Need help optimizing a google apps script that labels emails

Question

Gmail has a issue where conversation labels are not applied to new messages that arrive in the conversation thread. issue details here

We found a Google Apps Script

Answer 1

This will find individual messages that do not have a label and apply the label of the associated thread. It takes much less time because it's not relabeling every single message.

function label_unlabeled_messages() {
  var unlabeled = GmailApp.search("has:nouserlabels -label:inbox -label:sent -label:chats -label:draft -label:spam -label:trash");

  for (var i = 0; i < unlabeled.length; i++) {
    Logger.log("thread: " + i + " " + unlabeled[i].getFirstMessageSubject());
    labels = unlabeled[i].getLabels();
    for (var j = 0; j < labels.length; j++) {
      Logger.log("labels: " + i + " " + labels[j].getName());
      labels[j].addToThread(unlabeled[i]);
    }
  }
}