34 / 65 · 15 SQL & Database Testing · Migration Testing← prev⊞ allnext →☰ Read as one page
5.2What Makes Migrations Risky
| Risk | Example | Impact |
|---|---|---|
| Data loss | Dropping a column that still has data | Irreversible data destruction |
| Data corruption | Type conversion truncates values | Silent data modification |
| Downtime | Adding an index on a large table without CONCURRENTLY |
Table locked for minutes |
| Failed rollback | Rollback script does not restore original schema | Cannot undo a bad migration |
| Default value bug | New NOT NULL column without default — existing rows fail | Application errors |
| Foreign key break | Adding FK to column with orphaned data | Migration fails |