DFT: give non-emptiness hints to DSH.
DFT: give non-emptiness hints to DSH.

Former-commit-id: fd59e71a67e39532e81e146dfaa1e4c4e69fc4ae
Former-commit-id: 09242cf37cea161be28f1be9820a6f0e7e2cee5c
ulricha/dsh-aquery