public static long getEstimatedCountFromSerializedHLL(InputStream in) throws IOException {
    checkMagicString(in);
    in.read();
    return readVulong(in);
  }
Get estimated cardinality without deserializing HLL
@param in
         - serialized HLL
@return - cardinality
@throws IOException
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/common/ndv/hll/HyperLogLogUtils.java