MongoDB：在深度嵌套的对象数组中进行聚合查找

Question

我有两个收藏：

音频

[
       {
        "_id": "5f6b1a2e69eef14818ca03a7",
        "audioURL": "https://boyd.org",
        "state": "draft",
       }
       {
        "_id": "5f6b1e1c6297f34bc6f1fee3",
        "name": "navigate",
        "audioURL": "http://mariane.org",
        "state": "draft",
       },
       {
        "_id": "5f5b5423ba39f738d593b504",
        "audioURL": "https://storage/test123mp31599820832928.mp3",
        "state": "draft",
       }
]

课程：

 "lessons": [
  {
   "_id": "5f770e275cef7a611f3cf931",
   "minigameDescriptions": [
    {
     "assessmentSections": [
      {
       "mark": "step_1",
       "start": 1,
       "end": 2,
       "stepAudio": {
        "backingTrackAudioId": "5f6b1a2e69eef14818ca03a7",
        "previewTrackAudioId": "5f6b1a2e69eef14818ca03a7"
       }
      },
      {
       "mark": "step_2",
       "start": 3,
       "end": 6,
       "stepAudio": {
        "backingTrackAudioId": "5f6b1e1c6297f34bc6f1fee3",
        "previewTrackAudioId": "5f6b1e1c6297f34bc6f1fee3"
       }
      },
      {
       "mark": "step_3",
       "start": 7,
       "end": 10,
       "stepAudio": {
        "backingTrackAudioId": "5f6b1a2e69eef14818ca03a7",
        "previewTrackAudioId": "5f5b5423ba39f738d593b504"
       }
      }
     ],
     "drumStyleName": "DrumStyleHalftimeShuffle",
     "onboarding": false,
     "showHints": false,
     "minigameType": "StrummingTrainer",
    }
   ],
   "_updated_at": "2020-10-02T12:00:23.848Z",
  }
 ]
}

现在我必须汇总它，因为在每个 mingameDescriptions.assessmentSections 中都有属性 stepAudio 具有 previewTrackAudioId 和 backingTrackAudioId。这些对集合“音频”的引用，我需要将它们作为对象加入其中（音频主键是_id）。我已经尝试过以下管道（现在我只尝试查找 previewTrackAudio ）：

{
        $unwind: {
          path: "$minigameDescriptions.assessmentSections",
          preserveNullAndEmptyArrays: true
        },
      },
      {
        $lookup: {
          from: "audios",
          let: {
            audioId: "$minigameDescriptions.assessmentSections.stepAudio.previewTrackAudioId"
          },
          pipeline: [
            {
              $match: {
                $expr: {
                  $eq: ["$_id", "$$audioId"]
                }
              }
            }
          ],
          as: "minigameDescriptions.assessmentSections.stepAudio.previewTrackAudio"
        }
      },
      {
        $unwind: {
          preserveNullAndEmptyArrays: true,
          path: "$minigameDescriptions.assessmentSections.stepAudio.previewTrackAudio"
        }
      }

它“有点”有效，我得到以下结果：

{
 "lessons": [
  {
   "_id": "5f770e275cef7a611f3cf931",
   "minigameDescriptions": [
    {
     "assessmentSections": {
      "mark": "step_2",
      "start": 3,
      "end": 6,
      "stepAudio": {
       "backingTrackAudioId": "5f6b1e1c6297f34bc6f1fee3",
       "previewTrackAudioId": "5f6b1e1c6297f34bc6f1fee3",
       "previewTrackAudio": {
        "_id": "5f6b1e1c6297f34bc6f1fee3",
        "name": "navigate",
        "audioURL": "http://mariane.org",
        "state": "draft",
       }
      }
     },
     "drumStyleName": "DrumStyleHalftimeShuffle",
     "onboarding": false,
     "showHints": false,
     "minigameType": "StrummingTrainer",
    },
    {
     "assessmentSections": {
      "mark": "step_3",
      "start": 7,
      "end": 10,
      "stepAudio": {
       "backingTrackAudioId": "5f6b1a2e69eef14818ca03a7",
       "previewTrackAudioId": "5f5b5423ba39f738d593b504",
       "previewTrackAudio": {
        "_id": "5f5b5423ba39f738d593b504",
        "audioURL": "https://storage/test123mp31599820832928.mp3",
        "state": "draft",
       }
      }
     },
     "drumStyleName": "DrumStyleHalftimeShuffle",
     "onboarding": false,
     "showHints": false,
     "minigameType": "StrummingTrainer",
    },
    {
     "assessmentSections": {
      "mark": "step_1",
      "start": 1,
      "end": 2,
      "stepAudio": {
       "backingTrackAudioId": "5f6b1a2e69eef14818ca03a7",
       "previewTrackAudioId": "5f6b1a2e69eef14818ca03a7",
       "previewTrackAudio": {
        "_id": "5f6b1a2e69eef14818ca03a7",
        "audioURL": "https://boyd.org",
        "state": "draft",
       }
      }
     },
     "drumStyleName": "DrumStyleHalftimeShuffle",
     "onboarding": false,
     "showHints": false,
     "minigameType": "StrummingTrainer",
    }
   ],
   "_updated_at": "2020-10-02T12:00:23.848Z",
  }
 ]
}

但是现在我没有一个包含 3 个 mingameDescriptions.assessmentSections 的数组，而是一个包含三个对象的数组，这些对象具有 assesmentSections 以及来自 minigameDescriptions 的重复属性，这是错误的：/。我该如何解决这个问题？

我想得到的是：

 "lessons": [
  {
   "_id": "5f770e275cef7a611f3cf931",
   "minigameDescriptions": [
    {
     "assessmentSections": [
      {
       "mark": "step_1",
       "start": 1,
       "end": 2,
       "stepAudio": {
        "backingTrackAudioId": "5f6b1a2e69eef14818ca03a7",
        "previewTrackAudioId": "5f6b1a2e69eef14818ca03a7",
        "previewTrackAudio": {
         "_id": "5f6b1a2e69eef14818ca03a7",
         "audioURL": "https://boyd.org",
         "state": "draft",
        }
       }
      },
      {
       "mark": "step_2",
       "start": 3,
       "end": 6,
       "stepAudio": {
        "backingTrackAudioId": "5f6b1e1c6297f34bc6f1fee3",
        "previewTrackAudioId": "5f6b1e1c6297f34bc6f1fee3",
        "previewTrackAudio": {
          "_id": "5f5b5423ba39f738d593b504",
          "audioURL": "https://storage/test123mp31599820832928.mp3",
          "state": "draft",
         }
       }
      },
      {
       "mark": "step_3",
       "start": 7,
       "end": 10,
       "stepAudio": {
        "backingTrackAudioId": "5f6b1a2e69eef14818ca03a7",
        "previewTrackAudioId": "5f5b5423ba39f738d593b504",
        "previewTrackAudio": {
         "_id": "5f5b5423ba39f738d593b504",
         "audioURL": "https://storage/test123mp31599820832928.mp3",
         "state": "draft",
        }
       }
      }
     ],
     "drumStyleName": "DrumStyleHalftimeShuffle",
     "onboarding": false,
     "showHints": false,
     "minigameType": "StrummingTrainer",
    }
   ],
   "_updated_at": "2020-10-02T12:00:23.848Z",
  }
 ]
}

Answer 1

你的尝试是正确的。

[
  {
    $unwind: "$minigameDescriptions"
  },
  {
    $unwind: "$minigameDescriptions.assessmentSections"
  },
  {
    $lookup: {
      from: "Audios",
      let: {
        audioId: "$minigameDescriptions.assessmentSections.stepAudio.previewTrackAudioId"
      },
      pipeline: [
        {
          $match: {
            $expr: {
              $eq: [
                "$_id",
                "$$audioId"
              ]
            }
          }
        }
      ],
      as: "minigameDescriptions.assessmentSections.stepAudio.previewTrackAudio"
    }
  },
      {
    $group: {
      _id: {
        _id: "$_id",
        /**   assId: "$minigameDescriptions.assessmentSections.mark"*/
        
      },
      assessmentSections: {
        $addToSet: "$minigameDescriptions.assessmentSections"
      },
      drumStyleName: {
        $first: "$minigameDescriptions.drumStyleName"
      },
      minigameType: {
        $first: "$minigameDescriptions.minigameType"
      }
    }
  },
  {
    $group: {
      _id: "$_id",
      minigameDescriptions: {
        $addToSet: {
          assessmentSections: "$assessmentSections",
          drumStyleName: "$drumStyleName",
          minigameType: "$minigameType"
        }
      }
    }
  }
]

工作Mongo playground

注意：这里我们做了两次展开，所以最好进行分组操作。小心，我在第一组中评论了assessmentId，这在您的文档中不存在。但最好有任何东西来识别assessmentSections 中的每个元素，这有助于不复杂