@Override
    public Object process(Node nd, Stack<Node> stack, NodeProcessorCtx ctx,
        Object... nodeOutputs) throws SemanticException {
      super.process(nd, stack, ctx, nodeOutputs);
      List<FieldNode> cols = ((ColumnPrunerProcCtx) ctx).getPrunedColLists().get(nd);
      if (null != cols) {
        pruneOperator(ctx, (LimitOperator) nd, cols);
      }
      return null;
    }
Factory method to get the ColumnPrunerGroupByProc class.

@return ColumnPrunerGroupByProc
ql/src/java/org/apache/hadoop/hive/ql/optimizer/ColumnPrunerProcFactory.java