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You're viewing version 2.9 of the OpenSearch documentation. This version is no longer maintained. For the latest version, see the current documentation. For information about OpenSearch version maintenance, see Release Schedule and Maintenance Policy.

Append

The append processor is used to add values to a field:

  • If the field is an array, the append processor appends the specified values to that array.
  • If the field is a scalar field, the append processor converts it to an array and appends the specified values to that array.
  • If the field does not exist, the append processor creates an array with the specified values.

The following is the syntax for the append processor:

{
  "append": {
    "field": "your_target_field",
    "value": ["your_appended_value"]
  }
}

Configuration parameters

The following table lists the required and optional parameters for the append processor.

Parameter Required Description
field Required The name of the field to which the data should be appended. Supports template snippets.
value Required The value to be appended. This can be a static value or a dynamic value derived from existing fields. Supports template snippets.
description Optional A brief description of the processor.
if Optional A condition for running this processor.
ignore_failure Optional If set to true, failures are ignored. Default is false.
on_failure Optional A list of processors to run if the processor fails.
tag Optional An identifier tag for the processor. Useful for debugging to distinguish between processors of the same type.

Using the processor

Follow these steps to use the processor in a pipeline.

Step 1: Create a pipeline.

The following query creates a pipeline, named user-behavior, that has one append processor. It appends the page_view of each new document ingested into OpenSearch to an array field named event_types:

PUT _ingest/pipeline/user-behavior
{
  "description": "Pipeline that appends event type",
  "processors": [
    {
      "append": {
        "field": "event_types",
        "value": ["page_view"]
      }
    }
  ]
}

Step 2 (Optional): Test the pipeline.

It is recommended that you test your pipeline before you ingest documents.

To test the pipeline, run the following query:

POST _ingest/pipeline/user-behavior/_simulate
{
  "docs":[
    {
      "_source":{
      }
    }
  ]
}

Response

The following response confirms that the pipeline is working as expected:

{
  "docs": [
    {
      "doc": {
        "_index": "_index",
        "_id": "_id",
        "_source": {
          "event_types": [
            "page_view"
          ]
        },
        "_ingest": {
          "timestamp": "2023-08-28T16:55:10.621805166Z"
        }
      }
    }
  ]
}

Step 3: Ingest a document.

The following query ingests a document into an index named testindex1:

PUT testindex1/_doc/1?pipeline=user-behavior
{
}

Step 4 (Optional): Retrieve the document.

To retrieve the document, run the following query:

GET testindex1/_doc/1

Because the document does not contain an event_types field, an array field is created and the event is appended to the array:

{
  "_index": "testindex1",
  "_id": "1",
  "_version": 2,
  "_seq_no": 1,
  "_primary_term": 1,
  "found": true,
  "_source": {
    "event_types": [
      "page_view"
    ]
  }
}
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