@Override
  public RelNode accept(RelShuttle shuttle) {
    if(shuttle instanceof HiveRelShuttle) {
      return ((HiveRelShuttle)shuttle).visit(this);
    }
    return shuttle.visit(this);
  }
Copy TableScan operator with a new Row Schema. The new Row Schema can only
be a subset of this TS schema. Copies underlying RelOptHiveTable object
too.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/reloperators/HiveTableScan.java