message: Issue Serial Positional Join
  It's not a parallel sink...
diff: @@ -42,9 +42,6 @@ public:
  bool IsSink() const override {
  return true;
  }
  - bool ParallelSink() const override {
  - return true;
  - }
  public:
  void BuildPipelines(Pipeline &current, MetaPipeline &meta_pipeline) override;
  