Filtering an embedded array in MongoDB

Question

I have a Mongodb document that contains an an array that is deeply imbedded inside the document. In one of my action, I would like to return the entire document but filter out t

Answer 1

You can use $addToSet on the group after unwinding and matching by listed equals true.

Sample shell query:

db.collection.aggregate([
{
    $unwind: "$vehicles"
},
{
    $match: {
        "vehicles.listed": {
            $eq: true
        }
    }
},
{
    $group: {
        _id: "$id",
        vehicles: {
            "$addToSet": {
                name: "$vehicles.name",
                listed: "$vehicles.listed"
            }
        }
    }
},
{
    $project: {
        _id: 0,
        id: "$_id",
        vehicles: 1
    }
}
]).pretty();