Code AnalysisHard 60s

Phantom read with range predicate

What anomaly permits double booking?

Starter code

-- SERIALIZABLE expected but engine is REPEATABLE READ (MySQL)
BEGIN;
SELECT COUNT(*) FROM bookings WHERE room=5 AND day='2026-01-01';  -- 0
INSERT INTO bookings(room, day) VALUES (5, '2026-01-01');
COMMIT;   -- allowed; race with another txn

phantom-read isolation-levels mvcc

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