presto-main/src/main/java/io/prestosql/sql/analyzer/StatementAnalyzer.java/Visitor/visitExcept
class Visitor:        @Override
        protected Scope visitExcept(Except node, Optional<Scope> scope)
        {
            if (!node.isDistinct()) {
                throw semanticException(NOT_SUPPORTED, node, "EXCEPT ALL not yet implemented");
            }

            return visitSetOperation(node, scope);
        }