ElasticSearch AggregationBuilders java api常用聚会查询 |
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ElasticSearch AggregationBuilders java api常用聚会查询
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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： "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 } } }
索引中的全部数据： 
首先，初始化Builder： SearchRequestBuilder sbuilder = client.prepareSearch("player").setTypes("player");
接下来举例说明各种聚合操作的实现方法，因为在es的api中，多字段上的聚合操作需要用到子聚合(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，最后度了源码才彻底搞清楚T_T），后边会特意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例如要计算每个球队的球员数，如果使用SQL语句，应表达如下： select team, count(*) as player_count from player group by team;ES的java api： TermsBuilder teamAgg= AggregationBuilders.terms("player_count ").field("team"); sbuilder.addAggregation(teamAgg); SearchResponse response = sbuilder.execute().actionGet();
group by多个field 例如要计算每个球队每个位置的球员数，如果使用SQL语句，应表达如下： select team, position, count(*) as pos_count from player group by team, position;ES的java api： 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 例如要计算每个球队年龄最大/最小/总/平均的球员年龄，如果使用SQL语句，应表达如下： select team, max(age) as max_age from player group by team;ES的java api： 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 例如要计算每个球队球员的平均年龄，同时又要计算总年薪，如果使用SQL语句，应表达如下： select team, avg(age)as avg_age, sum(salary) as total_salary from player group by team;ES的java api： 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 例如要计算每个球队总年薪，并按照总年薪倒序排列，如果使用SQL语句，应表达如下： select team, sum(salary) as total_salary from player group by team order by total_salary desc;ES的java api： 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();
需要特别注意的是，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情况下，search执行后，仅返回10条聚合结果，如果想反悔更多的结果，需要在构建TermsBuilder 时指定size： TermsBuilder teamAgg= AggregationBuilders.terms("team").size(15);Aggregation结果的解析/输出 得到response后： Map aggMap = response.getAggregations().asMap(); StringTerms teamAgg= (StringTerms) aggMap.get("keywordAgg"); Iterator 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(); //得到所有子聚合 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，聚合操作主要是调用了SearchRequestBuilder的addAggregation方法，通常是传入一个TermsBuilder，子聚合调用TermsBuilder的subAggregation方法，可以添加的子聚合有TermsBuilder、SumBuilder、AvgBuilder、MaxBuilder、MinBuilder等常见的聚合操作。 从实现上来讲，SearchRequestBuilder在内部保持了一个私有的 SearchSourceBuilder实例， SearchSourceBuilder内部包含一个List，每次调用addAggregation时会调用 SearchSourceBuilder实例，添加一个AggregationBuilder。同样的，TermsBuilder也在内部保持了一个List，调用addAggregation方法（来自父类addAggregation）时会添加一个AggregationBuilder。有兴趣的读者也可以阅读源码的实现。 如果有什么问题，欢迎一起讨论，如果文中有什么错误，欢迎批评指正。 |
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