Add default value on a field while modifying existing elasticsearch mapping

Let's say I've an elasticsearch index with around 10M documents on it. Now I need to add a new filed with a default value e.g is_hotel_type=0 for each and every ES document. Later I'll update as per my requirments.

To do that I've modified myindex with a PUT request like below-

PUT myindex
{
  "mappings": {
    "rp": {
      "properties": {
        "is_hotel_type": {
          "type": "integer" 
        }
      }
    }
  }
}

Then run a painless script query with POST to update all the existing documents with the value is_hotel_type=0

POST myindex/_update_by_query
{
  "query": {
    "match_all": {}
  },
  "script" : "ctx._source.is_hotel_type = 0;"
}

But this process is very time consuming for a large index with 10M documents. Usually we can set default values on SQL while creating new columns. So my question- Is there any way in Elasticsearch so I can add a new field with a default value.I've tried below PUT request with null_value but it doesn't work for.

PUT myindex/_mapping/rp
{
  "properties": {
        "is_hotel_type": {
          "type": "integer",
           "null_value" : 0 
        }
      }
}

I just want to know is there any other way to do that without the script query?