This is postgres-style query execution "above" hdfs/hadoop style storage.

Hadapt is hadoop-style job execution "above" postgres-style storage.

Is that really accurate? I had perceived things as the other way around, as Hadapt has a mixed storage model and CitusDB uses external tables for everything...

Especially given that Redshift, Greenplum and Aster directly build on or incorporate technology from PostgreSQL.

This is true for Vertica as well.