How to use field value as key name in Mongodb result

Question

Can somebody tell me please if is possible to use field value as key in mongodb result. If I have documentes like

{'code': 'xxx', 'item': 'yyy'}
{'code': 'ooo', 'item': 'eee'}

I would like to get result where code value will be the key like

{'xxx': 'yyy'}, {'ooo': 'eee'}

Answer 1

You have to use $arrayToObject if you want to build your keys dynamically. It takes an array of k and v fields as a parameter. To make it root you can use $replaceRoot stage, try:

db.col.aggregate([
    {
        $replaceRoot: {
            newRoot: { $arrayToObject: [ [ { k: "$code", v: "$item" } ] ]}
        }
    }
])

Answer 2

I don't think thats possible. Mongo leaves the interpretation of the result to the application. Thats why mongodb is a shema-less database.