XADD

XADD

Introduction and Use Case(s)

The XADD command in Redis is used to append a new entry to a stream. Streams are a type of data structure that allows for the storage of an ordered log of messages, making them particularly useful for messaging systems, event sourcing, and logging applications.

Syntax

XADD key ID field value [field value ...]

Parameter Explanations

key: The name of the stream.
ID: The unique identifier for the entry. It can be specified as * to let Redis generate a timestamp-based ID.
field value: Pairs of field names and values to store in the entry. At least one field-value pair must be provided.

Return Values

The command returns the ID of the added entry.

Example Outputs

When a new entry is added successfully:

dragonfly> XADD mystream * sensor-id 1234 temperature 19.8
"1633389163432-0"

Code Examples

dragonfly> XADD mystream * sensor-id 1234 temperature 19.8
"1633389163432-0"
dragonfly> XADD mystream 1633389163432-1 sensor-id 5678 temperature 22.5
"1633389163432-1"
dragonfly> XLEN mystream
(integer) 2
dragonfly> XRANGE mystream - +
1) 1) "1633389163432-0"
   2) 1) "sensor-id"
      2) "1234"
      3) "temperature"
      4) "19.8"
2) 1) "1633389163432-1"
   2) 1) "sensor-id"
      2) "5678"
      3) "temperature"
      4) "22.5"

Best Practices

Use meaningful IDs instead of relying on automatic generation, if the time sequence or specific ordering is critical.
Regularly trim your streams using the XTRIM command to maintain manageable sizes and performance.

Common Mistakes

Forgetting to provide at least one field-value pair will result in an error.
Using non-unique IDs can cause unexpected behavior, so ensure that IDs are unique if manually specified.

FAQs

What happens if I use the same ID for multiple entries?

Using the same ID for multiple entries can lead to overwriting or unexpected behavior. It’s best to ensure each ID is unique.

Can I have an empty stream?

No, streams require at least one entry. Attempting to create an empty stream will result in an error.