[[children-agg]] === Children Aggregation

Parent-child supports a http://bit.ly/1xtpjaz[`children` aggregation] as ((("aggregations", "children aggregation")))((("children aggregation")))((("parent-child relationship", "children aggregation")))a direct analog to the nested aggregation discussed in <>. A parent aggregation (the equivalent of reverse_nested) is not supported.

This example demonstrates how we could determine the favorite hobbies of our employees by country:

[source,json]

GET /company/branch/_search?search_type=count { "aggs": { "country": { "terms": { <1> "field": "country" }, "aggs": { "employees": { "children": { <2> "type": "employee" }, "aggs": { "hobby": { "terms": { <3> "field": "employee.hobby" } } } } } } }

}

<1> The country field in the branch documents.

<2> The children aggregation joins the parent documents with their associated children of type employee.

<3> The hobby field from the employee child documents.