Elasticsearch 7.x 去重查詢並返回去重后的總數

mysql去重操作

select distinct age from user;

如果在es中如何去重呢

需要用到Elasticsearch 中的 collapse 可以實現該需求

collapse 官網文檔

java API

SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.collapse(new CollapseBuilder("name.keyword"));

但是有個問題，就是hits的total value不對，對應的還是未去重的數量，其實想要的是去重后的總數

可以借助 Aggregation 中的 cardinality 來實現

java API

SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
AggregationBuilder aggregation = AggregationBuilders.cardinality(DISTINCT_TOTAL_COUNT).field("name.keyword");
searchSourceBuilder.aggregation(aggregation);

獲取去重后的數量

Aggregations aggregations = searchResponse.getAggregations();
Cardinality cardinality = aggregations.get(DISTINCT_TOTAL_COUNT);
System.out.println(cardinality.getValue());

需要注意的是，字段類型得是keyword類型。DISTINCT_TOTAL_COUNT是自定義的屬性

tips: 持續輸出，堅持！