MySQL mysqlbinlog解析出的SQL語句被注釋是怎么回事
一網友反饋使用mysqlbinlog解析出的二進制日志中的內容中，有些SQL語句有#注釋的情況，這個是怎么回事呢？我們通過實驗來了解一下具體細節情況，如下所示，實驗環境為5.6.20-enterprise-commercial-advanced-log
# whereis mysqlbinlog
mysqlbinlog: /usr/bin/mysqlbinlog /usr/share/man/man1/mysqlbinlog.1.gz
我們先在參數文件my.cnf里面設置binlog_format=ROW ，然后重啟一下MySQL服務
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>
默認情況下只能看到一些經過base-64編碼的信息，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有一個參數--verbose(或-v)，將自動生成帶注釋的SQL語句（在行事件中重構偽SQL語句），其實這個並非原始SQL語句，而是偽SQL，如果使用這個參數兩次(如-v -v)，則輸出列的描述信息，會生成字段的類型、長度、是否為null等屬性信息：
-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，其實這里的SQL語句不是原始SQL語句，那么能否看到原始SQL語句呢？答案是可以，但是必須設置系統變量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
在二進制日志格式為MIXED模式下，簡單測試沒有發現SQL被注釋的情況，記錄的都是原始的SQL語句。不清楚是否存在某些特殊情況也會出現這種情況。網友反饋騰訊雲的MySQL在MIXED模式下，也會出現這種情況，不過沒有使用過騰訊的MySQL，手頭也沒有測試環境，只能作罷！