I’m implementing a Stackoverflow-like reputation system on my rap lyrics explanation site, Rap Genius:
- Good explanation: +10
- Bad explanation: -1
- Have the most explanations on a song: +30
My question is how to implement this. Specifically, I’m trying to decide whether I should create a table of reputation_events to aid in reputation re-calculation, or whether I should just recalculate from scratch whenever I need to.
The table of reputation_events would have columns for:
- name (e.g., “good_explanation”, “bad_explanation”)
- awarded_to_id
- awarded_by_id
- awarded_at
Whenever something happens that affects reputation, I insert a corresponding row into reputation_events. This makes it easy to recalculate reputation and to generate a human-readable sequence of events that generated a given person’s reputation.
On the other hand, any given action could affect multiple user’s reputation. E.g., suppose user A overtakes user B on a given song; based on the “Have the most explanations on a song” goal, I would have to remember to delete B’s original “has_the_most_explanations” event (or maybe I would add a new event for B?)
In general, I never like data to exist in more than one place. It sounds like your “reputation_events” table would contain data that can be calculated from other data. If so, I’d recalculate from scratch, unless the performance impact becomes a real problem.
When you have calculated data stored, you have the possibility that it may not correspond correctly with the base data — basically a corrupted state. Why even make it possible if you can avoid it?