elastic java api 聚合_ElasticSearch java API - 聚合查询

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:"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:

elastic java api 聚合_ElasticSearch java API - 聚合查询_第1张图片

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。

注:文中使用的Elastic Search API版本为2.3.2

你可能感兴趣的:(elastic,java,api,聚合)