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

            return new FilterNode(node.getId(), source, canonicalize(node.getPredicate()));
        }