@Override
    public Object process(Node nd, Stack<Node> stack, NodeProcessorCtx procCtx,
        Object... nodeOutputs) throws SemanticException {
      // do nothing
      return null;
    }
Fixed bucket pruning optimizer goes through all the table scans and annotates them
with a bucketing inclusion bit-set.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/FixedBucketPruningOptimizer.java