searchAfter深度分页

es一次只能查1万条数据，如果超过1万，会报错如下：

        "reason": {
          "type": "query_phase_execution_exception",
          "reason": "Result window is too large, from + size must be less than or equal to: [10000] but was [10001]. See the scroll api for a more efficient way to request large data sets. This limit can be set by changing the [index.max_result_window] index level setting."
        }

可以调整es配置的index.max_result_window这个参数，来查询更多的数据，但这并不是很好的办法，最好使用 searchAfter.

searchAfter作用类似于以下sql语句：

-- 查询第10001--10005条数据
SELECT * FROM  t_user  order by name,birthDay  LIMIT 10000,5;

dsl

• 第一次查询，查询1--10000条数据，找出第10000条数据的排序字段结果

GET /user_info/_search
{
	"size": 10000,
	"sort": [{
		"name": {
			"order": "asc"
		}
	 },
	 {
		"birthDay": {
			"order": "desc"
		}
	}]
}

• 第二次查询，根据上面最后一条数据的排序字段，查询出第 10001--20000条数据;
  多了一个search_after的查询条件，对应的排序字段为第一步查出来的最后一条数据(也就是第10000条数据)的排序字段

GET /user_info/_search
{
	"size": 10000,
	"sort": [{
		"name": {
			"order": "asc"
		}
	 },
	 {
		"birthDay": {
			"order": "desc"
		}
	}],
	"search_after": ["wang", "1993-12-01"]
}

java代码

    public SearchSourceBuilder searchAfterTest() {
        SearchSourceBuilder searc = new SearchSourceBuilder().size(10000);

        BoolQueryBuilder boolQuery = QueryBuilders.boolQuery();
//        boolQuery.filter(QueryBuilders.termQuery("province", "深圳市"));

        searc.sort("name", SortOrder.ASC).sort("birthDay", SortOrder.DESC);

        String[] searchAfter = new String[]{"wang", "1993-12-01"};
        searc.searchAfter(searchAfter);

        return searc.query(boolQuery);
    }