@Override
          public Object process(Node nd, Stack<Node> stack, NodeProcessorCtx procCtx,
              Object... nodeOutputs) {
            tableScans.add((TableScanOperator) nd);
            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