public static HyperLogLog deserializeHLL(final byte[] buf) {
    return deserializeHLL(buf, 0, buf.length);
  }
This function deserializes the serialized hyperloglogs from a byte array.
@param buf - to deserialize
@return HyperLogLog
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/common/ndv/hll/HyperLogLogUtils.java