public RelNode align(RelNode root) {
    final RelNode newRoot = dispatchAlign(root, ImmutableList.<RelFieldCollation>of());
    return newRoot;
  }
Execute the logic in this class. In particular, make a top-down traversal of the tree
and annotate and recreate appropriate operators.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelColumnsAlignment.java