• 专职DBA-MySQL常用的两种升级方法


    专职DBA-MySQL常用的两种升级方法
    周万春
    
    
    MySQL5.5.54升级到MySQL5.6.35
    
    
    #----------------------------------------------------------------------------------------
    第1种升级方案:in-place原地升级
    1.停止MySQL 5.5.54
    db01 [~] 2020-06-30 23:07:03
    root@pts/0 # mysql -udba -p
    
    mysql> show variables like '%sql_mode%';
    +---------------+-------+
    | Variable_name | Value |
    +---------------+-------+
    | sql_mode      |       |
    +---------------+-------+
    1 row in set (0.00 sec)
    
    mysql> set global innodb_fast_shutdown=0;
    Query OK, 0 rows affected (0.00 sec)
    
    db01 [~] 2020-06-30 23:08:35
    root@pts/2 # /etc/init.d/mysqld stop
    Shutting down MySQL....                                    [  OK  ]
    
    db01 [~] 2020-06-30 23:09:03
    root@pts/2 # ps -ef | grep mysqld | grep -v grep
    
    db01 [~] 2020-06-30 23:09:09
    root@pts/2 # netstat -lnp | grep mysqld
    
    
    2.在my.cnf中添加skip_grant_tables参数
    db01 [~] 2020-06-30 23:09:45
    root@pts/2 # cat /etc/my.cnf 
    [client]
    socket=/home/mysql/data/mysqldata1/sock/mysql.sock # sock文件所在路径
    
    [mysqld]
    user=mysql
    basedir = /usr/local/mysql
    socket=/home/mysql/data/mysqldata1/sock/mysql.sock # sock文件所在路径
    pid-file=/home/mysql/data/mysqldata1/sock/mysql.pid # pid文件所在路径
    datadir=/home/mysql/data/mysqldata1/mydata # 数据文件路径
    tmpdir=/home/mysql/data/mysqldata1/tmpdir # 存放临时文件的路径
    log-error=/home/mysql/data/mysqldata1/log/error.log
    slow_query_log
    slow_query_log_file=/home/mysql/data/mysqldata1/slowlog/slow-query.log
    log-bin=/home/mysql/data/mysqldata1/binlog/mysql-bin
    relay-log=/home/mysql/data/mysqldata1/relaylog/mysql-relay-bin
    innodb_data_home_dir = /home/mysql/data/mysqldata1/innodb_ts
    innodb_log_group_home_dir = /home/mysql/data/mysqldata1/innodb_log
    #innodb_undo_directory = /home/mysql/data/mysqldata1/undo/
    skip_grant_tables
    
    
    3.替换basedir
    db01 [~] 2020-06-30 23:09:49
    root@pts/2 # cd /disk/
    
    db01 [/disk] 2020-06-30 23:11:12
    root@pts/2 # tar -xf mysql-5.6.35-linux-glibc2.5-x86_64.tar.gz -C /home/mysql/program/
    
    db01 [/disk] 2020-06-30 23:11:45
    root@pts/2 # unlink /usr/local/mysql
    
    db01 [/disk] 2020-06-30 23:11:57
    root@pts/2 # ln -s /home/mysql/program/mysql-5.6.35-linux-glibc2.5-x86_64/ /usr/local/mysql
    
    db01 [/disk] 2020-06-30 23:12:11
    root@pts/2 # chown -R mysql:mysql /home/mysql/program/mysql-5.6.35-linux-glibc2.5-x86_64/
    
    
    4.备份数据
    db01 [/disk] 2020-06-30 23:13:12
    root@pts/2 # cd /home/mysql/
    
    db01 [/home/mysql] 2020-06-30 23:14:32
    root@pts/2 # cp -a data data_bak
    
    
    5.启动并升级MySQL
    db01 [~] 2020-06-30 23:16:04
    root@pts/0 # cp -a /usr/local/mysql/support-files/mysql.server /etc/init.d/mysqld
    
    db01 [~] 2020-06-30 23:16:19
    root@pts/0 # chmod +x /etc/init.d/mysqld
    
    db01 [~] 2020-06-30 23:16:29
    root@pts/0 # /etc/init.d/mysqld start
    Starting MySQL..                                           [  OK  ]
    
    db01 [~] 2020-06-30 23:17:22
    root@pts/0 # mysql
    
    mysql> select user(),current_user();
    +--------+----------------+
    | user() | current_user() |
    +--------+----------------+
    | root@  | @              |
    +--------+----------------+
    1 row in set (0.00 sec)
    
    使用mysql_upgrade命令升级数据字典库。注意:使用mysql_upgrade命令时需要用管理员账号,且带上用户名和密码,否则会报出拒绝访问的错误。
    注意:过程中每一步都要输出OK,且最后输出一个总的OK,看到这些OK,就表示所有的数据字典表升级成功了。
    db01 [~] 2020-06-30 23:18:13
    root@pts/0 # mysql_upgrade -uroot -p
    Enter password: 
    Looking for 'mysql' as: mysql
    Looking for 'mysqlcheck' as: mysqlcheck
    Running 'mysqlcheck' with connection arguments: '--socket=/home/mysql/data/mysqldata1/sock/mysql.sock' 
    Warning: Using a password on the command line interface can be insecure.
    Running 'mysqlcheck' with connection arguments: '--socket=/home/mysql/data/mysqldata1/sock/mysql.sock' 
    Warning: Using a password on the command line interface can be insecure.
    mysql.columns_priv                                 OK
    mysql.db                                           OK
    mysql.event                                        OK
    mysql.func                                         OK
    mysql.general_log                                  OK
    mysql.help_category                                OK
    mysql.help_keyword                                 OK
    mysql.help_relation                                OK
    mysql.help_topic                                   OK
    mysql.host                                         OK
    mysql.ndb_binlog_index                             OK
    mysql.plugin                                       OK
    mysql.proc                                         OK
    mysql.procs_priv                                   OK
    mysql.proxies_priv                                 OK
    mysql.servers                                      OK
    mysql.slow_log                                     OK
    mysql.tables_priv                                  OK
    mysql.time_zone                                    OK
    mysql.time_zone_leap_second                        OK
    mysql.time_zone_name                               OK
    mysql.time_zone_transition                         OK
    mysql.time_zone_transition_type                    OK
    mysql.user                                         OK
    Running 'mysql_fix_privilege_tables'...
    Warning: Using a password on the command line interface can be insecure.
    Running 'mysqlcheck' with connection arguments: '--socket=/home/mysql/data/mysqldata1/sock/mysql.sock' 
    Warning: Using a password on the command line interface can be insecure.
    Running 'mysqlcheck' with connection arguments: '--socket=/home/mysql/data/mysqldata1/sock/mysql.sock' 
    Warning: Using a password on the command line interface can be insecure.
    app01.t1                                           OK
    OK
    
    
    6.重启MySQL并访问数据,测试升级之后能否正常访问
    db01 [~] 2020-06-30 23:19:54
    root@pts/0 # cat /etc/my.cnf 
    [client]
    socket=/home/mysql/data/mysqldata1/sock/mysql.sock # sock文件所在路径
    
    [mysqld]
    user=mysql
    basedir = /usr/local/mysql
    socket=/home/mysql/data/mysqldata1/sock/mysql.sock # sock文件所在路径
    pid-file=/home/mysql/data/mysqldata1/sock/mysql.pid # pid文件所在路径
    datadir=/home/mysql/data/mysqldata1/mydata # 数据文件路径
    tmpdir=/home/mysql/data/mysqldata1/tmpdir # 存放临时文件的路径
    log-error=/home/mysql/data/mysqldata1/log/error.log
    slow_query_log
    slow_query_log_file=/home/mysql/data/mysqldata1/slowlog/slow-query.log
    log-bin=/home/mysql/data/mysqldata1/binlog/mysql-bin
    relay-log=/home/mysql/data/mysqldata1/relaylog/mysql-relay-bin
    innodb_data_home_dir = /home/mysql/data/mysqldata1/innodb_ts
    innodb_log_group_home_dir = /home/mysql/data/mysqldata1/innodb_log
    #innodb_undo_directory = /home/mysql/data/mysqldata1/undo/
    #skip_grant_tables
    
    db01 [~] 2020-06-30 23:19:56
    root@pts/0 # /etc/init.d/mysqld restart
    Shutting down MySQL..                                      [  OK  ]
    Starting MySQL.                                            [  OK  ]
    
    db01 [~] 2020-06-30 23:21:19
    root@pts/0 # mysql -udev -p app01
    
    mysql> select user(),current_user();
    +---------------+----------------+
    | user()        | current_user() |
    +---------------+----------------+
    | dev@localhost | dev@%          |
    +---------------+----------------+
    1 row in set (0.00 sec)
    
    mysql> select version();
    +------------+
    | version()  |
    +------------+
    | 5.6.35-log |
    +------------+
    1 row in set (0.00 sec)
    
    mysql> show grants;
    +--------------------------------------------------------------------------------------------------------+
    | Grants for dev@%                                                                                       |
    +--------------------------------------------------------------------------------------------------------+
    | GRANT USAGE ON *.* TO 'dev'@'%' IDENTIFIED BY PASSWORD <secret>                                        |
    | GRANT SELECT, INSERT, UPDATE, DELETE, EXECUTE, CREATE ROUTINE, ALTER ROUTINE ON `app01`.* TO 'dev'@'%' |
    +--------------------------------------------------------------------------------------------------------+
    2 rows in set (0.00 sec)
    
    mysql> select * from t1;
    +----+--------------------------------------+------+------+---------------------+
    | id | c1                                   | c2   | c3   | intime              |
    +----+--------------------------------------+------+------+---------------------+
    |  1 | bf7042b9-bae2-11ea-b650-00163e1693be | db01 | 3306 | 2020-06-30 23:02:42 |
    +----+--------------------------------------+------+------+---------------------+
    1 row in set (0.00 sec)
    
    mysql> insert into t1(c1,c2,c3) values(uuid(),@@hostname,@@port);
    Query OK, 1 row affected, 2 warnings (0.00 sec)
    
    mysql> select * from t1;
    +----+--------------------------------------+------+------+---------------------+
    | id | c1                                   | c2   | c3   | intime              |
    +----+--------------------------------------+------+------+---------------------+
    |  1 | bf7042b9-bae2-11ea-b650-00163e1693be | db01 | 3306 | 2020-06-30 23:02:42 |
    |  2 | 83d8dcbc-bae5-11ea-8ebf-00163e1693be | db01 | 3306 | 2020-06-30 23:22:31 |
    +----+--------------------------------------+------+------+---------------------+
    2 rows in set (0.00 sec)
    
    
    如果需要修改sql_mode值,则修改全局,并把sql_mode加到my.cnf中
    db01 [~] 2020-06-30 23:23:19
    root@pts/0 # mysql -udba -p
    
    mysql> show variables like '%sql_mode%';
    +---------------+------------------------+
    | Variable_name | Value                  |
    +---------------+------------------------+
    | sql_mode      | NO_ENGINE_SUBSTITUTION |
    +---------------+------------------------+
    1 row in set (0.00 sec)
    
    mysql> set global sql_mode='';
    Query OK, 0 rows affected (0.00 sec)
    
    
    #----------------------------------------------------------------------------------------
    第2张升级方案:mysqldump逻辑导出导入升级
    环境准备到MySQL5.5
    db01 [~] 2020-06-30 23:28:22
    root@pts/0 # /etc/init.d/mysqld stop
    Shutting down MySQL..                                      [  OK  ]
    
    db01 [~] 2020-06-30 23:28:34
    root@pts/0 # unlink /usr/local/mysql
    
    db01 [~] 2020-06-30 23:29:10
    root@pts/0 # cd /home/mysql/
    
    db01 [/home/mysql] 2020-06-30 23:29:34
    root@pts/0 # mv data data_5.6
    
    db01 [/home/mysql] 2020-06-30 23:29:51
    root@pts/0 # mv data_bak data
    
    db01 [~] 2020-06-30 23:30:33
    root@pts/0 # ln -s /home/mysql/program/mysql-5.5.54-linux2.6-x86_64/ /usr/local/mysql
    
    db01 [~] 2020-06-30 23:30:46
    root@pts/0 # rm -rf /etc/init.d/mysqld
    
    db01 [~] 2020-06-30 23:30:58
    root@pts/0 # cp -a /usr/local/mysql/support-files/mysql.server /etc/init.d/mysqld
    
    db01 [~] 2020-06-30 23:31:31
    root@pts/0 # /etc/init.d/mysqld start
    Starting MySQL..                                           [  OK  ]
    
    以上MySQL5.5.54数据库环境已经就绪
    
    1.使用mysqldump备份整个实例
    db01 [~] 2020-06-30 23:31:53
    root@pts/0 # mysql -udba -p
    
    mysql> show variables like '%sql_mode%';
    +---------------+-------+
    | Variable_name | Value |
    +---------------+-------+
    | sql_mode      |       |
    +---------------+-------+
    1 row in set (0.00 sec)
    
    mysql> flush table with read lock;
    Query OK, 0 rows affected (0.00 sec)
    
    mysql> set global read_only=ON;
    Query OK, 0 rows affected (0.00 sec)
    
    mysql> q
    Bye
    
    db01 [~] 2020-06-30 23:50:13
    root@pts/4 # mysqldump -udba -p --add-drop-table --routines --events --all-databases --force > /tmp/data-for-upgrade.sql
    Enter password: 
    
    
    2.安装MySQL 5.6.35
    db01 [~] 2020-06-30 23:51:10
    root@pts/4 # /etc/init.d/mysqld stop
    Shutting down MySQL..                                      [  OK  ]
    
    db01 [~] 2020-06-30 23:51:33
    root@pts/4 # ps -ef | grep mysqld | grep -v grep
    
    db01 [~] 2020-06-30 23:51:37
    root@pts/4 # netstat -lnp | grep mysqld
    
    db01 [~] 2020-06-30 23:51:43
    root@pts/4 # unlink /usr/local/mysql
    
    db01 [~] 2020-06-30 23:56:21
    root@pts/0 # ln -s /home/mysql/program/mysql-5.6.35-linux-glibc2.5-x86_64/ /usr/local/mysql
    
    db01 [~] 2020-06-30 23:52:37
    root@pts/4 # cd /home/mysql/
    
    db01 [/home/mysql] 2020-06-30 23:52:54
    root@pts/4 # cp -a data data_bak
    
    db01 [/home/mysql] 2020-06-30 23:53:37
    root@pts/4 # cd data/mysqldata1/
    
    db01 [/home/mysql/data/mysqldata1] 2020-06-30 23:55:03
    root@pts/4 # rm -rf ./{binlog,innodb_log,innodb_ts,log,mydata,slowlog,sock,tmpdir,undo}/*
    
    db01 [/home/mysql/data/mysqldata1] 2020-06-30 23:55:08
    root@pts/4 # tree ./
    ./
    |-- binlog
    |-- innodb_log
    |-- innodb_ts
    |-- log
    |-- mydata
    |-- relaylog
    |-- slowlog
    |-- sock
    |-- tmpdir
    `-- undo
    
    10 directories, 0 files
    
    db01 [/home/mysql/data/mysqldata1] 2020-06-30 23:56:44
    root@pts/0 # cd /usr/local/mysql/
    
    db01 [/usr/local/mysql] 2020-06-30 23:56:47
    root@pts/0 # ./scripts/mysql_install_db --defaults-file=/home/mysql/conf/my.cnf --user=mysql
    
    
    3.导入MySQL 5.5.54的备份数据
    db01 [~] 2020-06-30 23:58:09
    root@pts/0 # rm -rf /etc/init.d/mysqld
    
    db01 [~] 2020-06-30 23:58:14
    root@pts/0 # cp -a /usr/local/mysql/support-files/mysql.server /etc/init.d/mysqld
    
    db01 [~] 2020-06-30 23:58:23
    root@pts/0 # chmod +x /etc/init.d/mysqld
    
    db01 [~] 2020-07-01 00:12:34
    root@pts/0 # cat /etc/my.cnf 
    [client]
    socket=/home/mysql/data/mysqldata1/sock/mysql.sock # sock文件所在路径
    
    [mysqld]
    user=mysql
    basedir = /usr/local/mysql
    socket=/home/mysql/data/mysqldata1/sock/mysql.sock # sock文件所在路径
    pid-file=/home/mysql/data/mysqldata1/sock/mysql.pid # pid文件所在路径
    datadir=/home/mysql/data/mysqldata1/mydata # 数据文件路径
    tmpdir=/home/mysql/data/mysqldata1/tmpdir # 存放临时文件的路径
    log-error=/home/mysql/data/mysqldata1/log/error.log
    slow_query_log
    slow_query_log_file=/home/mysql/data/mysqldata1/slowlog/slow-query.log
    log-bin=/home/mysql/data/mysqldata1/binlog/mysql-bin
    relay-log=/home/mysql/data/mysqldata1/relaylog/mysql-relay-bin
    innodb_data_home_dir = /home/mysql/data/mysqldata1/innodb_ts
    innodb_log_group_home_dir = /home/mysql/data/mysqldata1/innodb_log
    #innodb_undo_directory = /home/mysql/data/mysqldata1/undo/
    skip_grant_tables
    
    db01 [~] 2020-06-30 23:58:33
    root@pts/0 # /etc/init.d/mysqld start
    Starting MySQL.                                            [  OK  ]
    
    db01 [~] 2020-07-01 00:00:24
    root@pts/0 # mysql -f < /tmp/data-for-upgrade.sql
    
    db01 [~] 2020-07-01 00:00:54
    root@pts/0 # echo $?
    0
    
    
    4.执行mysql_upgrade升级数据字典库
    db01 [~] 2020-07-01 00:13:31
    root@pts/0 # mysql_upgrade -uroot -p
    Enter password: 
    Looking for 'mysql' as: mysql
    Looking for 'mysqlcheck' as: mysqlcheck
    Running 'mysqlcheck' with connection arguments: '--socket=/home/mysql/data/mysqldata1/sock/mysql.sock' 
    Warning: Using a password on the command line interface can be insecure.
    Running 'mysqlcheck' with connection arguments: '--socket=/home/mysql/data/mysqldata1/sock/mysql.sock' 
    Warning: Using a password on the command line interface can be insecure.
    mysql.columns_priv                                 OK
    mysql.db                                           OK
    mysql.event                                        OK
    mysql.func                                         OK
    mysql.general_log                                  OK
    mysql.help_category                                OK
    mysql.help_keyword                                 OK
    mysql.help_relation                                OK
    mysql.help_topic                                   OK
    mysql.host                                         OK
    mysql.innodb_index_stats                           OK
    mysql.innodb_table_stats                           OK
    mysql.ndb_binlog_index                             OK
    mysql.plugin                                       OK
    mysql.proc                                         OK
    mysql.procs_priv                                   OK
    mysql.proxies_priv                                 OK
    mysql.servers                                      OK
    mysql.slave_master_info                            OK
    mysql.slave_relay_log_info                         OK
    mysql.slave_worker_info                            OK
    mysql.slow_log                                     OK
    mysql.tables_priv                                  OK
    mysql.time_zone                                    OK
    mysql.time_zone_leap_second                        OK
    mysql.time_zone_name                               OK
    mysql.time_zone_transition                         OK
    mysql.time_zone_transition_type                    OK
    mysql.user                                         OK
    Running 'mysql_fix_privilege_tables'...
    Warning: Using a password on the command line interface can be insecure.
    Running 'mysqlcheck' with connection arguments: '--socket=/home/mysql/data/mysqldata1/sock/mysql.sock' 
    Warning: Using a password on the command line interface can be insecure.
    Running 'mysqlcheck' with connection arguments: '--socket=/home/mysql/data/mysqldata1/sock/mysql.sock' 
    Warning: Using a password on the command line interface can be insecure.
    app01.t1                                           OK
    OK
    
    
    5.重启MySQL并访问数据,测试升级之后能否正常访问
    去掉配置文件中的skip_grant_tables参数并重启MySQL
    db01 [~] 2020-07-01 00:14:29
    root@pts/0 # cat /etc/my.cnf 
    [client]
    socket=/home/mysql/data/mysqldata1/sock/mysql.sock # sock文件所在路径
    
    [mysqld]
    user=mysql
    basedir = /usr/local/mysql
    socket=/home/mysql/data/mysqldata1/sock/mysql.sock # sock文件所在路径
    pid-file=/home/mysql/data/mysqldata1/sock/mysql.pid # pid文件所在路径
    datadir=/home/mysql/data/mysqldata1/mydata # 数据文件路径
    tmpdir=/home/mysql/data/mysqldata1/tmpdir # 存放临时文件的路径
    log-error=/home/mysql/data/mysqldata1/log/error.log
    slow_query_log
    slow_query_log_file=/home/mysql/data/mysqldata1/slowlog/slow-query.log
    log-bin=/home/mysql/data/mysqldata1/binlog/mysql-bin
    relay-log=/home/mysql/data/mysqldata1/relaylog/mysql-relay-bin
    innodb_data_home_dir = /home/mysql/data/mysqldata1/innodb_ts
    innodb_log_group_home_dir = /home/mysql/data/mysqldata1/innodb_log
    #innodb_undo_directory = /home/mysql/data/mysqldata1/undo/
    #skip_grant_tables
    
    db01 [~] 2020-07-01 00:14:32
    root@pts/0 # /etc/init.d/mysqld restart
    Shutting down MySQL..                                      [  OK  ]
    Starting MySQL.                                            [  OK  ]
    
    db01 [~] 2020-07-01 00:15:21
    root@pts/0 # mysql -udev -p app01
    
    mysql> show databases;
    +--------------------+
    | Database           |
    +--------------------+
    | information_schema |
    | app01              |
    +--------------------+
    2 rows in set (0.00 sec)
    
    mysql> select * from t1;
    +----+--------------------------------------+------+------+---------------------+
    | id | c1                                   | c2   | c3   | intime              |
    +----+--------------------------------------+------+------+---------------------+
    |  1 | bf7042b9-bae2-11ea-b650-00163e1693be | db01 | 3306 | 2020-06-30 23:02:42 |
    +----+--------------------------------------+------+------+---------------------+
    1 row in set (0.00 sec)
    
    mysql> insert into t1(c1,c2,c3) values(uuid(),@@hostname,@@port);
    Query OK, 1 row affected, 2 warnings (0.00 sec)
    
    mysql> select * from t1;
    +----+--------------------------------------+------+------+---------------------+
    | id | c1                                   | c2   | c3   | intime              |
    +----+--------------------------------------+------+------+---------------------+
    |  1 | bf7042b9-bae2-11ea-b650-00163e1693be | db01 | 3306 | 2020-06-30 23:02:42 |
    |  2 | 04e0160f-baed-11ea-bff3-00163e1693be | db01 | 3306 | 2020-07-01 00:16:14 |
    +----+--------------------------------------+------+------+---------------------+
    2 rows in set (0.00 sec)
    
    
    db01 [~] 2020-07-01 00:17:03
    root@pts/0 # mysql -udba -p
    
    mysql> show variables like '%sql_mode%';
    +---------------+--------------------------------------------+
    | Variable_name | Value                                      |
    +---------------+--------------------------------------------+
    | sql_mode      | STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION |
    +---------------+--------------------------------------------+
    1 row in set (0.00 sec)
    
    如果需要修改sql_mode值,则修改全局,并把sql_mode加到my.cnf中
    mysql> set global sql_mode='NO_ENGINE_SUBSTITUTION';
    Query OK, 0 rows affected (0.00 sec)
    
    
    
    升级注意事项
    在主库中创建一个带有主键的InnoDB表(低于MySQL 5.7版本的库),针对主键字段设置为null(虽然这个例子不是很恰当,但这里仅限于说明从MySQL 5.6升级到MySQL 5.7需要谨慎,在同一个复制架构中不建议存在多个版本)
    mysql> show create table test;
    ......
    1 row in set (0.00 sec)
    
    mysql> select version();
    ......
    1 row in set (0.00 sec)
    
    mysql> alter table test modify column id int(10) unsigned NULL;
    Query OK, 0 rows affected (0.00 sec)
    Records: 0  Duplicates: 0  Warnings: 0
    
    mysql> show create table test;
    ......
    1 row in set (0.00 sec)
    
    ## 解析binlog查看
    [root@localhost data]# mysqlbinlog -vv mysql-bin.000203
    ......
    
    # 在主库中创建一个带有主键的InnoDB表(高于或等于MySQL 5.7版本的库),针对主键字段设置为null
    mysql> show create table test;
    ......                                                                
    1 row in set (0.00 sec)
    
    mysql> select version();
    ......
    1 row in set (0.00 sec)
    
    mysql> alter table test modify column id int(10) unsigned NULL;
    ERROR 1171 (42000): All parts of a PRIMARY KEY must be NOT NULL; if you need NULL in a key, use UNIQUE instead
    
    MySQL5.7版本不允许对主键设置null属性操作,MySQL5.6版本是允许对主键设置null属性操作的,
    但会在存储引擎内部自动忽略这个动作。
    虽然忽略了这个动作,但是这条语句却执行成功了,已经记录到binlog中。
    如果从库是MySQL5.7,就会在SQL线程重放到这条SQL语句时报错,
    ERROR 1171 (42000): All parts of a PRIMARY KEY must be NOT NULL; if you need NULL in a key, use UNIQUE instead.
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  • 原文地址:https://www.cnblogs.com/zhouwanchun/p/13216967.html
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