現有索引資料：

index:school

type:student

---------------------------------------------------

{"grade":"1", "class":"1", "name":"xiao 1"}

{"grade":"1", "class":"1", "name":"xiao 2"}

{"grade":"1", "class":"2", "name":"xiao 3"}

{"grade":"1", "class":"2", "name":"xiao 4"}

{"grade":"1", "class":"2", "name":"xiao 5"}

Java分組統計年級和班級學生個數，如SQL: SELECT grade,class,count(1) FROM student GROUP BY grade,class;

package test;

import java.util.Iterator;

import java.util.Map;

import org.elasticsearch.action.search.SearchRequestBuilder;

import org.elasticsearch.action.search.SearchResponse;

import org.elasticsearch.action.search.SearchType;

import org.elasticsearch.search.aggregations.Aggregation;

import org.elasticsearch.search.aggregations.AggregationBuilders;

import org.elasticsearch.search.aggregations.bucket.terms.StringTerms;

import org.elasticsearch.search.aggregations.bucket.terms.Terms.Bucket;

import org.elasticsearch.search.aggregations.bucket.terms.TermsBuilder;

import org.junit.Test;

import utils.NesUtils;

public class TestAggregation

{

@Test

public void testAggregation()

{

SearchRequestBuilder srb = NesUtils.getSearcher("school");

srb.setTypes("student");

srb.setSearchType(SearchType.COUNT);

TermsBuilder gradeTermsBuilder = AggregationBuilders.terms("gradeAgg").field("grade");

TermsBuilder classTermsBuilder = AggregationBuilders.terms("classAgg").field("class");

gradeTermsBuilder.subAggregation(classTermsBuilder);

srb.addAggregation(gradeTermsBuilder);

SearchResponse sr = srb.execute().actionGet();

Map<String, Aggregation> aggMap = sr.getAggregations().asMap();

StringTerms gradeTerms = (StringTerms) aggMap.get("gradeAgg");

Iterator<Bucket> gradeBucketIt = gradeTerms.getBuckets().iterator();

while(gradeBucketIt.hasNext())

{

Bucket gradeBucket = gradeBucketIt.next();

System.out.println(gradeBucket.getKey() + "年級有" + gradeBucket.getDocCount() +"個學生。");

StringTerms classTerms = (StringTerms) gradeBucket.getAggregations().asMap().get("classAgg");

Iterator<Bucket> classBucketIt = classTerms.getBuckets().iterator();

while(classBucketIt.hasNext())

{

Bucket classBucket = classBucketIt.next();

System.out.println(gradeBucket.getKey() + "年級" +classBucket.getKey() + "班有" + classBucket.getDocCount() +"個學生。");

}

System.out.println();

}

}

}

執行完成輸出結果

---------------------------------------------------

1年級有5個學生。

1年級2班有3個學生。

1年級1班有2個學生。