我创建了一个聚合管道，它执行以下操作:

1. 转到自定义集合并按 _id 查找
2. 转到默认集合并按 id 查找，将其附加为默认值
3. 转到 Style collection 并通过 id 查找，将其附加为 Style

代码:

Custom.aggregate([{
        $match: {
            '_id': mongoose.Types.ObjectId(req.params.id)
        }
    },
    {
        $lookup: {
            from: 'styles',
            localField: 'styleId',
            foreignField: 'id',
            as: 'style'
        }
    },
    {
        $unwind: '$style'
    },
    {
        $lookup: {
            from: 'default',
            localField: 'styleId',
            foreignField: 'id',
            as: 'default'
        }
    },
    {
        $unwind: '$default'
    },
]).then(docs => res.json(docs))
}

这是当前输出:

{
    "_id": "597774cc09064e2e4e9fedb7",
    "updatedAt": "2017-07-25T16:41:48.823Z",
    "createdAt": "2017-07-25T16:41:48.823Z",
    "styleId": "401648805",
    "colorId": null,
    "selectedOption": null,
    "deselectedOption": null,
    "currentOptions": [],
    "requiredItems": [],
    "includedItems": [],
    "furtherRemovals": [],
    "furtherAdditions": [],
    "excludedItems": [],
    "name": [],
    "__v": 0,
    "style": {
        "_id": "5902276effabb8bd2926be71",
        "id": "401648805",
        "name": "Luxury 4dr Sedan (2.0L 4cyl Turbo 8A)",
        "createdAt": "2017-07-26T15:28:36.778Z",
        "updatedAt": "2017-07-26T15:49:14.366Z"
    },
    "default": {
        "_id": "5978bfef32d246877e9cb363",
        "updatedAt": "2017-07-26T16:14:39.779Z",
        "createdAt": "2017-07-26T16:14:39.779Z",
        "id": "401648805",
        "requiredItems": [],
        "includedItems": [],
        "furtherRemovals": [],
        "furtherAdditions": [],
        "excludedItems": [],
        "__v": 0
    }
}

我试图将我的自定义对象包装在一个“自定义”命名对象中，它更适合我们的数据结构:

{
    "custom": {
        "_id": "597774cc09064e2e4e9fedb7",
        "updatedAt": "2017-07-25T16:41:48.823Z",
        "createdAt": "2017-07-25T16:41:48.823Z",
        "styleId": "401648805",
        "colorId": null,
        "selectedOption": null,
        "deselectedOption": null,
        "currentOptions": [],
        "requiredItems": [],
        "includedItems": [],
        "furtherRemovals": [],
        "furtherAdditions": [],
        "excludedItems": [],
        "name": [],
        "__v": 0,
    },
    "style": {
        "_id": "5902276effabb8bd2926be71",
        "id": "401648805",
        "name": "Luxury 4dr Sedan (2.0L 4cyl Turbo 8A)",
        "createdAt": "2017-07-26T15:28:36.778Z",
        "updatedAt": "2017-07-26T15:49:14.366Z"
    },
    "default": {
        "_id": "5978bfef32d246877e9cb363",
        "updatedAt": "2017-07-26T16:14:39.779Z",
        "createdAt": "2017-07-26T16:14:39.779Z",
        "id": "401648805",
        "requiredItems": [],
        "includedItems": [],
        "furtherRemovals": [],
        "furtherAdditions": [],
        "excludedItems": [],
        "__v": 0
    }
}

我认为它与聚合管道中的 $group 有关，但我不确定如何构建它。任何帮助将不胜感激 - MonogoDB/Mongoose 相对较新。

最佳答案

就我个人而言，我会 $project在 $match 之后将 $$ROOT 更改为管道的新名称“就在开头” :

Custom.aggregate([
     { $match: {
       '_id': mongoose.Types.ObjectId(req.params.id)
     }},
     { $project: { _id: 0, custom: '$$ROOT' } },
     { $lookup: {
       from: 'styles',
       localField: 'custom.styleId',
       foreignField: 'id',
       as: 'style'
     }},
     { $unwind: '$style' },
     { $lookup: {
       from: 'default',
       localField: 'custom.styleId',
       foreignField: 'id',
       as: 'default'
     }},
     { $unwind: '$default' }
]).then(docs => res.json(docs))

它是最少的代码并且兼容自$lookup以来的所有版本被介绍。

关于node.js - 将整个原始文档置于新的属性名称下，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/45333504/