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Transaction isolation levels in Postgres — what anomalies does each level prevent?

Q: Transaction isolation levels in Postgres — what anomalies does each level prevent?

Postgres has 3 levels (Read Uncommitted ≡ Read Committed). `READ COMMITTED` = per-statement snapshot. `REPEATABLE READ` = txn snapshot, no non-repeatable reads. `SERIALIZABLE` (SSI) = no phantoms/write-skew but aborts on serialization failures — retry required. Isolation levels: anomalies blocked vs concurrency — Postgres defaults to READ COMMITTED Read Committed sees committed rows only allows non-repeatable read phantom reads allowed default in Postgres</te

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Map Read Committed / Repeatable Read / Serializable to dirty reads, non-repeatable reads, and phantoms.

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Postgres has 3 levels (Read Uncommitted ≡ Read Committed). READ COMMITTED = per-statement snapshot. REPEATABLE READ = txn snapshot, no non-repeatable reads. SERIALIZABLE (SSI) = no phantoms/write-skew but aborts on serialization failures — retry required.

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