共计 6466 个字符，预计需要花费 17 分钟才能阅读完成。
起源：https://developer.aliyun.com/…
背景
本文次要测试 MySQL 执行 update 语句时，针对与原数据（即未修改）雷同的 update 语句会在 MySQL 外部从新执行吗？
测试环境
- MySQL5.7.25
- Centos 7.4
binlog_format 为 ROW
参数
root@localhost : (none) 04:53:15> show variables like 'binlog_row_image';
+------------------+-------+
| Variable_name | Value |
+------------------+-------+
| binlog_row_image | FULL |
+------------------+-------+
1 row in set (0.00 sec)
root@localhost : (none) 04:53:49> show variables like 'binlog_format';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| binlog_format | ROW |
+---------------+-------+
1 row in set (0.00 sec)
root@localhost : test 05:15:14> show variables like 'transaction_isolation';
+-----------------------+-----------------+
| Variable_name | Value |
+-----------------------+-----------------+
| transaction_isolation | REPEATABLE-READ |
+-----------------------+-----------------+
1 row in set (0.00 sec)测试步骤
session1
root@localhost : test 04:49:48> begin;
Query OK, 0 rows affected (0.00 sec)
root@localhost : test 04:49:52> select * from test where id =1;
+----+------+------+------+
| id | sid | mid | name |
+----+------+------+------+
| 1 | 999 | 871 | NW |
+----+------+------+------+
1 row in set (0.00 sec)
root@localhost : (none) 04:54:03> show engine innodb status\Gshow master status\G
...
---
LOG
---
Log sequence number 12090390
Log flushed up to 12090390
Pages flushed up to 12090390
Last checkpoint at 12090381
0 pending log flushes, 0 pending chkp writes
33 log i/o's done, 0.00 log i/o's/second
*************************** 1. row ***************************
File: mysql-bin.000001
Position: 154
Binlog_Do_DB:
Binlog_Ignore_DB:
Executed_Gtid_Set:
1 row in set (0.00 sec)session2
root@localhost : test 04:47:45> update test set sid=55 where id =1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
root@localhost : (none) 04:54:03> show engine innodb status\Gshow master status\G
...
---
LOG
---
Log sequence number 12091486
Log flushed up to 12091486
Pages flushed up to 12091486
Last checkpoint at 12091477
0 pending log flushes, 0 pending chkp writes
39 log i/o's done, 0.00 log i/o's/second
*************************** 1. row ***************************
File: mysql-bin.000001
Position: 500
Binlog_Do_DB:
Binlog_Ignore_DB:
Executed_Gtid_Set: 8392d215-4928-11e9-a751-0242ac110002:1
1 row in set (0.00 sec)session1
root@localhost : test 04:49:57> update test set sid=55 where id =1;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
root@localhost : (none) 04:54:03> show engine innodb status\Gshow master status\G
...
---
LOG
---
Log sequence number 12091486
Log flushed up to 12091486
Pages flushed up to 12091486
Last checkpoint at 12091477
0 pending log flushes, 0 pending chkp writes
39 log i/o's done, 0.00 log i/o's/second
*************************** 1. row ***************************
File: mysql-bin.000001
Position: 500
Binlog_Do_DB:
Binlog_Ignore_DB:
Executed_Gtid_Set: 8392d215-4928-11e9-a751-0242ac110002:1
1 row in set (0.00 sec)
root@localhost : test 04:52:05> select * from test where id =1;
+----+------+------+------+
| id | sid | mid | name |
+----+------+------+------+
| 1 | 999 | 871 | NW |
+----+------+------+------+
1 row in set (0.00 sec)
root@localhost : test 04:52:42> commit;
Query OK, 0 rows affected (0.00 sec)
root@localhost : test 04:52:52> select * from test where id =1;
+----+------+------+------+
| id | sid | mid | name |
+----+------+------+------+
| 1 | 55 | 871 | NW |
+----+------+------+------+
1 row in set (0.00 sec)总结
- 在 binlog_format=row 和 binlog_row_image=FULL 时，因为 MySQL 须要在 binlog 外面记录所有的字段，所以在读数据的时候就会把所有数据都读出来，那么反复数据的 update 不会执行。即 MySQL 调用了 InnoDB 引擎提供的“批改为 (1,55)”这个接口，然而引擎发现值与原来雷同，不更新，间接返回
binlog_format 为 STATEMENT
参数
root@localhost : (none) 04:53:15> show variables like 'binlog_row_image';
+------------------+-------+
| Variable_name | Value |
+------------------+-------+
| binlog_row_image | FULL |
+------------------+-------+
1 row in set (0.00 sec)
root@localhost : (none) 05:16:08> show variables like 'binlog_format';
+---------------+-----------+
| Variable_name | Value |
+---------------+-----------+
| binlog_format | STATEMENT |
+---------------+-----------+
1 row in set (0.00 sec)
root@localhost : test 05:15:14> show variables like 'transaction_isolation';
+-----------------------+-----------------+
| Variable_name | Value |
+-----------------------+-----------------+
| transaction_isolation | REPEATABLE-READ |
+-----------------------+-----------------+
1 row in set (0.00 sec)测试步骤
session1
root@localhost : test 05:16:42> begin;
Query OK, 0 rows affected (0.00 sec)
root@localhost : test 05:16:44> select * from test where id =1;
+----+------+------+------+
| id | sid | mid | name |
+----+------+------+------+
| 1 | 111 | 871 | NW |
+----+------+------+------+
1 row in set (0.00 sec)
root@localhost : (none) 05:16:51> show engine innodb status\Gshow master status\G
...
---
LOG
---
Log sequence number 12092582
Log flushed up to 12092582
Pages flushed up to 12092582
Last checkpoint at 12092573
0 pending log flushes, 0 pending chkp writes
45 log i/o's done, 0.00 log i/o's/second
*************************** 1. row ***************************
File: mysql-bin.000001
Position: 154
Binlog_Do_DB:
Binlog_Ignore_DB:
Executed_Gtid_Set:
1 row in set (0.00 sec)session2
root@localhost : test 05:18:30> update test set sid=999 where id =1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
root@localhost : (none) 05:18:47> show engine innodb status\Gshow master status\G
...
---
LOG
---
Log sequence number 12093678
Log flushed up to 12093678
Pages flushed up to 12093678
Last checkpoint at 12093669
0 pending log flushes, 0 pending chkp writes
51 log i/o's done, 0.14 log i/o's/second
*************************** 1. row ***************************
File: mysql-bin.000001
Position: 438
Binlog_Do_DB:
Binlog_Ignore_DB:
Executed_Gtid_Set: 8392d215-4928-11e9-a751-0242ac110002:1
1 row in set (0.00 sec)session1
root@localhost : test 05:16:47> update test set sid=999 where id =1;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
root@localhost : (none) 05:20:03> show engine innodb status\Gshow master status\G
...
---
LOG
---
Log sequence number 12094504
Log flushed up to 12094504
Pages flushed up to 12094504
Last checkpoint at 12094495
0 pending log flushes, 0 pending chkp writes
56 log i/o's done, 0.00 log i/o's/second
*************************** 1. row ***************************
File: mysql-bin.000001
Position: 438
Binlog_Do_DB:
Binlog_Ignore_DB:
Executed_Gtid_Set: 8392d215-4928-11e9-a751-0242ac110002:1
1 row in set (0.00 sec)
root@localhost : test 05:19:33> select * from test where id =1;
+----+------+------+------+
| id | sid | mid | name |
+----+------+------+------+
| 1 | 999 | 871 | NW |
+----+------+------+------+
1 row in set (0.00 sec)
root@localhost : test 05:20:44> commit;
Query OK, 0 rows affected (0.01 sec)
root@localhost : test 05:20:57> select * from test where id =1;
+----+------+------+------+
| id | sid | mid | name |
+----+------+------+------+
| 1 | 999 | 871 | NW |
+----+------+------+------+
1 row in set (0.00 sec)总结
- 在 binlog_format=statement 和 binlog_row_image=FULL 时，InnoDB 外部认真执行了 update 语句，即“把这个值批改成 (1,999)“这个操作，该加锁的加锁，该更新的更新。
近期热文举荐：
1.1,000+ 道 Java 面试题及答案整顿 (2022 最新版)
2. 劲爆！Java 协程要来了。。。
3.Spring Boot 2.x 教程，太全了！
4. 别再写满屏的爆爆爆炸类了，试试装璜器模式，这才是优雅的形式！！
5.《Java 开发手册（嵩山版）》最新公布，速速下载！
感觉不错，别忘了顺手点赞 + 转发哦！
正文完
