MySQL mysqlbinlog解析出的SQL语句被注释是怎么回事

一网友反馈使用mysqlbinlog解析出的二进制日志中的内容中，有些SQL语句有#注释的情况，这个是怎么回事呢？我们通过实验来了解一下具体细节情况，如下所示，实验环境为5.6.20-enterprise-commercial-advanced-log

# whereis mysqlbinlog

mysqlbinlog: /usr/bin/mysqlbinlog /usr/share/man/man1/mysqlbinlog.1.gz

我们先在参数文件my.cnf里面设置binlog_format=ROW ，然后重启一下MySQL服务

mysql> show variables like 'binlog_format';+---------------+-------+| Variable_name | Value |+---------------+-------+| binlog_format | ROW   |+---------------+-------+1 row in set (0.00 sec)mysql> show master status;+----------------------+----------+--------------+------------------+-------------------+| File                 | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |+----------------------+----------+--------------+------------------+-------------------+| DB-Server-bin.000005 |      512 |              |                  |                   |+----------------------+----------+--------------+------------------+-------------------+1 row in set (0.00 sec)mysql>mysql> drop table kkk;Query OK, 0 rows affected (0.01 sec)mysql> create table kkk (id int ,name varchar(32));Query OK, 0 rows affected (0.02 sec)mysql> insert into kkk-> select 100, 'name' union all-> select 200, 'kerry' union all-> select 300, 'k3';Query OK, 3 rows affected (0.02 sec)Records: 3  Duplicates: 0  Warnings: 0mysql>

默认情况下只能看到一些经过base-64编码的信息，如下所示：

[root@DB-Server ~]# /usr/bin/mysqlbinlog/data/mysql/DB-Server-bin.000005

use `MyDB`/*!*/;SET TIMESTAMP=1530288296/*!*/;DROP TABLE `kkk` /* generated by server *//*!*/;# at 628#180629 12:05:14 server id 1  end_log_pos 745 CRC32 0xc6037a3f  Query   thread_id=3     exec_time=0     error_code=0SET TIMESTAMP=1530288314/*!*/;create table kkk (id int ,name varchar(32))/*!*/;# at 745#180629 12:06:07 server id 1  end_log_pos 817 CRC32 0x74fd4efb  Query   thread_id=3     exec_time=0     error_code=0SET TIMESTAMP=1530288367/*!*/;BEGIN/*!*/;# at 817#180629 12:06:07 server id 1  end_log_pos 866 CRC32 0xfb1391dd  Table_map: `MyDB`.`kkk` mapped to number 73# at 866#180629 12:06:07 server id 1  end_log_pos 930 CRC32 0xecb4e812  Write_rows: table id 73 flags: STMT_END_FBINLOG '71g2WxMBAAAAMQAAAGIDAAAAAEkAAAAAAAEABE15REIAA2trawACAw8CYAAD3ZET+w==71g2Wx4BAAAAQAAAAKIDAAAAAEkAAAAAAAEAAgAC//xkAAAABG5hbWX8yAAAAAVrZXJyefwsAQAAAmszEui07A=='/*!*/;# at 930#180629 12:06:07 server id 1  end_log_pos 961 CRC32 0x7ca988e3  Xid = 37COMMIT/*!*/;DELIMITER ;# End of log fileROLLBACK /* added by mysqlbinlog */;/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;

mysqlbinlog有一个参数--verbose(或-v)，将自动生成带注释的SQL语句(在行事件中重构伪SQL语句)，其实这个并非原始SQL语句，而是伪SQL，如果使用这个参数两次(如-v -v)，则输出列的描述信息，会生成字段的类型、长度、是否为null等属性信息：

-v, --verboseReconstruct pseudo-SQL statements out of row events. -v-v adds comments on column data types.

[root@DB-Server ~]# /usr/bin/mysqlbinlog -v /data/mysql/DB-Server-bin.000005

如上所示，其实这里的SQL语句不是原始SQL语句，那么能否看到原始SQL语句呢？答案是可以，但是必须设置系统变量binlog_rows_query_log_events

mysql> show variables like 'binlog_rows_query_log_events';+------------------------------+-------+| Variable_name                | Value |+------------------------------+-------+| binlog_rows_query_log_events | OFF   |+------------------------------+-------+1 row in set (0.00 sec)mysql> set binlog_rows_query_log_events=1;Query OK, 0 rows affected (0.00 sec)mysql> flush logs;Query OK, 0 rows affected (0.01 sec)mysql>  show master status;+----------------------+----------+--------------+------------------+-------------------+| File                 | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |+----------------------+----------+--------------+------------------+-------------------+| DB-Server-bin.000026 |      120 |              |                  |                   |+----------------------+----------+--------------+------------------+-------------------+1 row in set (0.00 sec)mysql>mysql> insert into kkk select 600, 'k600';Query OK, 1 row affected (0.00 sec)Records: 1  Duplicates: 0  Warnings: 0

[root@DB-Server ~]# /usr/bin/mysqlbinlog--base64-output=DECODE-ROWS-v -v /data/mysql/DB-Server-bin.000026

在二进制日志格式为MIXED模式下，简单测试没有发现SQL被注释的情况，记录的都是原始的SQL语句。不清楚是否存在某些特殊情况也会出现这种情况。网友反馈腾讯云的MySQL在MIXED模式下，也会出现这种情况，不过没有使用过腾讯的MySQL，手头也没有测试环境，只能作罢！