When smurph proposed the deltas table I was worried about the recompute load to keep it up to date.
But actually, I just realised that there must be a process every “so often” (is it 15 days) where a big recompute is done, and that’s where the ranks change. So it would be natural to update the delta table at that time - basically for free - and we all could live happily ever after!
@anoek, is this sound, in principle?
I was thinking you’d just compute all of the deltas whenever a user requested the table. Grab the ratings of everyone that fits on the table, which is already done, and retroactively compute the deltas based on the user’s current rating. All of the computation could be done on demand on the client, with the server just returning a column of opponent Glicko ratings in addition to the user names, game results, and user rankings that it already returns.
Alternately, just include the ranking adjustments in the deltas. That way, someone can look at the table, see that they won a game, but their ranking went down, and understand that it happened because the rankings were adjusted. The ranking graph doesn’t appear to update historic ratings based on rank changes for other players, so if the goal is to match the deltas to the ranking graph, including the adjustments might be a good idea.