@Override
  public String toString() {
    return "PollFilePayload{commitContext="
        + commitContext
        + ", writingOffset="
        + writingOffset
        + "}";
  }
The offset from which the file content should be read.
iotdb-client/service-rpc/src/main/java/org/apache/iotdb/rpc/subscription/payload/poll/PollFilePayload.java