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.

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"
        }
      }
    }
  }
}

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

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, Elasticsearch 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.

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"
    }
  }
}