MySQL表rename导致的外键问题

Posted 2021-02-11

背景：
由于zabbix监控的问题图形展示很慢，对zabbix 库的events表进行了清理，清理过程采用了原表rename成bak表，重建events表后，将备份表部分数据导入到新表中。

后发现zabbix平台无法报警，无法恢复报警，日志类似报错：
 2315:20190301:104933.609 [Z3005] query failed: [1452] Cannot add or update a child row: a foreign key constraint fails (`zabbix`.`event_recovery`, CONSTRAINT `c_event_recovery_1` FOREIGN KEY (`eventid`) REFERENCES `events_bak20190225` (`eventid`) ON DELETE CASCADE) [insert into event_recovery (eventid,r_eventid,correlationid,c_eventid,userid) values (4242559,4242581,null,null,null),(4242561,4242580,null,null,null),(4242447,4242580,null,null,null);

原来rename后，关联的外键表的约束竟然一并修改成了归档表的关联。
处理方法如下：
查看哪些表建立外键时关联了归档表

select  distinct TABLE_NAME,CONSTRAINT_NAME,REFERENCED_TABLE_NAME from INFORMATION_SCHEMA.KEY_COLUMN_USAGE where TABLE_SCHEMA  =‘zabbix‘ and CONSTRAINT_name != ‘PRIMARY‘ and REFERENCED_TABLE_NAME like ‘event%‘;
+----------------+--------------------+-----------------------+
| TABLE_NAME     | CONSTRAINT_NAME    | REFERENCED_TABLE_NAME |
+----------------+--------------------+-----------------------+
| acknowledges   | c_acknowledges_2   | events                |
| alerts         | c_alerts_2         | events                |
| alerts         | c_alerts_5         | events                |
| event_recovery | c_event_recovery_1 | events                |
| event_recovery | c_event_recovery_2 | events                |
| event_recovery | c_event_recovery_3 | events                |
| event_tag      | c_event_tag_1      | events_bak20190225    |
| problem        | c_problem_1        | events                |
| problem        | c_problem_2        | events                |
+----------------+--------------------+-----------------------+

查看表结构：

show create table event_tagG
*************************** 1. row ***************************
       Table: event_tag
Create Table: CREATE TABLE `event_tag` (
  `eventtagid` bigint(20) unsigned NOT NULL,
  `eventid` bigint(20) unsigned NOT NULL,
  `tag` varchar(255) NOT NULL DEFAULT ‘‘,
  `value` varchar(255) NOT NULL DEFAULT ‘‘,
  PRIMARY KEY (`eventtagid`),
  KEY `event_tag_1` (`eventid`),
  CONSTRAINT `c_event_tag_1` FOREIGN KEY (`eventid`) REFERENCES `events_bak20190225` (`eventid`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8

修改外键约束：

alter table event_tag drop FOREIGN KEY  c_event_tag_1;
alter table event_tag add FOREIGN KEY  c_event_tag_1 (`eventid`) REFERENCES `events`(`eventid`) ON DELETE CASCADE;

zabbix好多外键，下次清理数据直接删除吧。