GET /company/employee/_search
{
  "query": {
    "has_parent": {
      "type": "branch", (1)
      "query": {
        "match": {
          "country": "UK"
        }
      }
    }
  }
}Finding Children by Their Parents
While a nested query can always return only the root document as a result,
parent and child documents are independent and each can be queried
independently.  The has_child query allows us to return parents based on
data in their children, and the has_parent query returns children based on
data in their parents.
It looks very similar to the has_child query.  This example returns
employees who work in the UK:
- 
Returns children who have parents of type branch
The has_parent query also supports the score_mode, but it accepts only two
settings: none (the default) and score.  Each child can have only one
parent, so there is no need to reduce multiple scores into a single score for
the child.  The choice is simply between using the score (score) or not
(none).