join.md

applies_to	serverless stack ga ga 9.4+
products	id observability id elasticsearch id kibana id cloud-serverless id cloud-hosted id cloud-enterprise id cloud-kubernetes id elastic-stack
description	Concatenate values from multiple fields into a single field using a delimiter with the Streams join processor in Streamlang.

Join processor [streams-join-processor]

The Join processor concatenates the values of multiple fields into a single field with a delimiter between them.

To join fields:

1. Select Create → Create processor.
2. Select Join from the Processor menu.
3. Set the Source Fields to the fields you want to join.
4. Set the Delimiter to the separator placed between values.
5. Set the Target field where the joined result is stored.

YAML reference [streams-join-yaml-reference]

In YAML mode, configure the join processor using the following parameters. For the complete Streamlang syntax, refer to the Streamlang reference.

Parameter	Type	Required	Description
from	string[]	Yes	Source fields to join.
delimiter	string	Yes	Delimiter placed between values.
to	string	Yes	Target field.
ignore_missing	boolean	No	When true, skip this processor if any source field is missing.

- action: join
  from:
    - attributes.last_name
    - attributes.first_name
  delimiter: ","
  to: attributes.full_name