presto-main/src/main/java/io/prestosql/operator/scalar/HyperLogLogFunctions.java/HyperLogLogFunctions/cardinality
class HyperLogLogFunctions:    @ScalarFunction
    @Description("compute the cardinality of a HyperLogLog instance")
    @SqlType(StandardTypes.BIGINT)
    public static long cardinality(@SqlType(StandardTypes.HYPER_LOG_LOG) Slice serializedHll)
    {
        return HyperLogLog.newInstance(serializedHll).cardinality();
    }