[[java-aggs]]
== Aggregations

Elasticsearch provides a full Java API to play with aggregations. See the
{ref}/search-aggregations.html[Aggregations guide].

Use the factory for aggregation builders (`AggregationBuilders`) and add each aggregation
you want to compute when querying and add it to your search request:

[source,java]
--------------------------------------------------
SearchResponse sr = node.client().prepareSearch()
        .setQuery( /* your query */ )
        .addAggregation( /* add an aggregation */ )
        .execute().actionGet();
--------------------------------------------------

Note that you can add more than one aggregation. See
{ref}/search-search.html[Search Java API] for details.

To build aggregation requests, use `AggregationBuilders` helpers. Just import them
in your class:

[source,java]
--------------------------------------------------
import org.elasticsearch.search.aggregations.AggregationBuilders;
--------------------------------------------------

=== Structuring aggregations

As explained in the
{ref}/search-aggregations.html[Aggregations guide], you can define
sub aggregations inside an aggregation.

An aggregation could be a metrics aggregation or a bucket aggregation.

For example, here is a 3 levels aggregation composed of:

* Terms aggregation (bucket)
* Date Histogram aggregation (bucket)
* Average aggregation (metric)

[source,java]
--------------------------------------------------
SearchResponse sr = node.client().prepareSearch()
    .addAggregation(
        AggregationBuilders.terms("by_country").field("country")
        .subAggregation(AggregationBuilders.dateHistogram("by_year")
            .field("dateOfBirth")
            .dateHistogramInterval(DateHistogramInterval.YEAR)
            .subAggregation(AggregationBuilders.avg("avg_children").field("children"))
        )
    )
    .execute().actionGet();
--------------------------------------------------

=== Metrics aggregations

include::aggregations/metrics.asciidoc[]

=== Bucket aggregations

include::aggregations/bucket.asciidoc[]
