Document the usage of update document API with ingest pipeline

_api-reference/document-apis/update-document.md

@@ -14,6 +14,14 @@ redirect_from:
 If you need to update a document's fields in your index, you can use the update document API operation. You can do so by specifying the new data you want to be in your index or by including a script in your request body, which OpenSearch runs to update the document. By default, the update operation only updates a document that exists in the index. If a document does not exist, the API returns an error. To _upsert_ a document (update the document that exists or index a new one), use the [upsert](#using-the-upsert-operation) operation.
 
 
+You cannot explicitly specify an ingest pipeline when calling the Update Document API. If a `default_pipeline` or `final_pipeline` is defined in your index, the following behavior applies:
+
+- **Upsert operations**: When indexing a new document, the `default_pipeline` and `final_pipeline` defined in the index are executed as specified.  
+- **Update operations**: When updating an existing document, ingest pipeline execution is not recommended because it may produce erroneous results. Support for running ingest pipelines during update operations is deprecated and will be removed in version 3.0.0. If your index has a defined ingest pipeline, the update document operation will return the following deprecation warning: 
+```
+the index [sample-index1] has a default ingest pipeline or a final ingest pipeline, the support of the ingest pipelines for update operation causes unexpected result and will be removed in 3.0.0
+```
+
 ## Path and HTTP methods
 
 ```json