给业务添加唯一索引之前,必须核对当前的数据是否违反唯一索引约束:
检测:
select count( distinct app_id,count_date,cluster,priority) from events ; select count( *) from events ; select app_id,count_date,cluster,priority ,count(*) from events group by app_id,count_date,cluster,priority having count(*) >1 limit 20;
违反约束:
alter table events add unique index uk_app(app_id,count_date,cluster,priority);
ERROR 1062 (23000): Duplicate entry '2882303761517233197-2020-09-21-ALL-1' for key 'uk_id'