
  • Implement checks using XLEN to trigger actions when a stream exceeds a certain size.

Common Mistakes

  • Using XLEN on a key that is not a stream will result in an error. Always ensure the key is associated with a stream data type.

FAQs

What happens if I use XLEN on a key that is not a stream?

You will receive an error message indicating that the key is not a stream type. Make sure to validate the key’s data type before using XLEN.

Can XLEN return a negative value?

No, XLEN will always return a non-negative integer. If the stream does not exist, it returns 0.