5.6降級5.5問題

[root@db1 home]# rpm -ivh MySQL-server-5.5.54-1.el6.x86_64.rpm
Preparing...                ########################################### [100%]
Some previous upgrade was not finished:
-rw-r--r-- 1 root root 176 Oct 24 17:20 /var/lib/mysql/RPM_UPGRADE_MARKER
Please check its status, then do
    rm /var/lib/mysql/RPM_UPGRADE_MARKER
before repeating the MySQL upgrade.
error: %pre(MySQL-server-5.5.54-1.el6.x86_64) scriptlet failed, exit status 1
error:   install: %pre scriptlet failed (2), skipping MySQL-server-5.5.54-1.el6

這是說升級文件有以前的任務沒有完成，說明這個版本時以前已經升級了或降級了，現在可以刪除，然後再升級或降級

[root@db1 home]# rm /var/lib/mysql/RPM_UPGRADE_MARKER
rm: remove regular file `/var/lib/mysql/RPM_UPGRADE_MARKER'? yes

1、無法開啓複製

relay-log.info信息與低版本不一致，導致讀取信息錯誤，需要對照低版本vim修改

2、系統表錯誤

171025 13:45:47 [ERROR] /usr/sbin/mysqld: Incorrect information in file: './performance_schema/events_statements_summary_by_digest.frm'
171025 13:45:47 [ERROR] /usr/sbin/mysqld: Incorrect information in file: './performance_schema/host_cache.fr

刪除ib_logfile0,重新啓動，然後運行mysql_upgrade命令修復

如果不能修復，需要導出主庫數據，刪除從庫表，導入進去，

performance_schema，不能導入，mysql庫可以