elasticsearch/docs/reference/query-languages/query-dsl/query-dsl-has-child-query.md

---

navigation_title: "Has child" mapped_pages:

• https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-has-child-query.html ---

Has child query [query-dsl-has-child-query]

Returns parent documents whose joined child documents match a provided query. You can create parent-child relationships between documents in the same index using a join field mapping.

::::{warning} Because it performs a join, the has_child is slow compared to other queries. Its performance degrades as the number of matching child documents pointing to unique parent documents increases. Each has_child query in a search can increase query time significantly.

If you care about query performance, do not use this query. If you need to use the has_child query, use it as rarely as possible.

::::

Example request [has-child-query-ex-request]

Index setup [has-child-index-setup]

To use the has_child query, your index must include a join field mapping. For example:

PUT /my-index-000001
{
  "mappings": {
    "properties": {
      "my-join-field": {
        "type": "join",
        "relations": {
          "parent": "child"
        }
      }
    }
  }
}

Example query [has-child-query-ex-query]

GET /_search
{
  "query": {
    "has_child": {
      "type": "child",
      "query": {
        "match_all": {}
      },
      "max_children": 10,
      "min_children": 2,
      "score_mode": "min"
    }
  }
}

Top-level parameters for has_child [has-child-top-level-params]

type : (Required, string) Name of the child relationship mapped for the join field.

query : (Required, query object) Query you wish to run on child documents of the type field. If a child document matches the search, the query returns the parent document.

ignore_unmapped : (Optional, Boolean) Indicates whether to ignore an unmapped type and not return any documents instead of an error. Defaults to false.

If false, {{es}} returns an error if the type is unmapped.

You can use this parameter to query multiple indices that may not contain the type.

max_children : (Optional, integer) Maximum number of child documents that match the query allowed for a returned parent document. If the parent document exceeds this limit, it is excluded from the search results.

min_children : (Optional, integer) Minimum number of child documents that match the query required to match the query for a returned parent document. If the parent document does not meet this limit, it is excluded from the search results.

score_mode : (Optional, string) Indicates how scores for matching child documents affect the root parent document’s relevance score. Valid values are:

none (Default) : Do not use the relevance scores of matching child documents. The query assigns parent documents a score of 0.

avg : Use the mean relevance score of all matching child documents.

max : Uses the highest relevance score of all matching child documents.

min : Uses the lowest relevance score of all matching child documents.

sum : Add together the relevance scores of all matching child documents.

Notes [has-child-query-notes]

Sorting [has-child-query-performance]

You cannot sort the results of a has_child query using standard sort options.

If you need to sort returned documents by a field in their child documents, use a function_score query and sort by _score. For example, the following query sorts returned documents by the click_count field of their child documents.

GET /_search
{
  "query": {
    "has_child": {
      "type": "child",
      "query": {
        "function_score": {
          "script_score": {
            "script": "_score * doc['click_count'].value"
          }
        }
      },
      "score_mode": "max"
    }
  }
}