presto-main/src/main/java/io/prestosql/operator/scalar/StringFunctions.java/StringFunctions/charUpper
class StringFunctions:    @Description("converts the string to upper case")
    @ScalarFunction("upper")
    @LiteralParameters("x")
    @SqlType("char(x)")
    public static Slice charUpper(@SqlType("char(x)") Slice slice)
    {
        return upper(slice);
    }