Fixing bad production data safely

Added 2026-10-28

Fixing bad production data safely — Chinese original prompt

你是做过多次线上数据订正的资深后端。我要修一批错数据：表 [库表名]，错误判定是 [判定条件]，正确值来自 [来源：另一张表/规则/人工清单]，预计影响 [预计行数范围]，库是 [MySQL/PostgreSQL]。按顺序给：1）圈范围的 SELECT，覆盖边界、NULL 和软删除标记；2）备份表或快照语句；3）分批 UPDATE，每批 [每批行数] 行，显式事务，并说明先在哪套库试跑；4）修后校验三条查询：总数、抽样 [抽样条数] 条、关联表一致性；5）回滚语句，以及什么情况下必须回滚。每条 SQL 都要能直接执行，UPDATE 一律带 WHERE，不许在一个事务里夹带其他改动。最后单列不可逆步骤和需要提前打招呼的人。

Site original

Chinese original

Replace these placeholders 7

Swap the bracketed parts for your own details before sending.

[库表名]
[判定条件]
[来源：另一张表/规则/人工清单]
[预计行数范围]
[MySQL/PostgreSQL]
[每批行数]
[抽样条数]

How to use

改之前先在只读库把 SELECT 跑一遍，行数超预期就停下来。

Try tweaking it

Have it restate requirements and constraints before writing code.
Ask for the smallest change plus a rollback path, not a full-file rewrite.

What you should get

A minimal, runnable change with copy-ready code
Impact list: which files and call sites must follow

Common mistakes

Asking it to touch ten files at once, then losing track of what broke what.
Pasting only the error, with no code or version, and getting an unfixable answer.

How to check the output

The change runs, can be rolled back, and touches nothing unrelated.
Edge cases (empty, oversized, concurrent) are covered or explained.

Where it works

Good for: having it restate requirements and constraints, then propose the smallest runnable change.
Watch out: include versions and a minimal reproduction with the error, or the fix may look plausible but not fit.