intermediate~4h
Isolation Levels — Dirty Read, Phantom Read, Non-Repeatable Read
Transaction isolation levels control how much a transaction is isolated from the effects of other concurrent transactions. There is a fundamental trade-off: higher isolation = fewer anomalies + more l
Learning objectives
- Define dirty read, non-repeatable read, and phantom read, each with a concrete two-transaction example.
- Rank the four standard isolation levels and state which anomalies each one prevents.
- Explain why PostgreSQL's default Read Committed level never actually permits a dirty read, unlike the SQL standard's baseline.
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Isolation Levels — Dirty Read, Phantom Read, Non-Repeatable Read