Aggregation to show avg_mtc for individual directors

MongoDB University M121: The MongoDB Aggregation Framework
#1

I’m trying to fashion an aggregation that’ll tell me which director in the movies database has the highest average metecritic score. Here is what I have so far:

dirAgg=[
  {
    $group: { 
      _id: "$directors",
      num_films_directed: { $sum: 1 },
      avg_mtc: { $avg: "$metacritic" }
    }
  },
  {
    $sort: { "avg_mtc": -1 }
  }
]

The problem is that directors is an array field. I’ve been trying to fashion an aggregation that’ll group the documents by individual director - but the only solution I can think of is re-doing the entire movies collection so each movie has duplicate documents for each director with only one director name in the field (e.g. “Fargo” would have two entries, one for Joel Coen and one for Ethan Coen).

There has to be a better way than that, but I’m having trouble wrapping my head around it.

#2

You’ll most likely want to $unwind the array.