presto-main/src/main/java/io/prestosql/type/HyperLogLogOperators.java/HyperLogLogOperators/castToP4Hll
class HyperLogLogOperators:    @ScalarOperator(CAST)
    @SqlType(StandardTypes.P4_HYPER_LOG_LOG)
    public static Slice castToP4Hll(@SqlType(StandardTypes.HYPER_LOG_LOG) Slice slice)
    {
        HyperLogLog hll = HyperLogLog.newInstance(slice);
        hll.makeDense();
        return hll.serialize();
    }