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Elastic Docs ›Elasticsearch Guide [7.2] ›Query DSL ›Joining queries

Has parent query

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Has parent query

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

Because it performs a join, the has_parent query is slow compared to other queries. Its performance degrades as the number of matching parent documents increases. Each has_parent query in a search can increase query time significantly.

Example request

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Index setup

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

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

Example query

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GET /my-index/_search
{
    "query": {
        "has_parent" : {
            "parent_type" : "parent",
            "query" : {
                "term" : {
                    "tag" : {
                        "value" : "Elasticsearch"
                    }
                }
            }
        }
    }
}

Top-level parameters for has_parent

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parent_type
(Required, string) Name of the parent relationship mapped for the join field.
query
(Required, query object) Query you wish to run on parent documents of the parent_type field. If a parent document matches the search, the query returns its child documents.
score

(Optional, boolean) Indicates whether the relevance score of a matching parent document is aggregated into its child documents. Defaults to false.

If false, Elasticsearch ignores the relevance score of the parent document. Elasticsearch also assigns each child document a relevance score equal to the query's boost, which defaults to 1.

If true, the relevance score of the matching parent document is aggregated into its child documents' relevance scores.

ignore_unmapped

(Optional, boolean) Indicates whether to ignore an unmapped parent_type and not return any documents instead of an error. Defaults to false.

If false, Elasticsearch returns an error if the parent_type is unmapped.

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

Notes

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Sorting

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

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

GET /_search
{
    "query": {
        "has_parent" : {
            "parent_type" : "parent",
            "score" : true,
            "query" : {
                "function_score" : {
                    "script_score": {
                        "script": "_score * doc['view_count'].value"
                    }
                }
            }
        }
    }
}
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