Very cool! pg_duckdb itself is missing fully integrated storage - it can query data stored externally (say in S3) in delta/iceberg formats, but it can't write out data in those formats via transactional writes to PG tables (insert\update\deletes). pg_mooncacke is one neat way of solving that problem. It lets you have a columnstore table in Postgres that can do both reads and writes as if it's any other PG table and have the storage format be an open format like delta/iceberg/etc with that data persisted to blob store (like most cloud DWs would do anyways).