Upsert data using painless script if updated_at is higher than previous document

I have a collection which gets updated frequently.

  1. We need to perform upsert operation, i.e., if document doesn't exist then create else update.
  2. Another constraint we require is timestamp of updated_at should be higher.

Please help. The query will be something like this. But I am getting error even after multiple try.

POST /test/_update/1
{
  "scripted_upsert": true,
  "script": {
    "source": """
      if ( ctx.op == 'create' ) {
        ctx._source.counter = params.count
      } else {
        ctx._source.counter += params.count
      }
    """,
    "params": {
      "updated_at": "2022-01-17T21:54:29.074Z"
    }
  },
  "upsert": {}
}```

Hi,

Is it a whole query? It looks there are no "count" field in "params".
What does the error message show?