mongodb is it possible to get all keys and values of object in documents in the collection?

Question

Is it possible to get all keys and values of object in documents in the collection?

I have a collection in mongo db with structure like

[{
    _id: '55534c2e2750b4394debedd2',
    selected_options: {
        name: 'test',
        size: 'S',
        color: 'red'
    }
},
 {
    _id: '55534c2e2750b4394debedd3',
    selected_options: {
        name: 'test2',
        size: 'S',
        color: 'red'
    }

},
{
    _id: '55534e087f01fa2a4d30f7f5',
    selected_options: {
        name: 'test3',
        size: 'm',
        color: 'green'
    }
}
........
]

how can i get output like :

[{
    name: 'name',
    values: ['test', 'test2', 'test3']
},
{
    name: 'size',
    values: ['S', 'm']
},
{
    name: 'color',
    values: ['red', 'green']
}
]

Answer 1

I think you have no option to achieve your result without processing on your client side. However you can try Aggregation Framework to achieve something similar to your desired output with just a single query.

db.yourCollection.aggregate([
                               {$group: 
                                  {
                                     _id: null,
                                     names: {$addToSet: '$selected_options.name'},
                                     sizes: {$addToSet: '$selected_options.size'},
                                     colors: {$addToSet: '$selected_options.color'},
                                  }
                               },
                               {$project:
                                  {_id: 0, names: 1, colors: 1, sizes: 1}
                               }
                           ])

This will output the following:

{
   names: ['test', 'test2', 'test3'],
   sizes: ['S', 'm'],
   colors: ['red', 'green']
}