OpenSearch/docs/java-api/aggregations/bucket/reverse-nested-aggregation.asciidoc

[[java-aggs-bucket-reverse-nested]]
==== Reverse Nested Aggregation

Here is how you can use
{ref}/search-aggregations-bucket-reverse-nested-aggregation.html[Reverse Nested Aggregation]
with Java API.


===== Prepare aggregation request

Here is an example on how to create the aggregation request:

[source,java]
--------------------------------------------------
AggregationBuilder aggregation =
    AggregationBuilders
        .nested("agg", "resellers")
        .subAggregation(
                AggregationBuilders
                        .terms("name").field("resellers.name")
                        .subAggregation(
                                AggregationBuilders
                                        .reverseNested("reseller_to_product")
                        )
        );
--------------------------------------------------


===== Use aggregation response

Import Aggregation definition classes:

[source,java]
--------------------------------------------------
import org.elasticsearch.search.aggregations.bucket.nested.Nested;
import org.elasticsearch.search.aggregations.bucket.nested.ReverseNested;
import org.elasticsearch.search.aggregations.bucket.terms.Terms;
--------------------------------------------------

[source,java]
--------------------------------------------------
// sr is here your SearchResponse object
Nested agg = sr.getAggregations().get("agg");
Terms name = agg.getAggregations().get("name");
for (Terms.Bucket bucket : name.getBuckets()) {
    ReverseNested resellerToProduct = bucket.getAggregations().get("reseller_to_product");
    resellerToProduct.getDocCount(); // Doc count
}
--------------------------------------------------