presto-main/src/main/java/io/prestosql/sql/planner/DomainTranslator.java/DomainTranslator/getSaturatedFloorCastOperator
class DomainTranslator:        private Optional<ResolvedFunction> getSaturatedFloorCastOperator(Type fromType, Type toType)
        {
            try {
                return Optional.of(metadata.getCoercion(SATURATED_FLOOR_CAST, fromType, toType));
            }
            catch (OperatorNotFoundException e) {
                return Optional.empty();
            }
        }