具體升級過程
下面以Linux系統為例，展示下具體升級過程。我的系統是CentOS7.7，原版本是MySQL5.7.23，以In-Place方式直接升級到MySQL8.0.19。
下載解壓安裝包
官網下載對應版本的tar包，可通過wget下載或者本地下載后上傳。
下載地址：
https://downloads.mysql.com/archives/community/
選擇mysql-8.0.19-linux-glibc2.12-x86_64.tar.xz
執行以下步驟解壓tar包：
# 安裝包上傳至原安裝包目錄下 我的是/usr/local/ cd /usr/local/ # 解壓安裝包 xz -d mysql-8.0.19-linux-glibc2.12-x86_64.tar.xz tar -xvf mysql-8.0.19-linux-glibc2.12-x86_64.tar # 文件夾重命名為mysql8 mv mysql-8.0.19-linux-glibc2.12-x86_64 mysql8 # 更改文件夾所屬 chown -R mysql.mysql /usr/local/mysql8/
更改配置文件my.cnf
因5.7版本與8.0版本參數有所不同，為了能順利升級，我們需要更改部分配置參數。主要注意sql_mode、basedir、密碼認證插件及字符集設置，其他參數最好還是按照原5.7的來，不需要做調整。下面展示下更改后的配置文件：
注意：如果my.cnf 中配置了query_cache_size需要將其注銷
# 最后幾個for8.0的參數要格外注意 [mysqld] user = mysql datadir = /data/mysql/data port = 3306 socket = /data/mysql/tmp/mysql.sock pid-file = /data/mysql/tmp/mysqld.pid tmpdir = /data/mysql/tmp skip_name_resolve = 1 max_connections = 2000 group_concat_max_len = 1024000 lower_case_table_names = 1 log_timestamps=SYSTEM max_allowed_packet = 32M binlog_cache_size = 4M sort_buffer_size = 2M read_buffer_size = 4M join_buffer_size = 4M tmp_table_size = 96M max_heap_table_size = 96M max_length_for_sort_data = 8096 default_time_zone = '+8:00' #logs server-id = 1003306 log-error = /data/mysql/logs/error.log slow_query_log = 1 slow_query_log_file = /data/mysql/logs/slow.log long_query_time = 3 log-bin = /data/mysql/logs/binlog binlog_format = row log_bin_trust_function_creators = 1 gtid_mode = ON enforce_gtid_consistency = ON #for8.0 sql_mode = STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION character-set-server = utf8 collation_server = utf8_general_ci basedir = /usr/local/mysql8 skip_ssl default_authentication_plugin=mysql_native_password
執行升級程序
所有前置工作准備好后就可以開始正式升級了，不過升級前還是建議先全庫備份下。萬事俱備后，按照如下指示進行正式升級。
# 進入原5.7 mysql命令行 正確關閉數據庫 mysql> select version(); +------------+ | version() | +------------+ | 5.7.23-log | +------------+ 1 row in set (0.00 sec) mysql> show variables like 'innodb_fast_shutdown'; +----------------------+-------+ | Variable_name | Value | +----------------------+-------+ | innodb_fast_shutdown | 1 | +----------------------+-------+ 1 row in set (0.00 sec) # 確保數據都刷到硬盤上，更改成0 mysql> set global innodb_fast_shutdown=0; Query OK, 0 rows affected (0.00 sec) mysql> shutdown; Query OK, 0 rows affected (0.00 sec) mysql> exit Bye # 退出至終端 用mysql8.0.19客戶端直接啟動 [root@centos ~]# /usr/local/mysql8/bin/mysqld_safe --defaults-file=/etc/my.cnf --user=mysql & [1] 23333 [root@centos ~]# 2020-05-20T07:07:02.337626Z mysqld_safe Logging to '/data/mysql/logs/error.log'. 2020-05-20T07:07:02.366244Z mysqld_safe Starting mysqld daemon with databases from /data/mysql/data # 可觀察下錯誤日志看是否報錯 然后重新登錄測試 [root@centos ~]# mysql -uroot -p123456 mysql: [Warning] Using a password on the command line interface can be insecure. Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 17 Server version: 8.0.19 MySQL Community Server - GPL Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> select version(); +-----------+ | version() | +-----------+ | 8.0.19 | +-----------+ 1 row in set (0.00 sec)
環境變量修改
因basedir由/usr/local/mysql變成了/usr/local/mysql8，故相關環境變量推薦修改下。可按照以下步驟來操作驗證：
# 修改mysql服務啟動項配置 vi /etc/init.d/mysql # 修改basedir目錄 basedir=/usr/local/mysql8 # 修改PATH變量 vi /etc/profile # 將PATH中的/usr/local/mysql/bin改為/usr/local/mysql8/bin # 生效驗證 [root@centos ~]# source /etc/profile [root@centos ~]# which mysql /usr/local/mysql8/bin/mysql [root@centos ~]# mysql -V mysql Ver 8.0.19 for linux-glibc2.12 on x86_64 (MySQL Community Server - GPL)
總結：
至此，我們的數據庫由5.7成功升級至8.0！對比MySQL安裝過程及升級過程，發現二者很相似，其實升級過程並不復雜，復雜的是升級后的驗證及兼容測試，特別是對於復雜的業務庫，MySQL版本升級還是要小心的。真實環境建議先升級從庫，驗證無誤后再逐步對主庫進行升級。
參考鏈接：http://blog.itpub.net/31401187/viewspace-2693699/