@Override
  public SubscriptionPollPayload deserialize(final ByteBuffer buffer) {
    commitContext = SubscriptionCommitContext.deserialize(buffer);
    offset = ReadWriteIOUtils.readInt(buffer);
    return this;
  }
The index for the next batch of tablets.
iotdb-client/service-rpc/src/main/java/org/apache/iotdb/rpc/subscription/payload/poll/PollTabletsPayload.java