前几天帮同事解决一个案例，在主从复制环境下，从库上的MySQL版本号是5.5.5，遇到下面的错误：
~~~
#其他非相关信息我都隐藏掉了
[([email protected])]> show slave status \G;
Slave_IO_Running: Yes
Slave_SQL_Running: No
Last_Errno: 1064
Last_Error: Error 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '6e86db84_14847168f19__8000' at line 1' on query. Default database: 'act'. Query: 'SAVEPOINT 6e86db84_14847168f19__8000'
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 1064
Last_SQL_Error: Error 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '6e86db84_14847168f19__8000' at line 1' on query. Default database: 'act_log'. Query: 'SAVEPOINT 6e86db84_14847168f19__8000'
~~~
第一感觉是遇到保留关键字了，不过看到这么长的字符串，不应该是保留关键字才对。
经过尝试，最后发现是字符串中的 “e” 这个字符如果存在就可能会报错，看起来应该是bug才对了。
在MySQL的bug系统里确实找到了这个bug，不过看bug描述，在5.5版本中应该是已经修复了才对，看来太不靠谱了呀~~
关于这个bug：[Savepoint identifier is occasionally considered as floating point numbers](http://bugs.mysql.com/bug.php?id=55962 "Savepoint identifier is occasionally considered as floating point numbers")
其实除了升级版本外，解决方法也很简单，把savepoint后面的 identifier 字符串用反引号(波浪号的下档键，英文叫做 backticks 键)引用起来就行。
例如：
~~~
savepoint `6e86db84_14847168f19__8000`;
~~~
这样就可以了。
这个案例也提示我们，在写SQL时，涉及到数据库、表、字段、identifier 等名称时，最好是都能用反引号引用，确保可用。
曾经看到线上数据表有个字段名是 check ，这个名字在MySQL里很早就已经是保留关键字，幸好开发同学比较靠谱，都加上了反引号。
关于savepoint的2个bug：
[Savepoint Identifier should be enclosed with backticks](http://bugs.mysql.com/bug.php?id=55961 "Savepoint Identifier should be enclosed with backticks")
[Savepoint identifier is occasionally considered as floating point numbers](http://bugs.mysql.com/bug.php?id=55962 "Savepoint identifier is occasionally considered as floating point numbers")