背景：

? ? ? 一個簡單的主從結(jié)構(gòu)，主的binlog format是Mixed模式，在執(zhí)行一條簡單的導(dǎo)入語句時，通過mysqlbinlog導(dǎo)出發(fā)現(xiàn)記錄的Binlog全部變成了Row的格式（明明設(shè)置的是Mixed），現(xiàn)在就說說在什么情況下Binlog的Mixed模式會轉(zhuǎn)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(wǎng)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(zhuǎn)換成Row模式：

. 當 DML 語句更新一個 NDB 表時； . 當函數(shù)中包含 UUID() 時； . 2 個及以上包含 AUTO_INCREMENT 字段的表被更新時； . 執(zhí)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(shù)；

上面來自網(wǎng)絡(luò)，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(zhuǎn)換了，日常工作的時候有遇到過執(zhí)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(dǎo)致轉(zhuǎn)換的？因為上面的SQL可以重現(xiàn)，沒有報warning，所以這個情況排除。根據(jù)經(jīng)驗想到了一個參數(shù)：innodb_locks_unsafe_for_binlog，看到里面講到事務(wù)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(fù)讀。把事務(wù)隔離級別設(shè)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(zhí)行測試里的SQL，發(fā)現(xiàn)這時候Mixed的binlog記錄了Statement格式，正常了，符合預(yù)期了。難道就是這個事務(wù)隔離級別的問題引起的？在手冊里發(fā)現(xiàn)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` View Code

經(jīng)過測試，在5.1、5.5、5.6都有這個情況，可能這個本身就不是問題。:)

總結(jié)：

? ? ? 除了上面說的一些條件影響binlog的記錄格式外（Statement 到 Row），事務(wù)隔離也影響這binlog的記錄格式行為。

轉(zhuǎn)載于:https://www.cnblogs.com/zhoujinyi/p/5436250.html

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