Why
Previous versions created single-column UNIQUE constraints (`models.model_name`, `vendors.name`).
After introducing composite indexes on `(model_name, deleted_at)` and `(name, deleted_at)` for soft-delete support, those legacy constraints could still exist in user databases.
When a record was soft-deleted and re-inserted with the same name, MySQL raised `Error 1062 … for key 'models.model_name'`.
What
• In `migrateDB` and `migrateDBFast` paths of `model/main.go`, proactively drop:
– `models.uk_model_name` and fallback `models.model_name`
– `vendors.uk_vendor_name` and fallback `vendors.name`
• Keeps existing helper `dropIndexIfExists` to ensure the operation is MySQL-only and error-free when indexes are already absent.
Result
Startup migration now removes every possible legacy UNIQUE index, ensuring composite index strategy works correctly.
Users can soft-delete and recreate models/vendors with identical names without hitting duplicate-entry errors.
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