java elasticsearch聚合查詢實例

現有索引數據：

index:school
type:student
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{"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();
        }

    }
}

運行完成輸出結果

---------------------------------------------------
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。