The parent_id query can be used to find child documents which belong to a particular parent.
Given the following mapping definition:
PUT my_index
{
  "mappings": {
    "properties": {
      "my_join_field": {
        "type": "join",
        "relations": {
          "my_parent": "my_child"
        }
      }
    }
  }
}
PUT my_index/_doc/1?refresh
{
  "text": "This is a parent document",
  "my_join_field": "my_parent"
}
PUT my_index/_doc/2?routing=1&refresh
{
  "text": "This is a child document",
  "my_join_field": {
    "name": "my_child",
    "parent": "1"
  }
}GET /my_index/_search
{
  "query": {
    "parent_id": {
      "type": "my_child",
      "id": "1"
    }
  }
}This query has two required parameters:
| 
 | 
The child type name, as specified in the  | 
| 
 | The ID of the parent document. | 
| 
 | 
When set to  |