The coursesMarks property is present in every object. So I want to push the value inside coursesMarks property, to an array and return the array to the user.

[
        {
            "coursesMarks": {
                "_id": "634a9be567a1f07be02f71d8",
                "courseCode": "cse1201",
                "courseTitle": "SP"
            }
        },
        {
            "coursesMarks": {
                "_id": "634a9be567a1f07be02f71db",
                "courseCode": "cse1203",
                "courseTitle": "DS"
                
            }
        }
]

Then expected output is:

[
{

     "courses":
                {
                        "_id": "634a9be567a1f07be02f71d8",
                        "courseCode": "cse1201",
                        "courseTitle": "SP"
                },
                {
                        "_id": "634a9be567a1f07be02f71db",
                        "courseCode": "cse1203",
                        "courseTitle": "DS"
                }
    
}
]

CodePudding user response：

I've asked a clarifying question in the comments. But if we assume that the sample data provided is a single document where the array is stored in a field named arr, then a pipeline similar to the following may be what you are looking for:

[
  {
    $addFields: {
      courses: {
        $map: {
          input: "$arr",
          in: "$$this.coursesMarks"
        }
      }
    }
  },
  {
    $unset: "arr"
  }
]

Playground example here

Edit

Based on the additional information about the structure of the data, you are looking to $group things in this particular case. Therefore the relevant addition to your pipeline should look something like this:

[
  ...
  {
    $group: {
      _id: null,
      courses: {
        $push: "$coursesMarks"
      }
    }
  },
  {
    $unset: "_id"
  }
]

Playground demonstration here. It includes an empty $match stage at the beginning to represent whatever additional matching logic you currently have.