嵌套数组Sum / Count MongoDB Express

Question

全部，虽然这个问题被标记为重复，但我仍然遇到问题，通过示例搜索，我仍然无法弄清楚如何执行嵌套数组的总和/计数在mongodb，请看下面。

我使用mongoose autopopulate将数据存储在数组中，并在执行查找时显示它们。

我想查找employee.discussions数组并返回我的Discussion集合中出现的总和。我能够得到讨论的数量，但不能讨论讨论的总和。电影。

我的查询：

//Show Single Route
router.get("/:id", isLoggedin, function(req, res){


            var pipeline = [
                { "$match" : {"employeeuserid" : 'jbarmak' }},
                { "$unwind": "$discussions" },
                {
                    "$group": {
                        "_id": null,
                        "eventwaiver": { "$sum": 1 }
                    }
                }
            ];

            Employee.aggregate(pipeline)
                .exec(function(err, results){
                    if (err) throw err;
                    console.log(results);
                });


            Employee.findById(req.params.id, function (err, foundEmployee){
                if(err){
                    res.redirect('/employee');
                } else {
                    res.render('employees/show', {employee: foundEmployee});
                }
            });
});

员工收集

{
    "_id": {
        "$oid": "5ad7cf42729b4c08ae721603"
    },
    "author": {
        "id": {
            "$oid": "5ac2f25bbfb8ef001411fd01"
        },
        "username": "gmotta"
    },
    "qcerrors": [
        {
            "$oid": "5add3bc296d0a6265c04c674"
        }
    ],
    "employeesapnumber": 10001186,
    "employeeuserid": "jbarmak",
    "firstname": "jaouad",
    "lastname": "barmaki",
    "warehouseid": "1090",
    "shift": 2,
    "department": "Picking",
    "position": "Contractor",
    "hiredate": {
        "$date": "2010-12-02T00:00:00.000Z"
    },
    "myimage": "myimage-1524092737893.PNG",
    "__v": 50,
    "discussions": [
        {
            "$oid": "5add0bf211e77d08106edc9b"
        },
        {
            "$oid": "5add0c2311e77d08106edc9d"
        },
        {
            "$oid": "5add136511e77d08106edca1"
        },
        {
            "$oid": "5add148467850c0ca35ff74a"
        },
        {
            "$oid": "5add14a967850c0ca35ff74c"
        },
        {
            "$oid": "5add1eb9579cf80d86310f7d"
        },
        {
            "$oid": "5adecf7e0264cc0e7aada389"
        }
    ],
    "safetyincidents": [
        {
            "$oid": "5adeb5260264cc0e7aada385"
        }
    ]
}

如何在嵌套数组和console.log中对结果进行求和？

Dicussion系列：

{
    "_id": {
        "$oid": "5adfb054a590b10eef004b63"
    },
    "author": {
        "id": {
            "$oid": "5ac2f25bbfb8ef001411fd01"
        },
        "username": "gmotta"
    },
    "datetime": {
        "$date": "2018-02-02T14:02:00.000Z"
    },
    "reasondiscussion": "None",
    "reasontimeoff": "Bereavement",
    "warning": "None",
    "hours": 8,
    "plannedunplanned": "Unplanned",
    "occurrence": 1,
    "description": "I'm calling in because  I'm sick.",
    "shift": 1,
    "department": "Pallet-Pack",
    "employeeid": "tkane",
    "__v": 0
}