Question

如何在不事先掌握所有指标的情况下计算以下指标的总和？我可以使用聚合框架或MapReduce完成此操作吗？

[
  {
   player_id: '123',
   timestamp: <sometime>,
   metrics: {
     points_per_game: 1,
     rebounds_per_game: 2,
     assist_per_game: 3,
   }
  },
  {
    player_id: '123',
    timestamp: <sometime>,
    metrics: {
      points_per_game: 1,
      rebounds_per_game: 2,
    }
  },
  {
    player_id: '345',
    timestamp: <sometime>,
    metrics: {
      points_per_game: 1,
      rebounds_per_game: 2,
      point_in_the_paint_per_game: 2
    }
  }
]

我希望得到以下结果

[
 {
   player_id: '123',
   metrics: {
     points_per_game: 2,
     rebounds_per_game: 4,
     assist_per_game: 3,
   }
 },
 {
   player_id: '345',
   metrics: {
     points_per_game: 1,
     rebounds_per_game: 2,
     point_in_the_paint_per_game: 2
   }
 }
]

我无法执行以下操作，因为这将要求我了解每个指标：

db.stats.aggregate([
   {$group: {
     _id: {player: "$player_id"},
     points_per_game: { $sum: "$metrics.points_per_game"}
     ...
])

Answer 1

您可以尝试以下汇总。

将对象转换为键值对的数组，然后将$ unwind + $ group转换为按每个键分组并累加计数。最后一步回到命名键值对象。

wrap

MongoDB汇总字段而无需事先知道所有字段

1 个答案: