Mongo db array of images change schema

I have an array of images in mongodb and I am trying to change the schema of the array. Right now the images are stored like bellow

["https://images.freeimages.com/images/large-previews/e51/tokyo05-2-1447803.jpg","https://images.freeimages.com/images/large-previews/aae/lomo-spider-1386711.jpg","https://images.freeimages.com/images/large-previews/383/the-home-of-the-candle-1-1425911.jpg"]

And the final output I want is like bellow.

[
    {
      url:
        "https://images.freeimages.com/images/large-previews/e51/tokyo05-2-1447803.jpg",
      index: "1"
    },
    {
      url:
        "https://images.freeimages.com/images/large-previews/aae/lomo-spider-1386711.jpg",
      index: "2"
    },
    {
      url:
        "https://images.freeimages.com/images/large-previews/383/the-home-of-the-candle-1-1425911.jpg",
      index: "3"
    },
]

How can I do this in mongosh?

Is it easier to do this as a Python Array and then import back to mongodb? Thank you for your time!

Answer

Since mongoDB version 4.2+ you can do from mongosh as follow:

db.collection.update({},
[
 {
   $addFields: {
     x: {
       "$map": {
         "input": "$x",
         "as": "y",
         "in": {
           url: "$$y",
           index: {
             $indexOfArray: [
               "$x",
               "$$y"
             ]
           }
         }
       }
     }
   }
 }
],
{
  multi: true
})

Explained:

1. Replace via addFields the array x(we assume here the array field key is x) in your document with array of objects in the new format(using $indexOfArray to generate the content of the new “index” field.
2. Add {multi:true} to update all documents in the collection

Playground