}
RelDataType newRowType = RexUtil.createStructType(child.getCluster().getTypeFactory(), exprs, origRowType.getFieldNames());
// Insert a top project which allows duplicate columns.
child = new ProjectAllowDupPrel(child.getCluster(), child.getTraitSet(), child, exprs, newRowType);
List<RelNode> children = Lists.newArrayList();
children.add( child);
return (Prel) root.copy(root.getTraitSet(), children);