# Using an existing JSON document from a field

![Elasticsearch REST Bulk Insert step, Document tab - Use existing option](/files/5StKL6uRLaYVOz3Qq3XA)

Choose the **Use an existing JSON document from a field** option if the document that you want to index is already in a JSON form in a field on the input stream.

| Field          | Description                                                                                              |
| -------------- | -------------------------------------------------------------------------------------------------------- |
| **JSON Field** | Select the name of the incoming field that contains a JSON document to be indexed for each row of input. |


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.pentaho.com/pdia-data-integration/10.2-data-integration/pdi-transformation-steps-reference-overview/elasticsearch-rest-bulk-insert/options-elasticsearch-rest-bulk-insert/document-tab-elasticsearch-rest-bulk-insert/using-an-existing-json-document-from-a-field-elasticsearch-rest-bulk-insert.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.