| 语句 | ALTER TABLE t UPDATE col = expr WHERE cond；ALTER TABLE t DELETE WHERE cond |
|---|---|
| 状态表 | system.mutations 的 is_done、parts_to_do、latest_fail_reason |
| 运维语句 | KILL MUTATION WHERE …；SYSTEM STOP MERGES 暂停合并影响进度 |
示例
示例
ALTER TABLE events UPDATE level = 0 WHERE level < 0;
SELECT command, is_done, parts_to_do, latest_fail_reason
FROM system.mutations
WHERE table = 'events' AND NOT is_done;
-- 清理失败任务
-- KILL MUTATION WHERE database = 'analytics' AND table = 'events';mutation 是重写操作，高频 UPDATE/DELETE 与 ClickHouse 的定位相悖；适合场景是修正少量脏数据与批量删除历史。