@Override
  public boolean isSame(Object o) {
    if (o instanceof ExprNodeColumnListDesc) {
      return columns.equals(((ExprNodeColumnListDesc)o).columns);
    }
    return false;
  }
Dummy desc only for populating TOK_ALLCOLREF and should not be used
outside of TypeCheckProcFactory
ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeColumnListDesc.java