title: Order a ParseQuery by the date at which only one field has been updated
body: <p>I have a feed containing posts that are currently ordered by "updatedAt". My original intention was to push up posts to the top of the feed which were last replied to (I do this by incrementing a "replyCount" field in each post when a user leaves a comment), not totally cognizant of the fact that another field, "likeCount" is also being updated when user's "like" a post. I would still like to push those posts that were recently "replied to" to the top of the feed, but do not at the expense of the weird UX behavior that associated with liking posts pushing them up as well. I'm not sure how to separate the two.</p>
  
  <p>What should I do here? Can I maybe add another column called "lastReplyCountTime" and then sort queries based on that? Maybe set lastReplyCountTime for all posts to the current time when saved to the database, and then only update that value when a post receives a reply?</p>
  
  <pre><code>        String groupId = ParseUser.getCurrentUser().getString("groupId");
          ParseQuery&lt;ParseObject&gt; query = new ParseQuery&lt;&gt;(ParseConstants.CLASS_POST);
          query.whereContains(ParseConstants.KEY_GROUP_ID, groupId);
          /*query.addDescendingOrder(ParseConstants.KEY_CREATED_AT);*/
          query.orderByDescending("updatedAt");
          query.findInBackground((posts, e) -&gt; {
  
              if (mSwipeRefreshLayout.isRefreshing()) {
                  mSwipeRefreshLayout.setRefreshing(false);
              }
  
              if (e == null) {
  
                  // We found messages!
                  mPosts = posts;
  
                  String[] usernames;
                  usernames = new String[mPosts.size()];
                  int i = 0;
                  for(ParseObject post : mPosts) {
                      usernames[i] = yeet.getString(ParseConstants.KEY_SENDER_NAME);
                      i++;
                  }
  
                  FeedAdapter adapter = new FeedAdapter(
                          getListView().getContext(),
                          mYeets);
                  setListAdapter(adapter);
  
              }
          });
      }
  </code></pre>