Convert field object to array of objects with a query for existing documents

Question

I have an array of lessons that contain supplementalLessonVideo, which is an object. I want to now make the field instead be an array called supplementalLessonVideos and move the object from supplementalLessonVideo into the first index with a query. Not all lessons contain the field either, only some.

Schema:

...
lessons: [
  {
    supplementalLessonVideo: 
      {
        videoId: { type: Schema.Types.ObjectId, ref: "Video" },
        _id: { type: Schema.Types.ObjectId },
        fieldname: { type: String },
        originalname: { type: String },
        encoding: { type: String },
        mimetype: { type: String },
        filename: { type: String },
        size: { type: Number },
        key: { type: String },
        url: { type: String },
      },
  },
];

and I am wanting to make it into:

...
lessons:[
    {
 supplementalLessonVideos: 
        [
      {
          videoId: { type: Schema.Types.ObjectId, ref: "Video" },
          _id: { type: Schema.Types.ObjectId },
          fieldname: { type: String },
          originalname: { type: String },
          encoding: { type: String },
          mimetype: { type: String },
          filename: { type: String },
          size: { type: Number },
          key: { type: String },
          url: { type: String },
       }
        ]
    }
]

Is there a query I can write and run on the DB to convert the field to an array and then move the object data into the first index of the array?

So, going from this:

    "supplementalLessonVideo" : {
                "videoId" : ObjectId("5ed868ab7c77482170d135f3"), 
                "_id" : ObjectId("5ed868ab7c77482170d135f4"), 
                "fieldname" : "supplemental-lesson-video", 
                "originalname" : "Student Navigation Video April 2018.mp4", 
                "encoding" : "7bit", 
                "mimetype" : "video/mp4", 
                "filename" : "supplemental-lesson-video-1591240848919-741719000", 
                "size" : 15255388, 
                "key" : "supplemental-lesson-video", 
                "url" : "https://vimeo.com"
            },

To this:

    "supplementalLessonVideos" : [{
                "videoId" : ObjectId("5ed868ab7c77482170d135f3"), 
                "_id" : ObjectId("5ed868ab7c77482170d135f4"), 
                "fieldname" : "supplemental-lesson-video", 
                "originalname" : "Student Navigation Video April 2018.mp4", 
                "encoding" : "7bit", 
                "mimetype" : "video/mp4", 
                "filename" : "supplemental-lesson-video-1591240848919-741719000", 
                "size" : 15255388, 
                "key" : "supplemental-lesson-video", 
                "url" : "https://vimeo.com"
            }],

Gibbs · Accepted Answer · 2020-07-24 19:28:21Z

1

You can use. It creates an array and deletes the older object.

db.getCollection('test2').update({},[{
    $set: {
            supplementalLessonVideos: {
                $concatArrays: [
                    [], //Creating new array
                    [{ //Adding values from object
                        videoId:"supplementalLessonVideo.videoId",
                        encoding:"supplementalLessonVideo.encoding"                    
                    }]
                ]
                }}          
},

{
    $unset:"supplementalLessonVideo"
}])

updateMany also works in this case.

answered Jul 24, 2020 at 19:28

Gibbs

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