joinで子供をハイライト

sample.json

PUT join_highlight
{
  "mappings": {
    "properties": {
      "my_id": {
        "type": "keyword"
      },
      "my_join_field": { 
        "type": "join",
        "relations": {
          "question": "answer" 
        }
      }
    }
  }
}

PUT join_highlight/_doc/1?refresh
{
  "my_id": "1",
  "text": "This is a question",
  "my_join_field": {
    "name": "question" 
  }
}

PUT join_highlight/_doc/2?refresh
{
  "my_id": "2",
  "text": "This is another question",
  "my_join_field": {
    "name": "question"
  }
}

PUT join_highlight/_doc/3?routing=1&refresh
{
  "my_id": "3",
  "text": "This is an answer",
  "my_join_field": {
    "name": "answer", 
    "parent": "1" 
  }
}

PUT join_highlight/_doc/4?routing=1&refresh
{
  "my_id": "4",
  "text": "This is another answer",
  "my_join_field": {
    "name": "answer",
    "parent": "1"
  }
}

GET join_highlight/_search
{
  "query": {
    "has_child": {
      "type": "answer",
      "query": {
        "match": {
          "text": "answer"
        }
      },
      "inner_hits": {
        "highlight": {
          "fields": {
            "text": {}
          }
        }
      }
    }
  }
}