使用 ObjectId 查找不正确答案

【问题标题】：lookup with ObjectId works incorrect使用 ObjectId 查找不正确
【发布时间】：2018-08-07 12:01:48
【问题描述】：

我在 mongodb 中有 2 个集合

属性集合

{
     "_id": "5b45b9612b33c41c3cdcc00c",
     "commId": "5b436da8859935243868edcc",
},
{
     "_id": "5b5844644a866c2640dcc50b",
     "commId": "5b436da8859935243868edcc",
}

社区收藏

{     
     "_id": ObjectId("5b4362e9859935243868edca"),
     "userId": "5b4329cbc5a2582294326b3b",
}
{
     "_id": ObjectId("5b436da8859935243868edcc"),
     "userId": "5b432f0ac5a2582294326b3d",
}
{
     "_id": ObjectId("5b5add46acf74732d81e9273"),
     "userId": "5b47094a28409e26d0bf0657",
}

我想通过属性中的 commId 和 cimmunities 中的 _id 加入他们

let result = await Properties.aggregate([
                        {
                            $lookup: {
                                from: 'communities',
                                localField: 'Object(commId)',   
                                foreignField: 'ObjectId(_id)',
                                as: 'author'
                            }
                        },
                        {
                            $unwind: '$author',
                        },
                        {
                            $project: {
                                commId: 1,
                                author: {
                                    'commId': '$author._id',
                                    'userId': '$author.userId'
                                }
                            }
                        },
                    ])

响应必须只有 2 个属性，但它们重复...

【问题讨论】：

标签： node.js aggregate lookup

【解决方案1】：

回应

[
    {
        "_id": "5b45b9612b33c41c3cdcc00c",
        "commId": "5b436da8859935243868edcc",
        "author": {
            "commId": "5b4362e9859935243868edca",
            "userId": "5b4329cbc5a2582294326b3b"
        }
    },
    {
        "_id": "5b45b9612b33c41c3cdcc00c",
        "commId": "5b436da8859935243868edcc",
        "author": {
            "commId": "5b436da8859935243868edcc",
            "userId": "5b432f0ac5a2582294326b3d"
        }
    },
    {
        "_id": "5b45b9612b33c41c3cdcc00c",
        "commId": "5b436da8859935243868edcc",
        "author": {
            "commId": "5b5add46acf74732d81e9273",
            "userId": "5b47094a28409e26d0bf0657"
        }
    },
    {
        "_id": "5b5844644a866c2640dcc50b",
        "commId": "5b436da8859935243868edcc",
        "author": {
            "commId": "5b4362e9859935243868edca",
            "userId": "5b4329cbc5a2582294326b3b"
        }
    },
    {
        "_id": "5b5844644a866c2640dcc50b",
        "commId": "5b436da8859935243868edcc",
        "author": {
            "commId": "5b436da8859935243868edcc",
            "userId": "5b432f0ac5a2582294326b3d"
        }
    },
    {
        "_id": "5b5844644a866c2640dcc50b",
        "commId": "5b436da8859935243868edcc",
        "author": {
            "commId": "5b5add46acf74732d81e9273",
            "userId": "5b47094a28409e26d0bf0657"
        }
    }
]

【讨论】：