presto-main/src/main/java/io/prestosql/sql/planner/optimizations/UnaliasSymbolReferences.java/Rewriter/visitSort
class Rewriter:        @Override
        public PlanNode visitSort(SortNode node, RewriteContext<Void> context)
        {
            PlanNode source = context.rewrite(node.getSource());

            return new SortNode(node.getId(), source, canonicalizeAndDistinct(node.getOrderingScheme()), node.isPartial());
        }