opensearch-docs-cn/_api-reference/ingest-apis/processors/append.md

layout	title	parent	grand_parent	nav_order
default	Append	Ingest processors	Ingest APIs	10

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"]
  }
}

{% include copy-curl.html %}

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"]
      }
    }
  ]
}

{% include copy-curl.html %}

Step 2 (Optional): Test the pipeline.

It is recommended that you test your pipeline before you ingest documents. {: .tip}

To test the pipeline, run the following query:

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

{% include copy-curl.html %}

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
{
}

{% include copy-curl.html %}

Step 4 (Optional): Retrieve the document.

To retrieve the document, run the following query:

GET testindex1/_doc/1

{% include copy-curl.html %}

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"
    ]
  }
}