presto-main/src/main/java/io/prestosql/type/CharOperators.java/CharOperators/indeterminate
class CharOperators:    @LiteralParameters("x")
    @ScalarOperator(INDETERMINATE)
    @SqlType(StandardTypes.BOOLEAN)
    public static boolean indeterminate(@SqlType("char(x)") Slice value, @IsNull boolean isNull)
    {
        return isNull;
    }