Apply migrations only to the disposable copy

Stage 2 of 4. Run the supplied SQL on a disposable in-memory copy.

Build the mechanism

ALTER TABLE attendees ADD COLUMN city TEXT changes the copy. Reading the original file afterward still returns its original schema and rows.

Change the controls, predict the intermediate result, and compare it with the computed evidence. The visual explains this stage; grading executes your Python functions.

Exact contract

Implement rehearse(source,migration), retaining evidence even when a multi-statement script partially succeeds and then errors.

Read API.md, including return fields and failure behavior. The first starter supplies file I/O and HTML presentation; implement the domain functions in main.py. Keep earlier functions passing because later stages compose them.

Verify it

python3 scripts/project_test.py database-migration-rehearsal --stage 2 --path learning-artifacts/database-migration-rehearsal --strict

The stage tests include held-out inputs independent of the demo, boundaries, malformed data and an adversarial case. Inspect the failing assertion before changing a rule.

Failure boundary and extension

ATTACH and dangerous PRAGMAs can undermine copy-only behavior. Deny them and extension/file functions. The policy is not an operating-system sandbox.

After all four stages, run python3 cli.py samples/input.json --output my-output inside your learner workspace. Replace the sample path with your own JSON document, inspect the files and feed the exported artifact to the consumer described in the project README.