MySQL Binlog Mixed模式記錄成Row格式

背景：

? ? ? 一個簡單的主從結構，主的binlog format是Mixed模式，在執行一條簡單的導入語句時，通過mysqlbinlog導出發現記錄的Binlog全部變成了Row的格式（明明設置的是Mixed），現在就說說在什么情況下Binlog的Mixed模式會轉變記錄成Row格式。

概念：

? ? ? binlog format有三種形式：Statement、Mixed、Row，具體的信息可以自行到網上搜查。

分析（本文碰到的案例）：

查看MySQL binlog format

dba@192.168.111.4 : dba_test 02:33:39>show variables like 'binlog_format%';                                                                                                   +---------------+-------+
| Variable_name | Value |
+---------------+-------+
| binlog_format | MIXED |
+---------------+-------+

測試語句：

dba@192.168.111.4 : dba_test 02:24:14>create table tmp_test(id int,name varchar(64),age int,primary key(id)) engine = innodb;
Query OK, 0 rows affected (0.05 sec)dba@192.168.111.4 : dba_test 02:24:23>insert into tmp_test values(1,'aaa',11);
Query OK, 1 row affected (0.02 sec)dba@192.168.111.4 : dba_test 02:25:17>insert into tmp_test values(2,'bbb',22);
Query OK, 1 row affected (0.02 sec)dba@192.168.111.4 : dba_test 02:25:23>insert into tmp_test values(3,'ccc',33);
Query OK, 1 row affected (0.01 sec)dba@192.168.111.4 : dba_test 02:25:28>insert into tmp_test values(4,'ddd',44);
Query OK, 1 row affected (0.01 sec)dba@192.168.111.4 : dba_test 02:25:34>insert into tmp_test values(5,'eee',55);
Query OK, 1 row affected (0.01 sec)dba@192.168.111.4 : dba_test 02:25:42>select * from tmp_test;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | aaa  |   11 |
|  2 | bbb  |   22 |
|  3 | ccc  |   33 |
|  4 | ddd  |   44 |
|  5 | eee  |   55 |
+----+------+------+
5 rows in set (0.01 sec)dba@192.168.111.4 : dba_test 02:25:50>create table tmp_test_bak(id int,name varchar(64),age int,primary key(id)) engine = innodb;
Query OK, 0 rows affected (0.03 sec)dba@192.168.111.4 : dba_test 02:26:31>insert into tmp_test_bak select * from tmp_test;   ###記錄成了Row模式
Query OK, 5 rows affected (0.03 sec)
Records: 5  Duplicates: 0  Warnings: 0

Binlog 記錄圖：

問題來了，我想要出來的binlog format是Statement，而不是Row。而一條insert into tb select * from ta的簡單語句在Mixed模式下記錄了Row模式的binlog。原因是什么？

首先確實在一些特定的情況下，Mixed會被轉換成Row模式：

. 當 DML 語句更新一個 NDB 表時；
. 當函數中包含 UUID() 時；
. 2 個及以上包含 AUTO_INCREMENT 字段的表被更新時；
. 執行 INSERT DELAYED 語句時；
. 用 UDF 時；
. 視圖中必須要求運用 row 時，例如建立視圖時使用了 UUID() 函數；

上面來自網絡，有興趣的可以自己測試測試。而對于本文中的sql，符合不了上面的條件，但binlog也記錄成了Row格式。所以還是很奇怪為什么binlog格式被轉換了，日常工作的時候有遇到過執行一條sql，會報一個warning：

Warning: Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT

難道因為這個導致轉換的？因為上面的SQL可以重現，沒有報warning，所以這個情況排除。根據經驗想到了一個參數：innodb_locks_unsafe_for_binlog，看到里面講到事務隔離級別，那就看看隔離級別的情況：

dba@192.168.111.4 : dba_test 05:46:56>select @@global.tx_isolation;
+-----------------------+
| @@global.tx_isolation |
+-----------------------+
| READ-COMMITTED        |
+-----------------------+
1 row in set (0.01 sec)dba@192.168.111.4 : dba_test 06:36:45>select @@session.tx_isolation;
+------------------------+
| @@session.tx_isolation |
+------------------------+
| READ-COMMITTED         |
+------------------------+
1 row in set (0.01 sec)

看到隔離級別是提交讀，即不可重復讀。把事務隔離級別設置成默認的?REPEATABLE READ：

dba@192.168.111.4 : dba_test 06:41:02>set session transaction isolation level REPEATABLE READ;                                                                              
Query OK, 0 rows affected (0.14 sec)dba@192.168.111.4 : dba_test 06:41:42>select @@session.tx_isolation;
+------------------------+
| @@session.tx_isolation |
+------------------------+
| REPEATABLE-READ        |
+------------------------+
1 row in set (0.00 sec)

再執行測試里的SQL，發現這時候Mixed的binlog記錄了Statement格式，正常了，符合預期了。難道就是這個事務隔離級別的問題引起的？在手冊里發現了這句：

Note
In MySQL 5.7, when READ COMMITTED isolation level is used, or the deprecated innodb_locks_unsafe_for_binlog system variable is enabled,

there is no InnoDB gap locking except for foreign-key constraint checking and duplicate-key checking. Also, record locks for nonmatching

rows are released after MySQL has evaluated the WHERE condition.If you use READ COMMITTED or enable innodb_locks_unsafe_for_binlog, you must use row-based binary logging.

展開可以看例子：

dba@192.168.111.4 : dba_test 06:49:27>select @@session.tx_isolation;
+------------------------+
| @@session.tx_isolation |
+------------------------+
| REPEATABLE-READ        |
+------------------------+
1 row in set (0.01 sec)dba@192.168.111.4 : dba_test 06:49:29>create table tmp_test_bak(id int,name varchar(64),age int,primary key(id)) engine = innodb;                                                
Query OK, 0 rows affected (0.14 sec)dba@192.168.111.4 : dba_test 06:49:34>insert into tmp_test_bak values(1,'aaa',11);
Query OK, 1 row affected (0.13 sec)dba@192.168.111.4 : dba_test 06:49:41>insert into tmp_test_bak values(2,'bbb',22);
Query OK, 1 row affected (0.11 sec)dba@192.168.111.4 : dba_test 06:49:41>insert into tmp_test_bak values(3,'ccc',33);
Query OK, 1 row affected (0.11 sec)dba@192.168.111.4 : dba_test 06:49:42>insert into tmp_test_bak values(4,'ddd',44);
Query OK, 1 row affected (0.11 sec)dba@192.168.111.4 : dba_test 06:49:42>insert into tmp_test_bak values(5,'eee',55);
Query OK, 1 row affected (0.13 sec)BINLOG:
root@dba:/var/log/mysql# mysqlbinlog mysql-bin.000007 |grep "tmp_test_bak"
create table tmp_test_bak(id int,name varchar(64),age int,primary key(id)) engine = innodb
insert into tmp_test_bak values(1,'aaa',11)
insert into tmp_test_bak values(2,'bbb',22)
insert into tmp_test_bak values(3,'ccc',33)
insert into tmp_test_bak values(4,'ddd',44)
insert into tmp_test_bak values(5,'eee',55)#############################
#############################dba@192.168.111.4 : dba_test 06:49:43>set session transaction isolation level READ COMMITTED;
Query OK, 0 rows affected (0.01 sec)dba@192.168.111.4 : dba_test 06:50:21>flush logs;                                                                                                                                Query OK, 0 rows affected (0.21 sec)dba@192.168.111.4 : dba_test 06:50:23>create table tmp_test(id int,name varchar(64),age int,primary key(id)) engine = innodb;
Query OK, 0 rows affected (0.14 sec)dba@192.168.111.4 : dba_test 06:50:49>insert into tmp_test values(1,'aaa',11);
Query OK, 1 row affected (0.13 sec)dba@192.168.111.4 : dba_test 06:50:54>insert into tmp_test values(2,'bbb',22);
Query OK, 1 row affected (0.11 sec)dba@192.168.111.4 : dba_test 06:50:54>insert into tmp_test values(3,'ccc',33);
Query OK, 1 row affected (0.11 sec)dba@192.168.111.4 : dba_test 06:50:54>insert into tmp_test values(4,'ddd',44);
Query OK, 1 row affected (0.11 sec)dba@192.168.111.4 : dba_test 06:50:54>insert into tmp_test values(5,'eee',55);
Query OK, 1 row affected (0.12 sec)BINLOG:
root@pubmed2:/var/log/mysql# mysqlbinlog -vv mysql-bin.000008 |grep "tmp_test"
create table tmp_test(id int,name varchar(64),age int,primary key(id)) engine = innodb
#160426 18:50:54 server id 1  end_log_pos 395     Table_map: `pubmed_data`.`tmp_test` mapped to number 44
### INSERT INTO `pubmed_data`.`tmp_test`
#160426 18:50:54 server id 1  end_log_pos 597     Table_map: `pubmed_data`.`tmp_test` mapped to number 44
### INSERT INTO `pubmed_data`.`tmp_test`
#160426 18:50:54 server id 1  end_log_pos 799     Table_map: `pubmed_data`.`tmp_test` mapped to number 44
### INSERT INTO `pubmed_data`.`tmp_test`
#160426 18:50:54 server id 1  end_log_pos 1001     Table_map: `pubmed_data`.`tmp_test` mapped to number 44
### INSERT INTO `pubmed_data`.`tmp_test`
#160426 18:50:55 server id 1  end_log_pos 1203     Table_map: `pubmed_data`.`tmp_test` mapped to number 44
### INSERT INTO `pubmed_data`.`tmp_test`