presto-rcfile/src/main/java/io/prestosql/rcfile/text/DecimalEncoding.java/DecimalEncoding/parseSlice
class DecimalEncoding:    private Slice parseSlice(Slice slice, int offset, int length)
    {
        BigDecimal decimal = parseBigDecimal(slice, offset, length);
        return encodeUnscaledValue(decimal.unscaledValue());
    }