问题描述：
在实际项目中，查询Top10数据的场景非常常见，比如查询票房前十的电影，销售榜前十的商品等。
那么在ES中如何查询Top10的数据呢？
问题分析：
一般Top10问题，都可以转化成先排序再取排行前10的问题，那么实现就简单了。
数据准备
创建索引book，获取价格最贵的3本书的信息。
PUT book { "mappings": { "properties": { "name": { "type": "text", "analyzer": "ik_smart" }, "price": { "type": "double" } } } }
PUT /book/_bulk { "create": { } } {"name": "java编程思想","price": 100} { "create": { } } {"name": "ES实战","price": 120} { "create": { } } {"name": "ES从入门到精通","price": 60} { "create": { } } {"name": "微服务架构 设计模式","price": 160} { "create": { } } {"name": "架构真经","price": 90} { "create": { } } {"name": "spring boot实战","price": 50} { "create": { } } {"name": "高性能mysql","price": 80}
实现方案：
1、SQL查询
POST /_sql?format=txt { "query": "SELECT * FROM book ORDER BY price DESC", "fetch_size": 3 } POST /_sql?format=txt { "query": "SELECT * FROM (SELECT * FROM book ORDER BY price DESC ) limit 3" }
查询结果：
2、DSL查询
POST /_sql/translate { "query": "SELECT * FROM book ORDER BY price DESC", "fetch_size": 3 }
转化结果：
{ "size" : 3, "_source" : { "includes" : [ "name", "price" ], "excludes" : [ ] }, "sort" : [ { "price" : { "order" : "desc", "missing" : "_first", "unmapped_type" : "double" } } ] }
完整DSL语句：
POST /book/_search { "size" : 3, "_source" : { "includes" : [ "name", "price" ], "excludes" : [ ] }, "sort" : [ { "price" : { "order" : "desc", "missing" : "_first", "unmapped_type" : "double" } } ] }
