背景

本文主要測(cè)試MySQL執(zhí)行update語(yǔ)句時(shí)，針對(duì)與原數(shù)據(jù)（即未修改）相同的update語(yǔ)句會(huì)在MySQL內(nèi)部重新執(zhí)行嗎？

測(cè)試環(huán)境

• MySQL5.7.25
• Centos 7.4

binlog_format為ROW

參數(shù)

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)

測(cè)試步驟

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.000001Position: 154Binlog_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: 0root@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.000001Position: 500Binlog_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: 0root@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.000001Position: 500Binlog_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)

總結(jié)

• 在binlog_format=row和binlog_row_image=FULL時(shí)，由于MySQL 需要在 binlog 里面記錄所有的字段，所以在讀數(shù)據(jù)的時(shí)候就會(huì)把所有數(shù)據(jù)都讀出來(lái)，那么重復(fù)數(shù)據(jù)的update不會(huì)執(zhí)行。即MySQL 調(diào)用了 InnoDB 引擎提供的“修改為 (1,55)”這個(gè)接口，但是引擎發(fā)現(xiàn)值與原來(lái)相同，不更新，直接返回

binlog_format為STATEMENT

參數(shù)

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)

測(cè)試步驟

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.000001Position: 154Binlog_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: 0root@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.000001Position: 438Binlog_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: 0root@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.000001Position: 438Binlog_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)

總結(jié)

• 在binlog_format=statement和binlog_row_image=FULL時(shí)，InnoDB內(nèi)部認(rèn)真執(zhí)行了update語(yǔ)句，即“把這個(gè)值修改成 (1,999)“這個(gè)操作，該加鎖的加鎖，該更新的更新。

?

一站式開(kāi)發(fā)者服務(wù)，海量學(xué)習(xí)資源0元起！
阿里熱門(mén)開(kāi)源項(xiàng)目、機(jī)器學(xué)習(xí)干貨、開(kāi)發(fā)者課程/工具、小微項(xiàng)目、移動(dòng)研發(fā)等海量資源；更有開(kāi)發(fā)者福利Kindle、技術(shù)圖書(shū)幸運(yùn)抽獎(jiǎng)，100%中--》https://www.aliyun.com/acts/product-section-2019/developer?utm_content=g_1000047140

原文鏈接
本文為云棲社區(qū)原創(chuàng)內(nèi)容，未經(jīng)允許不得轉(zhuǎn)載。

總結(jié)

以上是生活随笔為你收集整理的MySQL中update修改数据与原数据相同会再次执行吗的全部?jī)?nèi)容，希望文章能夠幫你解決所遇到的問(wèn)題。

如果覺(jué)得生活随笔網(wǎng)站內(nèi)容還不錯(cuò)，歡迎將生活随笔推薦給好友。