@Override
      public Object process(Node nd, Stack<Node> stack, NodeProcessorCtx procCtx,
          Object... nodeOutputs) throws SemanticException {
        return null;
      }
SerializeFilter is a simple physical optimizer that serializes all filter expressions in
Tablescan Operators.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/physical/SerializeFilter.java