Method FlushFinal

cpp/src/arrow/compute/kernels/vector_hash.cc:421–421

  Status Flush(ExecResult* out) override { return action_.Flush(out); }
  Status FlushFinal(ExecResult* out) override { return action_.FlushFinal(out); }

  Status GetDictionary(std::shared_ptr<ArrayData>* out) override {
    std::shared_ptr<NullArray> null_array;