ElasticSearch AggregationBuilders java api经常使用聚会查询

以球员信息为例，player索引的player type包含5个字段，姓名，年龄，薪水，球队，场上位置。
index的mapping为：

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"mappings" : {      "player" : {          "properties" : {              "name" : {                  "index" :  "not_analyzed" ,                  "type" :  "string"              },              "age" : {                  "type" :  "integer"              },              "salary" : {                  "type" :  "integer"              },              "team" : {                  "index" :  "not_analyzed" ,                  "type" :  "string"              },              "position" : {                  "index" :  "not_analyzed" ,                  "type" :  "string"              }          },          "_all" : {              "enabled" :  false          }      } }

　　

索引中的所有数据：

 
首先，初始化Builder：

1	SearchRequestBuilder sbuilder = client.prepareSearch( "player" ).setTypes( "player" );

　　

接下来举例说明各类聚合操做的实现方法，由于在es的api中，多字段上的聚合操做须要用到子聚合(subAggregation)，初学者可能找不到方法（网上资料比较少，笔者在这个问题上折腾了两天，最后度了源码才完全搞清楚T_T），后边会特地说明多字段聚合的实现方法。另外，聚合后的排序也会单独说明。

• group by/count

例如要计算每一个球队的球员数，若是使用SQL语句，应表达以下：

select team, count(*) as player_count from player group by team;

ES的java api：

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TermsBuilder teamAgg= AggregationBuilders.terms( "player_count " ).field( "team" ); sbuilder.addAggregation(teamAgg); SearchResponse response = sbuilder.execute().actionGet();

　　

 

• group by多个field

例如要计算每一个球队每一个位置的球员数，若是使用SQL语句，应表达以下：

select team, position, count(*) as pos_count from player group by team, position;

ES的java api：

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TermsBuilder teamAgg= AggregationBuilders.terms( "player_count " ).field( "team" ); TermsBuilder posAgg= AggregationBuilders.terms( "pos_count" ).field( "position" ); sbuilder.addAggregation(teamAgg.subAggregation(posAgg)); SearchResponse response = sbuilder.execute().actionGet();

　　

 

• max/min/sum/avg

例如要计算每一个球队年龄最大/最小/总/平均的球员年龄，若是使用SQL语句，应表达以下：

select team, max(age) as max_age from player group by team;

ES的java api：

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TermsBuilder teamAgg= AggregationBuilders.terms( "player_count " ).field( "team" ); MaxBuilder ageAgg= AggregationBuilders.max( "max_age" ).field( "age" ); sbuilder.addAggregation(teamAgg.subAggregation(ageAgg)); SearchResponse response = sbuilder.execute().actionGet();

　　

 

• 对多个field求max/min/sum/avg

例如要计算每一个球队球员的平均年龄，同时又要计算总年薪，若是使用SQL语句，应表达以下：

select team, avg(age)as avg_age, sum(salary) as total_salary from player group by team;

ES的java api：

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TermsBuilder teamAgg= AggregationBuilders.terms( "team" ); AvgBuilder ageAgg= AggregationBuilders.avg( "avg_age" ).field( "age" ); SumBuilder salaryAgg= AggregationBuilders.avg( "total_salary " ).field( "salary" ); sbuilder.addAggregation(teamAgg.subAggregation(ageAgg).subAggregation(salaryAgg)); SearchResponse response = sbuilder.execute().actionGet();

　　

• 聚合后对Aggregation结果排序

例如要计算每一个球队总年薪，并按照总年薪倒序排列，若是使用SQL语句，应表达以下：

select team, sum(salary) as total_salary from player group by team order by total_salary desc;

ES的java api：

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TermsBuilder teamAgg= AggregationBuilders.terms( "team" ).order(Order.aggregation( "total_salary " ,  false ); SumBuilder salaryAgg= AggregationBuilders.avg( "total_salary " ).field( "salary" ); sbuilder.addAggregation(teamAgg.subAggregation(salaryAgg)); SearchResponse response = sbuilder.execute().actionGet();

　　

须要特别注意的是，排序是在TermAggregation处执行的，Order.aggregation函数的第一个参数是aggregation的名字，第二个参数是boolean型，true表示正序，false表示倒序。 

• Aggregation结果条数的问题

默认状况下，search执行后，仅返回10条聚合结果，若是想反悔更多的结果，须要在构建TermsBuilder 时指定size：

TermsBuilder teamAgg= AggregationBuilders.terms("team").size(15);

 

• Aggregation结果的解析/输出

获得response后：

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Map<String, Aggregation> aggMap = response.getAggregations().asMap(); StringTerms teamAgg= (StringTerms) aggMap.get( "keywordAgg" ); Iterator<Bucket> teamBucketIt = teamAgg.getBuckets().iterator(); while  (teamBucketIt .hasNext()) { Bucket buck = teamBucketIt .next(); //球队名 String team = buck.getKey(); //记录数 long  count = buck.getDocCount(); //获得全部子聚合 Map subaggmap = buck.getAggregations().asMap(); //avg值获取方法 double  avg_age= ((InternalAvg) subaggmap.get( "avg_age" )).getValue(); //sum值获取方法 double  total_salary = ((InternalSum) subaggmap.get( "total_salary" )).getValue(); //... //max/min以此类推 }

　　

 

• 总结

综上，聚合操做主要是调用了SearchRequestBuilder的addAggregation方法，一般是传入一个TermsBuilder，子聚合调用TermsBuilder的subAggregation方法，能够添加的子聚合有TermsBuilder、SumBuilder、AvgBuilder、MaxBuilder、MinBuilder等常见的聚合操做。 从实现上来说，SearchRequestBuilder在内部保持了一个私有的 SearchSourceBuilder实例， SearchSourceBuilder内部包含一个List<AbstractAggregationBuilder>，每次调用addAggregation时会调用 SearchSourceBuilder实例，添加一个AggregationBuilder。一样的，TermsBuilder也在内部保持了一个List<AbstractAggregationBuilder>，调用addAggregation方法（来自父类addAggregation）时会添加一个AggregationBuilder。有兴趣的读者也能够阅读源码的实现。