Glue crawler: exclude field or predefine it's type

I am getting json files to my s3. For example:

{
    "name" : "John",
    "lastname": "Doe",
    "meta" : {
        "x": "a",
        "y": "b",
        "unwanted_field": {
            "some": "stuff",
            "to": "ignore"
        }
    }
}

Is there a way exclude meta.unwanted_field key or predefine it's type as STRING during crawling process? Maybe somebody has a solution how I can achieve this without file reprocessing?

Thank you for any help.