presto-main/src/main/java/io/prestosql/operator/scalar/DataSizeFunctions.java/Unit/parse
class Unit:        public static Unit parse(String unitString, String dataSize)
        {
            switch (unitString) {
                case "B":
                    return BYTE;
                case "kB":
                    return KILOBYTE;
                case "MB":
                    return MEGABYTE;
                case "GB":
                    return GIGABYTE;
                case "TB":
                    return TERABYTE;
                case "PB":
                    return PETABYTE;
                case "EB":
                    return EXABYTE;
                case "ZB":
                    return ZETTABYTE;
                case "YB":
                    return YOTTABYTE;
                default:
                    throw invalidDataSize(dataSize);
            }
        }