append.md

applies_to
serverless stack ga preview =9.1, ga 9.2+

Append processor [streams-append-processor]

% Need use cases

Use the Append processor to add a value to an existing array field, or create the field as an array if it doesn’t exist.

To use an append processor:

1. Select Create → Create processor.
2. Select Append from the Processor menu.
3. Set Source Field to the field you want append values to.
4. Set Target field to the values you want to append to the Source Field.

This functionality uses the {{es}} append processor internally, but you configure it in Streamlang. Streamlang doesn’t always have 1:1 parity with the ingest processor options and behavior. Refer to Processor limitations and inconsistencies.