[Feature Request] Rename ingest processor supports overriding target field if exists

[gaobinlong]

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

[peternied]

[Triage - attendees 1 2 3 4 5]
@gaobinlong Thanks for filing this issue, please create a pull request to add this functionality.

Note; it sounds like this scenario might be better served with a new processor named 'move'

[gaobinlong]

[Triage - attendees 1 2 3 4 5] @gaobinlong Thanks for filing this issue, please create a pull request to add this functionality.

Note; it sounds like this scenario might be better served with a new processor named 'move'

Thank you, I've created a PR for this issue, and I think move processor could do more things than the rename processor such as move multiple fields to an object field(just like move multiple files to a directory in Linux), will dive deep into it.

[gaobinlong]

Closed by #12990.