prepareAndExecute with UPSERT not working

[Plamen Paskov]

Hey folks,
I'm trying to UPSERT some data via the json api but no luck for now. My 
requests looks like:

{
  "request": "openConnection",
  "connectionId": "6"
}

{
  "request": "createStatement",
  "connectionId": "6"
}

{
  "request": "prepareAndExecute",
  "connectionId": "6",
  "statementId": 9,
  "sql": "UPSERT INTO us_population VALUES('IL','Chicago',10000000)",
  "maxRowCount": -1
}

The response for prepareAndExecute looks like the operation is 
successful but i don't see the new data added to the table.

{
  "response": "executeResults",
  "missingStatement": false,
  "rpcMetadata": {
    "response": "rpcMetadata",
    "serverAddress": "ip-172-31-27-198:8765"
  },
  "results": [
    {
      "response": "resultSet",
      "connectionId": "6",
      "statementId": 9,
      "ownStatement": false,
      "signature": null,
      "firstFrame": null,
      "updateCount": 1,
      "rpcMetadata": {
        "response": "rpcMetadata",
        "serverAddress": "ip-172-31-27-198:8765"
      }
    }
  ]
}

Any ideas?
Thanks in advance!