MongoDb find opeartion on nested array having multiiple json object in it

Question

I'm having dataset in which json consists of array having multiple json in it.

The objects in the array have 4 keys, out of which 1 is missing in some of them.

I want to get the documents where all the objects in an array are missing the key.

eg, From these following documents:

{"test":1,desc:[{"price":1,"abc":"def"},{"price":2,"ac":"def"}]}
{"test":1,desc:[{"price":1,"abc":"def"},{"ac":"def"}]}
{"test":1,desc:[{"abc":"def"},{"ac":"def"}]}

I want to match only the last document.

Thanks in advance..

Answer 1

You can just use $exists :

db.collection.find(
    {
        "desc.price": {$exists: false}
    }
)

And if you want for other fields as well:

db.collection.find(
    {
        $or: [
            {
                "desc.price": {$exists: false}
            },
            {
                "desc.abc": {$exists: false}
            },
            {
                "desc.ac": {$exists: false}
            }
        ]
    }
)

One thing to note is that an empty array, ie desc = [] will always be matched by this query. if you want to ensure there's atleast one object use this query:

db.collection.find(
    {
       $and: [
           {
               "desc.price": {$exists: false}
           },
           {
               "desc.0": {$exists: true}
           }
       ]
    }
)

Answer 2

Achieved that, just made a script where i used an array to store the price thing and then used.every method for price to be undefined, it returned me the desired result which i want.