Elasticsearch Java API(八)－－搜索有相同父id的子文档

需求：

搜索具有相同父id的所有子文档.

数据：

   mapping：

 {
      "mappings": {
        "branch": {},
        "employee": {
          "_parent": {
            "type": "branch"
          }
        }
      }
   }

父文档：

{ "index": { "_id": "london" }}
{ "name": "London Westminster", "city": "London", "country": "UK" }
{ "index": { "_id": "liverpool" }}
{ "name": "Liverpool Central", "city": "Liverpool", "country": "UK" }
{ "index": { "_id": "paris" }}
{ "name": "Champs Élysées", "city": "Paris", "country": "France" }

子文档：

{ "index": { "_id": 1, "parent": "london" }}
{ "name": "Alice Smith", "dob": "1970-10-24", "hobby": "hiking" }

{ "index": { "_id": 2, "parent": "london" }}
{ "name": "Mark Thomas", "dob": "1982-05-16", "hobby": "diving" }

{ "index": { "_id": 3, "parent": "liverpool" }}
{ "name": "Barry Smith", "dob": "1979-04-01", "hobby": "hiking" }

{ "index": { "_id": 4, "parent": "paris" }}
{ "name": "Adrien Grand", "dob": "1987-05-11", "hobby": "horses" }

搜索父id为london的employee：

curl GET company/employee/_search

    "query":{
       "has_parent":{
         "type":"branch",
         "query":{
           "term":{
               "_parent":"london"
           }
         }
       }
     }

}

这样搜没有搜到任何结果.各种尝试都没有成功，后来到stackoverflow上提问得到了答案，正确的搜索：

curl GET company/employee/_search

{
  "query": {
    "has_parent": {
      "type": "branch",
      "query": {
        "ids": {
             "values" : ["london"]
        }
      }
    }
  }

对应的java api：

HasParentQueryBuilder hpqb=QueryBuilders.hasParentQuery("branch",QueryBuilders.idsQuery().ids("london"));

我在stackoverflow上的提问链接：how to search child documents with the same parent
id in Elasticsearch?