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: 0
mysql>
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=0
SET 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=0
SET 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_F
BINLOG '
71g2WxMBAAAAMQAAAGIDAAAAAEkAAAAAAAEABE15REIAA2trawACAw8CYAAD3ZET+w==
71g2Wx4BAAAAQAAAAKIDAAAAAEkAAAAAAAEAAgAC//xkAAAABG5hbWX8yAAAAAVrZXJyefwsAQAA
AmszEui07A==
'/*!*/;
# at 930
#180629 12:06:07 server id 1 end_log_pos 961 CRC32 0x7ca988e3 Xid = 37
COMMIT/*!*/;
DELIMITER ;
# End of log file
ROLLBACK /* 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, --verbose Reconstruct 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！