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Lowercase

The lowercase processor converts all the text in a specific field to lowercase letters. The following is the syntax for the lowercase processor:

{
  "lowercase": {
    "field": "field_name"
  }
}

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Configuration parameters

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

Name	Required	Description
`field`	Required	The name of the field that contains the data to be converted. 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.
`ignore_missing`	Optional	Specifies whether the processor should ignore documents that do not have the specified field. Default is `false`.
`tag`	Optional	An identifier tag for the processor. Useful for debugging to distinguish between processors of the same type.
`target_field`	Optional	The name of the field in which to store the parsed data. Default is `field`. By default, `field` is updated in place.

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 lowercase-title, that uses the lowercase processor to lowercase the title field of a document:

PUT _ingest/pipeline/lowercase-title
{
  "description" : "Pipeline that lowercases the title field",
  "processors" : [
    {
      "lowercase" : {
        "field" : "title"
      }
    }
  ]
}

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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/lowercase-title/_simulate
{
  "docs": [
    {
      "_index": "testindex1",
      "_id": "1",
      "_source": {
        "title": "WAR AND PEACE"
      }
    }
  ]
}

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Response

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

{
  "docs": [
    {
      "doc": {
        "_index": "testindex1",
        "_id": "1",
        "_source": {
          "title": "war and peace"
        },
        "_ingest": {
          "timestamp": "2023-08-22T17:39:39.872671834Z"
        }
      }
    }
  ]
}

Step 3: Ingest a document.

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

PUT testindex1/_doc/1?pipeline=lowercase-title
{
  "title": "WAR AND PEACE"
}

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Step 4 (Optional): Retrieve the document.

To retrieve the document, run the following query:

GET testindex1/_doc/1

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