anchor.diff:          "my_join_field": {
             "type": "join",
             "relations": {
  -            "my_parent": ["my_child", "another_child"]  <1>
  +            "question": ["answer", "comment"]  <1>
             }
           }
         }
  
positive.code: // TEST[continued]
  
  <1> This child document must be on the same shard than its grandparent and parent
  <2> The parent id of this document (must points to an `another_child` document)
  
  
  
negative.code: --------------------------------------------------
  PUT my_index/doc/3?routing=1&refresh <1>
  {
    "text": "This is an answer",
    "my_join_field": {
      "name": "answer", <2>
      "parent": "1" <3>
    }
  }
  
  PUT my_index/doc/4?routing=1&refresh
  {
    "text": "This is another answer",
    "my_join_field": {
      "name": "answer",
      "parent": "1"
    }
  }
  