OpenSearch/docs/java-api/aggregations/metrics/tophits-aggregation.asciidoc

[[java-aggs-metrics-tophits]]
==== Top Hits Aggregation

Here is how you can use
{ref}/search-aggregations-metrics-top-hits-aggregation.html[Top Hits Aggregation]
with Java API.


===== Prepare aggregation request

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

[source,java]
--------------------------------------------------
AggregationBuilder aggregation =
    AggregationBuilders
        .terms("agg").field("gender")
        .subAggregation(
            AggregationBuilders.topHits("top")
        );
--------------------------------------------------

You can use most of the options available for standard search such as `from`, `size`, `sort`, `highlight`, `explain`...

[source,java]
--------------------------------------------------
AggregationBuilder aggregation =
    AggregationBuilders
        .terms("agg").field("gender")
        .subAggregation(
            AggregationBuilders.topHits("top")
                .setExplain(true)
                .setSize(1)
                .setFrom(10)
        );
--------------------------------------------------

===== Use aggregation response

Import Aggregation definition classes:

[source,java]
--------------------------------------------------
import org.elasticsearch.search.aggregations.bucket.terms.Terms;
import org.elasticsearch.search.aggregations.metrics.tophits.TopHits;
--------------------------------------------------

[source,java]
--------------------------------------------------
// sr is here your SearchResponse object
Terms agg = sr.getAggregations().get("agg");

// For each entry
for (Terms.Bucket entry : agg.getBuckets()) {
    String key = entry.getKey();                    // bucket key
    long docCount = entry.getDocCount();            // Doc count
    logger.info("key [{}], doc_count [{}]", key, docCount);

    // We ask for top_hits for each bucket
    TopHits topHits = entry.getAggregations().get("top");
    for (SearchHit hit : topHits.getHits().getHits()) {
        logger.info(" -> id [{}], _source [{}]", hit.getId(), hit.getSourceAsString());
    }
}
--------------------------------------------------

This will basically produce for the first example:

[source,text]
--------------------------------------------------
key [male], doc_count [5107]
 -> id [AUnzSZze9k7PKXtq04x2], _source [{"gender":"male",...}]
 -> id [AUnzSZzj9k7PKXtq04x4], _source [{"gender":"male",...}]
 -> id [AUnzSZzl9k7PKXtq04x5], _source [{"gender":"male",...}]
key [female], doc_count [4893]
 -> id [AUnzSZzM9k7PKXtq04xy], _source [{"gender":"female",...}]
 -> id [AUnzSZzp9k7PKXtq04x8], _source [{"gender":"female",...}]
 -> id [AUnzSZ0W9k7PKXtq04yS], _source [{"gender":"female",...}]
--------------------------------------------------