聚集后的猫鼬 [英] Mongoose Populate after Aggregate

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问题描述

在运行聚合管道并填充之后，我试图获取特定的数据模型，但是我却无法做到这一点.

I am trying to get a specific data model after I run an aggregate pipeline followed by populate but I am falling just short of it.

最终所需的结果如下:

[
  {
    _accountId: "5beee0966d17bc42501f1234",
    name: "Company Name 1",
    contactEmail: "email1@email.com",
    contactName: "contact Name 1"
    reason: "Warranties",
    total: 1152,
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ]
  },
  {
    _accountId: "5beee0966d17bc42501f1235",
    name: "Company Name 2",
    contactEmail: "email2@email.com",
    contactName: "contact Name 2"
    reason: "Warranties",
    total: 1152,
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ]
  }
]

我正在从以下两个模型中收集这些数据:

I am collecting this data from the following two models:

保修 

{
  _id: "5beee0966d17bc42501f5086",
  jobsiteAddressStreet: String,
  jobsiteAddressCity: String,
  jobsiteAddressState" String,
  jobsiteAddressZip: Number,
  warrantyFee: Number,
  _accountId: {
    type: Schema.Types.ObjectId,
    ref: "accounts"
  },
  payStatus: String
}

帐户 

{
  _id: "5beee0966d17bc42501f1235",
  name: String,
  contactName: String,
  contactEmail: String
}

我当前的查询如下:

Warranty.aggregate([
    {
      $match: {
        payStatus: "Invoiced Next Billing Cycle"
      }
    },
    {
      $group: {
        _id: "$_accountId",
        total: {
          $sum: "$warrantyFee"
        },
        lineItems: {
          $push: {
            _id: "$_id",
            jobsiteAddress: {
              $concat: [
                "$jobsiteAddressStreet",
                " ",
                "$jobsiteAddressCity",
                ", ",
                "$jobsiteAddressState",
                " ",
                "$jobsiteAddressZip"
              ]
            },
            warrantyFee: "$warrantyFee"
          }
        }
      }
    },
    {
      $project: {
        reason: "Warranties",
        total: "$total",
        lineItems: "$lineItems"
      }
    }
  ])
    .then(warranties => {
      console.log(warranties);
      Account.populate(warranties, {
        path: "_id",
        select: "contactName contactEmail name"
      })
        .then(warranties => {
          res.send(warranties);
        })
        .catch(err => {
          res.status(422).send(err);
          throw err;
        });
    })
    .catch(err => {
      res.status(422).send(err);
      throw err;
    });

结果如下:

[
  {
    _id: {
      _id: "5bc39dfa331c0e2cb897b61e",
      name: "Company Name 1",
      contactEmail: "email1@email.com",
      contactName: "Contact Name 1"
    },
    reason: "Warranties",
    total: 1152,
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ]
  },
  {
    _id: {
      _id: "5bc39dfa331c0e2cb897b61e",
      name: "Company Name 2",
      contactEmail: "email2@email.com",
      contactName: "Contact Name 2"
    },
    reason: "Warranties",
    total: 1152,
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ]
  }
]

如您所见，这确实存在一些小问题.

As you can see this is really close with some minor issues.

  1. 它显示_id而不是_accountId.我默认使用此设置，因为每当我尝试在$ group中返回_accountId时，它将其标记为非累加器字段，而当我在$ project中执行此操作时，它就不会显示.数据集必须按保修"模型中的_accountId分组.
  2. 我希望将其他字段(contactName，contactEmail，name)添加到顶级对象，而不是尽可能创建子文档.这可能是简单或不可能的，因为我对填充并不十分熟悉，但却找不到直接回答我问题的任何东西.

此操作的最终目的是获取返回的对象并使用对象数组为另一个集合进行大量文档创建.

The goal at the end of this is to take the returned object and use the array of objects to do a bulk create of documents to another collection.

-回答我的特定用例-

Warranty.aggregate([
    {
      $match: {
        payStatus: "Invoiced Next Billing Cycle"
      }
    },
    {
      $group: {
        _id: "$_accountId",
        total: {
          $sum: "$warrantyFee"
        },
        lineItems: {
          $push: {
            _id: "$_id",
            jobsiteAddress: {
              $concat: [
                "$jobsiteAddressStreet",
                " ",
                "$jobsiteAddressCity",
                ", ",
                "$jobsiteAddressState",
                " ",
                "$jobsiteAddressZip"
              ]
            },
            warrantyFee: "$warrantyFee"
          }
        }
      }
    },
    {
      $lookup: {
        from: Account.collection.name,
        localField: "_id",
        foreignField: "_id",
        as: "accounts"
      }
    },
    {
      $unwind: "$accounts"
    },
    {
      $project: {
        lineItems: "$lineItems",
        reason: "Warranties",
        total: "$total",
        type: "Invoice",
        date: new Date(),
        company: "$accounts.name",
        contactName: "$accounts.contactName",
        contactEmail: "$accounts.contactEmail"
      }
    },
    {
      $addFields: {
        _accountId: "$_id"
      }
    },
    {
      $project: {
        _id: 0
      }
    }
  ])

这给了我结果:

[
  {
    lineItems: [
      {
        _id: "5be203eb3afd8098d4988152",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ],
    reason: "Warranties",
    total: 384,
    type: "Invoice",
    date: "2018-11-21T14:08:15.052Z",
    company: "Company Name 1",
    contactName: "Contact Name 1",
    contactEmail: "email1@email.com",
    _accountId: "5be203eb3afd8098d4988152",
    referenceNumber: 1542809296615
  },
  {
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ],
    reason: "Warranties",
    total: 1152,
    type: "Invoice",
    date: "2018-11-21T14:08:15.052Z",
    company: "Company Name 2",
    contactName: "Contact Name 2",
    contactEmail: "email2@email.com",
    _accountId: "5bc39dfa331c0e2cb897b61e",
    referenceNumber: 1542809295680
  }
]

推荐答案

因此，当您要求填充"聚合结果时，您实际上在这里缺少一些概念.通常，这不是您实际要做的，而是要解释要点:

So you are actually missing some concepts here when you ask to "populate" on an aggregation result. Typically this is not what you actually do, but to explain the points:

  1. aggregate()的输出不同于 Model.find()或类似的动作，因为此处的目的是重塑结果".基本上，这意味着您不再将用作聚合源的模型视为输出模型.即使您仍然在输出上保持完全相同的文档结构，甚至是这样，但是在您的情况下，输出显然仍然与源文档不同.

  1. The output of aggregate() is unlike a Model.find() or similar action since the purpose here is to "reshape the results". This basically means that the model you are using as the source of the aggregation is no longer considered that model on output. This is even true if you still maintained the exact same document structure on output, but in your case the output is clearly different to the source document anyway.

无论如何，它不再是您要从中采购的 Warranty 模型的实例，而仅仅是一个普通对象.我们可以稍后再解决.

At any rate it's no longer an instance of the Warranty model you are sourcing from, but just a plain object. We can work around that as we touch on later.

这里的重点可能是 populate()还是旧帽子" .实际上，这只是在实施的早期就添加到Mongoose的便捷功能.它真正要做的就是对单独集合中与相关的数据执行另一个查询"，然后将内存中的结果合并到原始集合输出中.

Probably the main point here is that populate() is somewhat "old hat" anyway. This is really just a convenience function added to Mongoose back in the very early days of implementation. All it really does is execute "another query" on the related data in a separate collection, and then merges the results in memory to the original collection output.

由于很多原因，这在大多数情况下并不是很有效，甚至不是理想的选择.与流行的误解相反，这实际上是不的加入".

For a lot of reasons, that's not really efficient or even desirable in most cases. And contrary to the popular misconception, this is NOT actually a "join".

对于真正的加入"，您实际上使用 $ lookup 聚合管道阶段，MongoDB使用该阶段从另一个集合返回匹配项.与 populate()不同，这实际上是在对服务器的单个请求中以单个响应完成的.这样可以避免网络开销，通常更快，并且通过真正的联接"可以执行 populate()做不到的事情.

For a real "join" you actually use the $lookup aggregation pipeline stage, which MongoDB uses to return the matching items from another collection. Unlike populate() this is actually done in a single request to the server with a single response. This avoids network overheads, is generally faster and as a "real join" allows you to do things that populate() cannot do.

改为使用$ lookup

此处非常缺少的 quick 版本是，它不是尝试在 .then()之后在 .then()中填充 populate().返回结果，您要做的是添加 $ lookup 到管道:

Use $lookup instead

The very quick version of what is missing here is that instead of attempting to populate() in the .then() after the result is returned, what you do instead is add the $lookup to the pipeline:

  { "$lookup": {
    "from": Account.collection.name,
    "localField": "_id",
    "foreignField": "_id",
    "as": "accounts"
  }},
  { "$unwind": "$accounts" },
  { "$project": {
    "_id": "$accounts",
    "total": 1,
    "lineItems": 1
  }}

请注意，此处存在一个约束，即 的输出$ lookup 是 始终 的数组.只有一个或多个相关项目要作为输出获取并不重要.管道阶段将从当前提供的文档中查找"localField" 的值，并使用该值与指定的"foreignField" 中的值进行匹配.在这种情况下，它是集合 中的 _id > $ group 定位到外部集合的 _id .

Note that there is a constraint here in that the output of $lookup is always an array. It does not matter if there is only one related item or many to be fetched as output. The pipeline stage will look for value of the "localField" from the current document presented and use that to match values in the "foreignField" specified. In this case it's the _id from the aggregation $group target to the _id of the foreign collection.

由于输出如上所述是总是数组，因此对此实例进行处理的最有效方法是简单地添加

Since the output is always an array as mentioned, the most efficient way to work with this for this instance would be to simply add an $unwind stage directly following the $lookup. All this is going to do it return a new document for each item returned in the target array, and in this case you expect it to be one. In the case where the _id is not matched in the foreign collection, the results with no matches would be removed.

请注意，这实际上是一种优化的模式，如 $ lookup + $ unwind合并.这里发生了一件特别的事情，其中​​ $ unwind 指令实际上已合并到 $ lookup 以高效的方式进行操作.您可以在那了解更多.

As a small note, this is actually an optimized pattern as described in $lookup + $unwind Coalescence within the core documentation. A special thing happens here where the $unwind instruction is actually merged into the $lookup operation in an efficient way. You can read more about that there.

从以上内容，您应该可以基本了解为什么 populate()这是错误的事情.除了输出不再由 Warranty 模型对象组成的基本事实外，该模型实际上只知道在 _accountId 属性中描述的异物，而在仍然输出.

From the above content you should be able to basically understand why populate() here is the wrong thing to do. Aside from the basic fact that the output is no longer comprised of Warranty model objects, that model really only knows about foreign items described on the _accountId property which does not exist in the output anyway.

现在，您可以实际定义一个模型，该模型可用于将输出对象显式转换为已定义的输出类型.一个简短的演示将涉及为您的应用程序添加代码，例如:

Now you can actually define a model which can be used in order to explicitly cast the output objects into a defined output type. A short demonstration of one would involve adding code to your application for this like:

// Special models

const outputSchema = new Schema({
  _id: { type: Schema.Types.ObjectId, ref: "Account" },
  total: Number,
  lineItems: [{ address: String }]
});

const Output = mongoose.model('Output', outputSchema, 'dontuseme');

然后可以使用此新的 Output 模型，以便将生成的普通JavaScript对象投射"到Mongoose文档中，以便使用

This new Output model can then be used in order to "cast" the resulting plain JavaScript objects into Mongoose Documents so that methods like Model.populate() can actually be called:

// excerpt
result2 = result2.map(r => new Output(r));   // Cast to Output Mongoose Documents

// Call populate on the list of documents
result2 = await Output.populate(result2, { path: '_id' })
log(result2);

由于 Output 具有定义的架构，该架构知道 Model.populate()文档的 _id 字段上的引用">知道需要做什么并退回项目.

Since Output has a schema defined that is aware of the "reference" on the _id field of it's documents the Model.populate() is aware of what it needs to do and returns the items.

请注意，因为这实际上会生成另一个查询.即:

Beware though since this actually generates another query. i.e:

Mongoose: warranties.aggregate([ { '$match': { payStatus: 'Invoiced Next Billing Cycle' } }, { '$group': { _id: '$_accountId', total: { '$sum': '$warrantyFee' }, lineItems: { '$push': { _id: '$_id', address: { '$trim': { input: { '$reduce': { input: { '$objectToArray': '$address' }, initialValue: '', in: { '$concat': [ '$$value', ' ', [Object] ] } } }, chars: ' ' } } } } } } ], {})
Mongoose: accounts.find({ _id: { '$in': [ ObjectId("5bf4b591a06509544b8cf75c"), ObjectId("5bf4b591a06509544b8cf75b") ] } }, { projection: {} })

第一行是聚合输出，然后您再次与服务器联系以返回相关的 Account 模型条目.

Where the first line is the aggregate output, and then you are contacting the server again in order to return the related Account model entries.

这些是您的选择，但是应该很清楚，现代的方法是使用，这实际上不是 populate()的含义做.

So those are your options, but it should be pretty clear that the modern approach to this is instead to use $lookup and get a real "join" which is not what populate() is actually doing.

其中列出了所有这些方法在实践中实际工作方式的完整说明.这里采取了一些 artistic许可，因此所表示的模型可能与您拥有的不完全相同，但是有足够的方式来再现基本概念:

Included is a listing as a full demonstration of how each of these approaches actually work in practice. Some artistic licence is taken here, so the models represented may not be exactly the same as what you have, but there is enough there to demonstrate the basic concepts in a reproducible way:

const { Schema } = mongoose = require('mongoose');

const uri = 'mongodb://localhost:27017/joindemo';
const opts = { useNewUrlParser: true };

// Sensible defaults
mongoose.Promise = global.Promise;
mongoose.set('debug', true);
mongoose.set('useFindAndModify', false);
mongoose.set('useCreateIndex', true);

// Schema defs

const warrantySchema = new Schema({
  address: {
    street: String,
    city: String,
    state: String,
    zip: Number
  },
  warrantyFee: Number,
  _accountId: { type: Schema.Types.ObjectId, ref: "Account" },
  payStatus: String
});

const accountSchema = new Schema({
  name: String,
  contactName: String,
  contactEmail: String
});

// Special models


const outputSchema = new Schema({
  _id: { type: Schema.Types.ObjectId, ref: "Account" },
  total: Number,
  lineItems: [{ address: String }]
});

const Output = mongoose.model('Output', outputSchema, 'dontuseme');

const Warranty = mongoose.model('Warranty', warrantySchema);
const Account = mongoose.model('Account', accountSchema);


// log helper
const log = data => console.log(JSON.stringify(data, undefined, 2));

// main
(async function() {

  try {

    const conn = await mongoose.connect(uri, opts);

    // clean models
    await Promise.all(
      Object.entries(conn.models).map(([k,m]) => m.deleteMany())
    )

    // set up data
    let [first, second, third] = await Account.insertMany(
      [
        ['First Account', 'First Person', 'first@example.com'],
        ['Second Account', 'Second Person', 'second@example.com'],
        ['Third Account', 'Third Person', 'third@example.com']
      ].map(([name, contactName, contactEmail]) =>
        ({ name, contactName, contactEmail })
      )
    );

    await Warranty.insertMany(
      [
        {
          address: {
            street: '1 Some street',
            city: 'Somewhere',
            state: 'TX',
            zip: 1234
          },
          warrantyFee: 100,
          _accountId: first,
          payStatus: 'Invoiced Next Billing Cycle'
        },
        {
          address: {
            street: '2 Other street',
            city: 'Elsewhere',
            state: 'CA',
            zip: 5678
          },
          warrantyFee: 100,
          _accountId: first,
          payStatus: 'Invoiced Next Billing Cycle'
        },
        {
          address: {
            street: '3 Other street',
            city: 'Elsewhere',
            state: 'NY',
            zip: 1928
          },
          warrantyFee: 100,
          _accountId: first,
          payStatus: 'Invoiced Already'
        },
        {
          address: {
            street: '21 Jump street',
            city: 'Anywhere',
            state: 'NY',
            zip: 5432
          },
          warrantyFee: 100,
          _accountId: second,
          payStatus: 'Invoiced Next Billing Cycle'
        }
      ]
    );

    // Aggregate $lookup
    let result1 = await Warranty.aggregate([
      { "$match": {
        "payStatus": "Invoiced Next Billing Cycle"
      }},
      { "$group": {
        "_id": "$_accountId",
        "total": { "$sum": "$warrantyFee" },
        "lineItems": {
          "$push": {
            "_id": "$_id",
            "address": {
              "$trim": {
                "input": {
                  "$reduce": {
                    "input": { "$objectToArray": "$address" },
                    "initialValue": "",
                    "in": {
                      "$concat": [ "$$value", " ", { "$toString": "$$this.v" } ] }
                  }
                },
                "chars": " "
              }
            }
          }
        }
      }},
      { "$lookup": {
        "from": Account.collection.name,
        "localField": "_id",
        "foreignField": "_id",
        "as": "accounts"
      }},
      { "$unwind": "$accounts" },
      { "$project": {
        "_id": "$accounts",
        "total": 1,
        "lineItems": 1
      }}
    ])

    log(result1);

    // Convert and populate
    let result2 = await Warranty.aggregate([
      { "$match": {
        "payStatus": "Invoiced Next Billing Cycle"
      }},
      { "$group": {
        "_id": "$_accountId",
        "total": { "$sum": "$warrantyFee" },
        "lineItems": {
          "$push": {
            "_id": "$_id",
            "address": {
              "$trim": {
                "input": {
                  "$reduce": {
                    "input": { "$objectToArray": "$address" },
                    "initialValue": "",
                    "in": {
                      "$concat": [ "$$value", " ", { "$toString": "$$this.v" } ] }
                  }
                },
                "chars": " "
              }
            }
          }
        }
      }}
    ]);

    result2 = result2.map(r => new Output(r));

    result2 = await Output.populate(result2, { path: '_id' })
    log(result2);

  } catch(e) {
    console.error(e)
  } finally {
    process.exit()
  }

})()

完整的输出:

Mongoose: dontuseme.deleteMany({}, {})
Mongoose: warranties.deleteMany({}, {})
Mongoose: accounts.deleteMany({}, {})
Mongoose: accounts.insertMany([ { _id: 5bf4b591a06509544b8cf75b, name: 'First Account', contactName: 'First Person', contactEmail: 'first@example.com', __v: 0 }, { _id: 5bf4b591a06509544b8cf75c, name: 'Second Account', contactName: 'Second Person', contactEmail: 'second@example.com', __v: 0 }, { _id: 5bf4b591a06509544b8cf75d, name: 'Third Account', contactName: 'Third Person', contactEmail: 'third@example.com', __v: 0 } ], {})
Mongoose: warranties.insertMany([ { _id: 5bf4b591a06509544b8cf75e, address: { street: '1 Some street', city: 'Somewhere', state: 'TX', zip: 1234 }, warrantyFee: 100, _accountId: 5bf4b591a06509544b8cf75b, payStatus: 'Invoiced Next Billing Cycle', __v: 0 }, { _id: 5bf4b591a06509544b8cf75f, address: { street: '2 Other street', city: 'Elsewhere', state: 'CA', zip: 5678 }, warrantyFee: 100, _accountId: 5bf4b591a06509544b8cf75b, payStatus: 'Invoiced Next Billing Cycle', __v: 0 }, { _id: 5bf4b591a06509544b8cf760, address: { street: '3 Other street', city: 'Elsewhere', state: 'NY', zip: 1928 }, warrantyFee: 100, _accountId: 5bf4b591a06509544b8cf75b, payStatus: 'Invoiced Already', __v: 0 }, { _id: 5bf4b591a06509544b8cf761, address: { street: '21 Jump street', city: 'Anywhere', state: 'NY', zip: 5432 }, warrantyFee: 100, _accountId: 5bf4b591a06509544b8cf75c, payStatus: 'Invoiced Next Billing Cycle', __v: 0 } ], {})
Mongoose: warranties.aggregate([ { '$match': { payStatus: 'Invoiced Next Billing Cycle' } }, { '$group': { _id: '$_accountId', total: { '$sum': '$warrantyFee' }, lineItems: { '$push': { _id: '$_id', address: { '$trim': { input: { '$reduce': { input: { '$objectToArray': '$address' }, initialValue: '', in: { '$concat': [ '$$value', ' ', [Object] ] } } }, chars: ' ' } } } } } }, { '$lookup': { from: 'accounts', localField: '_id', foreignField: '_id', as: 'accounts' } }, { '$unwind': '$accounts' }, { '$project': { _id: '$accounts', total: 1, lineItems: 1 } } ], {})
[
  {
    "total": 100,
    "lineItems": [
      {
        "_id": "5bf4b591a06509544b8cf761",
        "address": "21 Jump street Anywhere NY 5432"
      }
    ],
    "_id": {
      "_id": "5bf4b591a06509544b8cf75c",
      "name": "Second Account",
      "contactName": "Second Person",
      "contactEmail": "second@example.com",
      "__v": 0
    }
  },
  {
    "total": 200,
    "lineItems": [
      {
        "_id": "5bf4b591a06509544b8cf75e",
        "address": "1 Some street Somewhere TX 1234"
      },
      {
        "_id": "5bf4b591a06509544b8cf75f",
        "address": "2 Other street Elsewhere CA 5678"
      }
    ],
    "_id": {
      "_id": "5bf4b591a06509544b8cf75b",
      "name": "First Account",
      "contactName": "First Person",
      "contactEmail": "first@example.com",
      "__v": 0
    }
  }
]
Mongoose: warranties.aggregate([ { '$match': { payStatus: 'Invoiced Next Billing Cycle' } }, { '$group': { _id: '$_accountId', total: { '$sum': '$warrantyFee' }, lineItems: { '$push': { _id: '$_id', address: { '$trim': { input: { '$reduce': { input: { '$objectToArray': '$address' }, initialValue: '', in: { '$concat': [ '$$value', ' ', [Object] ] } } }, chars: ' ' } } } } } } ], {})
Mongoose: accounts.find({ _id: { '$in': [ ObjectId("5bf4b591a06509544b8cf75c"), ObjectId("5bf4b591a06509544b8cf75b") ] } }, { projection: {} })
[
  {
    "_id": {
      "_id": "5bf4b591a06509544b8cf75c",
      "name": "Second Account",
      "contactName": "Second Person",
      "contactEmail": "second@example.com",
      "__v": 0
    },
    "total": 100,
    "lineItems": [
      {
        "_id": "5bf4b591a06509544b8cf761",
        "address": "21 Jump street Anywhere NY 5432"
      }
    ]
  },
  {
    "_id": {
      "_id": "5bf4b591a06509544b8cf75b",
      "name": "First Account",
      "contactName": "First Person",
      "contactEmail": "first@example.com",
      "__v": 0
    },
    "total": 200,
    "lineItems": [
      {
        "_id": "5bf4b591a06509544b8cf75e",
        "address": "1 Some street Somewhere TX 1234"
      },
      {
        "_id": "5bf4b591a06509544b8cf75f",
        "address": "2 Other street Elsewhere CA 5678"
      }
    ]
  }
]

这篇关于聚集后的猫鼬的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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