PostgreSQL has what's sometimes called a Volcano-style executor, after a system called Volcano, about which Goetz Greafe published several very interesting papers in the early to mid 1990s. PostgreSQL was in its infancy in those days, but many of the concepts in the Volcano papers have made their way into PostgreSQL over the years. It may also be that Volcano took inspiration from PostgreSQL or its predecessors; I'm not entirely sure of the history or who took inspiration from whom. In any case, the Volcano execution model has been thoroughly embedded in PostgreSQL for the entire history of the database system; the first chinks in the armor only started to appear in 2017.
