postgres isolation level - ghdrako/doc_snipets GitHub Wiki

Isolation level	Dirty read	Nonrepeatable read	Phantom read	Serialization anomaly
Read uncommitted	YES	NO	NO	NO
Read committed	YES	NO	NO	NO
Repeatable read	YES	YES	YES	NO
Serializable	YES	YES	YES	YES

In PostgreSQL the read uncommitted isolation level behaves the same as the read committed, which is the default mode.