Javascript Mongoose$组（聚合）不工作

我一辈子都不知道为什么这会返回一个空数组。我有mongoose v4.1.11，运行时：

db.getCollection('stats').find({user_id:ObjectId('56410153ba86a1e8227f2781'), year: '2015-16'})

它返回5个结果

Stats.aggregate([
            { $match: {user_id:'56410153ba86a1e8227f2781', year: '2015-16'}},
                {
                    $group: {
                        _id: null,
                        started: {$sum: "$goals"}
                }
            }
        ], function (err, results) {
            console.info(results); //[] Empty array
        });

我做错了吗？文档非常清楚地表明，您可以对

\u id

使用

null

统计模型

var Stats = new Schema({
    game_id : {type: Schema.ObjectId, ref: "Games", default: null},
    user_id : {type: Schema.ObjectId, ref: "Player", default: null},
    week : Number,
    leagueID : String,
    year: String,
    app : {type: Number, default: 1},
    mins : {type: Number, default: 90},
    goals :Number,
    goal_ids : [{type: Schema.ObjectId, ref: "Goals"}],
    assists :Number,
    benchUnused :Number,
    bench :Number,
    rating :Number,
    captain :Number,
    cleanSheet :Number,
    kitWash :Number,
    ownGoal :Number,
    oppoOwnGoal :Number,
    pen :Number,
    penCondeded :Number,
    penMissed :Number,
    penSaved:Number,
    motm:Number,
    redCard:Number,
    yellowCard:Number,
    secondYellowCard:Number,
    started:Number,
    subbedOff:Number,
    subbedOn:Number,
    pts:{type: Number, default: 0},
    venue:String
})

mongoose.model('Stats', Stats);

---

你能给我们看一下

stats

文档吗？你确定

goals

是一个有效字段吗？请至少提供一个示例文档。请参阅更新，我应该说我确定一切都正确Mongoose不会在聚合管道中“自动广播”架构类型。您需要手动强制转换

ObjectId

。