node.js - 从 mongodb 数组中提取元素

Question

我有一个问题，我在这个问题上浪费了比应有的时间更多的时间，而且我似乎不明白我做错了什么。

我在 MongoDB 中有以下文档:

{
    "personal": {
        ...
    },
    "preferences": {
        ....
    },
    "_id": "5b2efdad564191054807c2b1",
    "pets": [],
    "conversations": [
        {
            "unread": 1,
            "participants": [
                {
                    "_id": "5b2efdcd564191054807c2b2",
                    "name": "Mighty Jules"
                }
            ],
            "messages": [
                {
                    "sender": "self",
                    "timestamp": "2018-06-24T12:29:50.656Z",
                    "_id": "5b2f8ebede342a12a8dcc9d2",
                    "text": "..."
                },
                {
                    "sender": "self",
                    "timestamp": "2018-06-24T12:29:58.022Z",
                    "_id": "5b2f8ec6de342a12a8dcc9d8",
                    "text": "..."
                },
                {
                    "sender": "5b2efdcd564191054807c2b2",
                    "timestamp": "2018-06-24T12:30:27.562Z",
                    "_id": "5b2f8ee3de342a12a8dcc9e5",
                    "text": "..."
                },
                {
                    "sender": "self",
                    "timestamp": "2018-06-24T12:32:48.034Z",
                    "_id": "5b2f8f70d3a83e25bc1abbb2",
                    "text": "..."
                },
                {
                    "sender": "self",
                    "timestamp": "2018-06-24T12:36:20.027Z",
                    "_id": "5b2f9044d4137828283c5a60",
                    "text": "..."
                },
                {
                    "sender": "5b2efdcd564191054807c2b2",
                    "timestamp": "2018-06-24T12:37:39.965Z",
                    "_id": "5b2f90939b4b2a4af8cf50db",
                    "text": "..."
                }
            ],
            "last_message": "2018-06-24T12:37:39.965Z",
            "_id": "5b2efdcd564191054807c2b2"
        },
        {
            "unread": 1,
            "participants": [
                {
                    "_id": "5b300ff657957c1aa0ed0576",
                    "name": "Super Frank"
                }
            ],
            "messages": [
                {
                    "sender": "5b300ff657957c1aa0ed0576",
                    "timestamp": "2018-06-24T21:42:49.392Z",
                    "_id": "5b30105957957c1aa0ed0583",
                    "text": "..."
                }
            ],
            "last_message": "2018-06-24T21:42:49.392Z",
            "_id": "5b300ff657957c1aa0ed0576"
        }
    ],
    "created_date": "2018-06-24T02:10:53.314Z",
    "lastLogin_date": "2018-06-24T02:10:53.314Z",
    "lastUpdate_date": "2018-06-25T02:09:53.281Z",
    "__v": 0
}

我正在尝试使用 Mongoose 删除几条消息:

const user = await User.findOneAndUpdate(
    {
        _id: mongoose.Types.ObjectId("5b2efdad564191054807c2b1"), //Which is the one that doc
        "conversations._id": mongoose.Types.ObjectId("5b2efdcd564191054807c2b2")
    },
    {
        $pull: {
            "conversations.$.messages": {
                $in: [
                    { _id: mongoose.Types.ObjectId("5b2f9044d4137828283c5a60") },
                    { _id: mongoose.Types.ObjectId("5b2f90939b4b2a4af8cf50db") }
                ]
            }
        }
    },
    {
        new: true,
        projection: {
            conversations: 1
        }
    }
);

在响应中我得到了相同的结果，没有删除任何内容，也没有收到任何错误。

Answer 1

首先，示例文档中的_id是字符串，而不是ObjectId。其次，$pull 语法是错误的。请阅读https://docs.mongodb.com/manual/reference/operator/update/pull/#remove-items-from-an-array-of-documents 。应该是:

{
    $pull: {
        "conversations.$.messages": { 
            "_id": {
                "$in": ["5b2f9044d4137828283c5a60", "5b2f90939b4b2a4af8cf50db"]
            } 
        }
    }
}

如果您想要的话，它将从第一个匹配对话中提取消息。如果您想从所有匹配对话中删除消息，则需要使用$[]相反:“conversations.$[].messages”