6508:20160604:144112.323 query [txnlev:1] [begin;]
  6508:20160604:144112.323 query [txnlev:1] [alter table event_tag add constraint c_event_tag_1 foreign key (eventid) references events (eventid) on delete cascade]
  6508:20160604:144112.384 [Z3005] query failed: [1005] Can't create table `zabbix`.`#sql-83a_f15c` (errno: 150 "Foreign key constraint is incorrectly formed") [alter table event_tag add constraint c_event_tag_1 foreign key (eventid) references events (eventid) on delete cascade]
  6508:20160604:144112.384 query [alter table event_tag add constraint c_event_tag_1 foreign key (eventid) references events (eventid) on delete cascade] failed, setting transaction as failed
  6508:20160604:144112.384 query [txnlev:1] [rollback;]
  6508:20160604:144112.384 database upgrade failed