55_Has_parent.asciidoc

Finding children by their parents

While a nested query can only ever return 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:

GET /company/employee/_search
{
  "query": {
    "has_parent": {
      "type": "branch", (1)
      "query": {
        "match": {
          "country": "UK"
        }
      }
    }
  }
}

1. Returns children who have parents of type branch.

The has_parent query also supports the score_mode, but it only accepts two settings: none (the default) and score. Each child can only have 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).

has_parent filter

The has_parent filter works in the same way as the has_parent query, except that it doesn’t support the score_mode parameter. It can only be used in `filter context'' — such as inside a `filtered query —  and it behaves like any other filter: it includes or excludes, but doesn’t score.

While the results of a has_parent filter are not cached, the usual caching rules apply to the filter inside the has_parent filter.