- Add migration for UNIQUE index on external_ref column (bd-897a)
- Add validation for duplicate external_ref in batch imports (bd-7315)
- Add query planner test to verify index usage (bd-f9a1)
- Add concurrent import tests for external_ref (bd-3f6a)
The migration detects existing duplicates and fails gracefully.
Batch imports now reject duplicates with clear error messages.
Tests verify the index is actually used by SQLite query planner.
Amp-Thread-ID: https://ampcode.com/threads/T-45ca66ed-3912-46c4-963c-caa7724a9a2f
Co-authored-by: Amp <amp@ampcode.com>
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