PageHelper：百万级数据查询优化

方案一：不需要总页数时去掉count

PageHelper.startPage(1, 10);
// 去掉count
PageHelper.getLocalPage().setCount(false);
List<String> userList = userDAO.listUser();
PageInfo pageInfo = new PageInfo(baseParamDOList);

PageInfo结果示例：

{"total": -1,"list": [],"pageNum": 1,"pageSize": 15,"size": 15,"startRow": 1,"endRow": 15,"pages": 1,"prePage": 0,"nextPage": 0,"isFirstPage": true,"isLastPage": true,"hasPreviousPage": false,"hasNextPage": false,"navigatePages": 8,"navigatepageNums": [1],"navigateFirstPage": 1,"navigateLastPage": 1
}

方案二：使用Oracle9iDialect

PageHelper5.2.0提供了2个Dialect，分别是oracle、oracle9i：

-- OracleDialect 外层控制范围
WHERE ROW_ID <= ? AND ROW_ID > ?-- Oracle9iDialect 内外分别控制范围
TMP_PAGE WHERE ROWNUM <= ? ) WHERE ROW_ID > ?

配置文件：

<property name="helperDialect" value="oracle"/>
<!-- 或 -->
<property name="helperDialect" value="oracle9i"/>

参考：
pagehelper之百万级数据查询优化

PageHelper5在Oracle查询变慢的问题解决

Mybatis 5.2.0