Ah, in my worldview those steps are still in a single transaction. It's just formulated as several ordered statements. Is that mechanism unique to PostgreSQL?

Ah, in my worldview those steps are still in a single transaction. It's just formulated as several ordered statements. Is that mechanism unique to PostgreSQL? Or is it just that this transaction is impractical for you, due to the wall clock duration and how it impacts other use of the DB?