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Set processor

The set processor adds or updates fields in a document. It sets one field and associates it with the specified value. If the field already exists, then its value is replaced with the provided one unless the override parameter is set to false. When override is false and the specified field exists and isn’t null, the value of the field remains unchanged. A field whose value is null is always overwritten.

The following is the syntax for the set processor:

{
  "description": "...",
  "processors": [
    {
      "set": {
        "field": "new_field",
        "value": "some_value"
      }
    }
  ]
}

Configuration parameters

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

Parameter Required/Optional Description
field Required The name of the field to be set or updated. Supports template snippets.
value Required The value assigned to the field. Supports template snippets.
override Optional A Boolean flag that determines whether the processor should override the existing value of the field. Default is true.
ignore_empty_value Optional A Boolean flag that determines whether the processor should ignore null values or empty strings. Default is false.
description Optional A description of the processor’s purpose or configuration.
if Optional Specifies to conditionally execute the processor.
ignore_failure Optional Specifies to ignore processor failures. See Handling pipeline failures.
on_failure Optional Specifies a list of processors to run if the processor fails during execution. These processors are executed in the order they are specified.
tag Optional An identifier tag for the processor. Useful for debugging in order to distinguish between processors of the same type. For more information, see Using processor tags for monitoring and debugging.

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 set-pipeline that uses the set processor to add a new field new_field with the value some_value to the document:

PUT _ingest/pipeline/set-pipeline
{
  "description": "Adds a new field 'new_field' with the value 'some_value'",
  "processors": [
    {
      "set": {
        "field": "new_field",
        "value": "some_value"
      }
    }
  ]
}

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/set-pipeline/_simulate
{
  "docs": [
    {
      "_source": {
        "existing_field": "value"
      }
    }
  ]
}

Response

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

{
  "docs": [
    {
      "doc": {
        "_index": "_index",
        "_id": "_id",
        "_source": {
          "existing_field": "value",
          "new_field": "some_value"
        },
        "_ingest": {
          "timestamp": "2024-05-30T21:56:15.066180712Z"
        }
      }
    }
  ]
}

Step 3: Ingest a document

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

POST testindex1/_doc?pipeline=set-pipeline
{
  "existing_field": "value"
}

Response

The request indexes the document into the testindex1 index with the new_field field set to some_value, as shown in the following response:

{
  "_index": "testindex1",
  "_id": "1",
  "_version": 1,
  "result": "created",
  "_shards": {
    "total": 2,
    "successful": 1,
    "failed": 0
  },
  "_seq_no": 0,
  "_primary_term": 1
}

Step 4 (Optional): Retrieve the document

To retrieve the document, run the following query:

GET testindex1/_doc/1

Copying a value from another field

To copy a value from one field to another, reference the source field in value using a template snippet. The following request copies the value of the customer.address.city field to the shipping.city field:

POST _ingest/pipeline/_simulate
{
  "pipeline": {
    "processors": [
      {
        "set": {
          "field": "shipping.city",
          "value": "{{{customer.address.city}}}"
        }
      }
    ]
  },
  "docs": [
    {
      "_source": {
        "customer": {
          "address": {
            "city": "Portland"
          }
        }
      }
    }
  ]
}

The response shows that the shipping.city field contains the copied value:

{
  "docs": [
    {
      "doc": {
        "_index": "_index",
        "_id": "_id",
        "_source": {
          "shipping": {
            "city": "Portland"
          },
          "customer": {
            "address": {
              "city": "Portland"
            }
          }
        },
        "_ingest": {
          "timestamp": "2026-10-14T19:44:03.269176256Z"
        }
      }
    }
  ]
}

Template snippets always produce a string. For example, copying a numeric field value of 24.99 produces the string "24.99". To copy a value while preserving its type, or to copy an entire object, use the copy processor.

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