Is your feature request related to a problem? Please describe

The rename ingest processor always throws error when the target field exists in the document, which is not friendly:

POST _ingest/pipeline/_simulate
{
  "pipeline": {
    "processors": [
      {
        "rename": {
          "field": "a",
          "target_field": "b"
        }
      }
    ]
  },
  "docs": [
    {
      "_source": {
        "a":1,
        "b":2
      }
    }
  ]
}

, response:

{
  "docs": [
    {
      "error": {
        "root_cause": [
          {
            "type": "illegal_argument_exception",
            "reason": "field [b] already exists"
          }
        ],
        "type": "illegal_argument_exception",
        "reason": "field [b] already exists"
      }
    }
  ]
}

. Just like the Hard_rename rule in the Modify filter plugin of fluent-bit, the rename ingest processor can support something like override_target, which can be used to override the target field if it does exist.

Describe the solution you'd like

Rename ingest processor supports overriding target field if exists.

Related component

Indexing

Describe alternatives you've considered

No response

Additional context

No response