Retrieving a copy_to field in Elasticsearch (Kibana syntax)

kibana.json

DELETE my_index
PUT my_index
{
  "settings": {
    "number_of_shards": 1
  }, 
  "mappings": {
    "_doc": {
      "properties": {
        "first_name": {
          "type": "text",
          "copy_to": "full_name" 
        },
        "last_name": {
          "type": "text",
          "copy_to": "full_name" 
        },
        "full_name": {
          "type": "text",
          "store": true
        }
      }
    }
  }
}

PUT my_index/_doc/1
{
  "first_name": "John",
  "last_name": "Smith"
}
GET my_index/_search
{
  "stored_fields": [ "first_name", "full_name" ]
}

GET my_index/_doc/1/_termvectors
{
  "fields" : ["last_name", "full_name"]
}