5602. Online Schema Changes: expand-contract migration — Implement the workflow with safe SQL and application handling. — messaging — Python + FastAPI + SQLAlchemy

DBMS Published 30 Sept 2026 Updated 30 Sept 2026 0 Views Verified

Scenario: A messaging application must handle expand-contract migration. Implement the workflow with safe SQL and application handling. Explain the invariant, SQL strategy, transaction/locking behavior, failure handling, observability and test plan. Use MySQL 8-oriented syntax where applicable.

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Answer & Explanation

4 Answers

Verified

Option 1: Disable database protections and repair inconsistent rows manually after expand-

Disable database protections and repair inconsistent rows manually after expand-contract migration runs.

Additional Explanation

Correctness depends on explicit invariants, safe SQL, transaction/concurrency handling and verification.

Verified

Option 2: Run expand-contract migration without defining transaction boundaries, retry beh

Run expand-contract migration without defining transaction boundaries, retry behavior, or production validation.

Additional Explanation

Correctness depends on explicit invariants, safe SQL, transaction/concurrency handling and verification.

Verified Correct Answer

Option 3: Use a parameterized, transaction-aware MySQL 8 implementation for expand-contrac

Use a parameterized, transaction-aware MySQL 8 implementation for expand-contract migration, validate the invariant, and explicitly test concurrency, retries and recovery.

Additional Explanation

Correctness depends on explicit invariants, safe SQL, transaction/concurrency handling and verification.

Verified

Option 4: Use unparameterized dynamic SQL and rely only on application-side validation for

Use unparameterized dynamic SQL and rely only on application-side validation for expand-contract migration.

Additional Explanation

Correctness depends on explicit invariants, safe SQL, transaction/concurrency handling and verification.