MongoDB：如何使用查找查询填充嵌套对象？

如何解决MongoDB：如何使用查找查询填充嵌套对象？

我正在获取对其他集合具有一些嵌套引用的记录列表，我想使用 mongoDb 聚合查找查询填充对象数组内的嵌套 ObjectId。

DB 集合结构是这样的：

{
  subject: {type: String},body: {type: String},recipients: [{
    userId: {type: mongoose.Schema.Types.ObjectId,ref: 'User'},stutus: {type: String,enum: ['pending','accepted','rejected'],default:'pending'}
  }],sender: {type: mongoose.Schema.Types.ObjectId,ref: 'User'}
}

我的期望：

[{
  subject: 'Some subject here.',body: 'Lorem ipsum dolor emit set',recipients: [{
    userId: {firstName: 'John',lastName: 'Doe'},status: 'accepted'
  },{
    userId: {firstName: 'Jane',status: 'accepted'
  }],sender: {firstName: 'Jacobs','lastName': 'Doe'}
},{
  subject: 'Some subject here.',recipients: [{
    userId: {firstName: 'Jane',status: 'rejected'
  },{
    userId: {firstName: 'John','lastName': 'Doe'}
}]

任何帮助将不胜感激。

解决方法

• $unwind 解构 recipients 数组
• $lookup 包含 recipients.userId 的用户集合
• $unwind 解构 recipients.userId 数组
• $lookup 包含 sender 的用户集合
• $unwind 解构 sender 数组
• $group by _id 并重建 recipients 数组

db.mails.aggregate([
  { $unwind: "$recipients" },{
    $lookup: {
      from: "users",localField: "recipients.userId",foreignField: "_id",as: "recipients.userId"
    }
  },{ $unwind: "$recipients.userId" },localField: "sender",as: "sender"
    }
  },{ $unwind: "$sender" },{
    $group: {
      _id: "$_id",recipients: { $push: "$recipients" },subject: { $first: "$subject" },body: { $first: "$body" },sender: { $first: "$sender" }
    }
  }
])

Playground

,

试试这个：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools" package="com.arge24.assistant24_mobile">
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  <uses-permission android:name="android.permission.BIND_ACCESSIBILITY_SERVICE" tools:ignore="ProtectedPermissions" />

  <application android:name="io.flutter.app.FlutterApplication" android:label="Assistant 24" android:allowBackup="false" android:icon="@mipmap/ic_launcher" android:roundIcon="@mipmap/ic_launcher_round" android:usesCleartextTraffic="true">
    <activity android:name=".MainActivity" android:launchMode="singleTop" android:theme="@style/LaunchTheme" android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode" android:hardwareAccelerated="true" android:windowSoftInputMode="adjustResize" android:showWhenLocked="true" android:turnScreenOn="true">
   
      <meta-data android:name="io.flutter.embedding.android.NormalTheme" android:resource="@style/NormalTheme" />

      <meta-data android:name="io.flutter.embedding.android.SplashScreenDrawable" android:resource="@drawable/launch_background" />
      <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
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    </activity>
    <receiver android:name="BootCompleteReceiver" android:enabled="true" android:exported="true">
      <intent-filter android:priority="1000">
        <action android:name="android.intent.action.BOOT_COMPLETED" />
        <action android:name="android.intent.action.QUICKBOOT_POWERON" />
        <action android:name="android.intent.action.LOCKED_BOOT_COMPLETED" />
        <action android:name="android.intent.action.REBOOT" />
      </intent-filter>
    </receiver>
 
  </application>
</manifest>