ElasticSearch的概述与聚合查询

Elasticsearch是⾯向⽂档(document oriented)的，这意味着它可以存储整个对象或⽂档(document)。然
⽽它不仅仅是存储，还会索引(index)每个⽂档的内容使之可以被搜索。在Elasticsearch中，你可以对⽂
档（⽽⾮成⾏成列的数据）进⾏索引、搜索、排序、过滤。

IK分词器下载地址https://github.com/medcl/elasticsearch-analysis-ik/releases
必须安装和elasticsearch版本一样的ik分词器,否侧会报错,容器闪退

需要聚合查询的字段要添加fielddata = true
复杂查询都使用NativeSearchQueryBuilder

实例代码

实体类
@document(indexName = "car_index", type = "car")
public class Car {
 @Id
 @Field(type = FieldType.Long, store = true)
 private Long id;
 @Field(type = FieldType.Text, store = true, analyzer = "ik_smart")
 private String name;
 @Field(type = FieldType.Text, store = true, analyzer = "ik_smart",
fielddata = true)
 private String color;
 @Field(type = FieldType.Text, store = true, analyzer = "ik_smart",
fielddata = true)
 private String brand;
 @Field(type = FieldType.Double, store = true)
 private Double price;
 。。。
}

dao
public interface CarDao extends ElasticsearchRepository {
}

TEST代码
@Test
public void testQuerySelfAggs(){
 //查询条件的构建器
 NativeSearchQueryBuilder queryBuilder = new
NativeSearchQueryBuilder().withQuery(QueryBuilders.matchAllQuery());
 //排除所有的字段查询，
 queryBuilder.withSourceFilter(new FetchSourceFilter(new String[]
{},null));
 //添加聚合条件
 
queryBuilder.addAggregation(AggregationBuilders.terms("group_by_color").field
("color"));
 //执⾏查询，把查询结果直接转为聚合page
 AggregatedPage aggPage = (AggregatedPage)
carDao.search(queryBuilder.build());
 //从所有的聚合中获取对应名称的聚合
 StringTerms agg = (StringTerms) aggPage.getAggregation("group_by_color");
 //从聚合的结果中获取所有的桶信息
 List buckets = agg.getBuckets();
 for (StringTerms.Bucket bucket : buckets) {
 String brand = bucket.getKeyAsString();
 long docCount = bucket.getDocCount();
 System.out.println("color = " + brand+" 总数："+docCount);
 }
}