获取聚合中嵌套数组的总和 [英] Get sum of Nested Array in Aggregate

问题描述

好的，我有一个似乎无法解决的问题.

Ok, I have an issue I cannot seem to solve.

我有一个这样的文件:

{
  "playerId": "43345jhiuy3498jh4358yu345j",
  "leaderboardId": "5b165ca15399c020e3f17a75",
  "data": {
    "type": "EclecticData",
    "holeScores": [
      {
        "type": "RoundHoleData",
        "xtraStrokes": 0,
        "strokes": 3,
      },
      {
        "type": "RoundHoleData",
        "xtraStrokes": 1,
        "strokes": 5,
      },
      {
        "type": "RoundHoleData",
        "xtraStrokes": 0,
        "strokes": 4
      }
    ]
  }
}

现在，我要完成的工作是使用笔画的总和，然后再对其进行排序.我正在尝试:

Now, what I am trying to accomplish is using aggregate sum the strokes and then order it afterwards. I am trying this:

var sortedBoard = db.collection.aggregate(
    {$match: {"leaderboardId": boardId}},
    {$group: {
        _id: "$playerId",
        played: { $sum: 1 },
        strokes: {$sum: '$data.holeScores.strokes'}
        }
    },
    {$project:{ 
        type: "$SortBoard",
        avgPoints: '$played',
        sumPoints: "$strokes",
        played : '$played'
    }}
);

这里的问题是我确实获得了正确的笔画总和，因为它在另一个数组中.

The issue here is that I do net get the strokes sum correct, since this is inside another array.

希望有人可以帮助我，在此先感谢:-)

Hope someone can help me with this and thanks in advance :-)

推荐答案

您需要说

原因是因为您同时使用它两者作为求和数组值"的方式，也用作

The reason is because you are using it both as a way to "sum array values" and also as an "accumulator" for $group.

您似乎遗漏的另一件事是 $group 仅输出您告诉它的字段，因此，如果要访问其他阶段的其他字段或输出，则需要使用

The other thing you appear to be missing is that $group only outputs the fields you tell it to, therefore if you want to access other fields in other stages or output, you need to keep them with something like $first or another accumulator. We also appear to be missing a pipeline stage in the question anyway, but it's worth noting just to be sure.

还请注意，您确实应该将聚合管道包装为官方数组[]，因为不赞成使用旧版用法，并且在某些语言实现中可能会引起问题.

Also note you really should wrap aggregation pipelines as an official array [], because the legacy usage is deprecated and can cause problems in some language implementations.

返回正确的课程详细信息:

Returns the correct details of course:

{
        "_id" : "43345jhiuy3498jh4358yu345j",
        "avgPoints" : 1,
        "sumPoints" : 12,
        "played" : 1
}

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