MongoDb $lookup-Abfrage mit mehreren Feldern aus dem Objektarray

Versuchen Sie es mit diesem

 db.getCollection('Event').aggregate([{ "$unwind": "$attendees" },
        { "$lookup" : { "from" : "Contact", "localField" : "attendees.contact", "foreignField": "_id", "as" : "contactlist" } },
        { "$unwind": "$contactlist" },
         { "$project" :{
                    "attendees.type" : 1,
                    "attendees.status" : 1,
                    "attendees.contact" : "$contactlist",
                      "name": 1, "_id": 1
                       }
        },
        {
            "$group" : {
                _id : "$_id" ,
                "name" : { $first : "$name" }, 
                "attendees" : { $push : "$attendees" }
            }
        }
        ])