The query can‘t be routed to all backend servers because it includes SELECT and SQL variable modific

Posted 2021-08-11 雅冰石

一 问题描述

同事反馈，通过maxscale执行sql的时候，报错。

sql内容：

SELECT 
  *,
  @rownum := @rownum + 1 AS r 
FROM
  (SELECT 
    '0dca79c35b' AS id 
  FROM
    DUAL) T

报错：

SQL Error (1064): Routing query to backend failed. See the error log for further detail

maxscale日志报错：

2021-07-12 15:39:05   warning: (244392) The query can't be routed to all backend servers because it includes SELECT and SQL variable modifications which is not supported. Set use_sql_variables_in=master or split the query to two, where SQL variable modifications are done in the first and the SELECT in the second one.

二 解决办法

修改maxscale配置文件，在读写分离服务配置下面，添加一行配置：

use_sql_variables_in=master

示例：

 #重启maxscale

systemctl restart maxscale