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Multiversion Concurrency Control

Snapshot Isolation

Write skew

• Postgres REPEATABLE READ behavior not serializable.

• T1 < T2: (1, 300), (2, 500).

• T2 < T1: (1, 400), (2, 300).

• Result (snapshot isolation): (1, 300), (1, 300).

• S2PL would have prevented this.

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