Mongodb $ lookup检索菜单和子菜单作为子文档数组

如何解决Mongodb $ lookup检索菜单和子菜单作为子文档数组

看起来像一个老问题，但是我认为该模式稍有不同，我不确定这是否是正确的模式定义，但我想这样。

import { Schema,model } from 'mongoose';
import * as mongoose from 'mongoose';
const ObjectId = mongoose.Schema.Types.ObjectId;

const MenuSchema = new Schema({
  parent: { 
    type: Schema.Types.ObjectId,ref: 'Menu',required: true,default: null },url: {
    type: String,unique: true,},title: {
    en: {
      type: String,ar: {
      type: String,type: {
    // internal or external
    type: String,required: false,default: 'internal',displayOrder: { type: Number,default: 0 },image: {
    // For icon
    type: Object,createdAt: { type: Date,default: Date.Now },createdBy: { type: ObjectId,ref: 'User' },updatedAt: { type: Date,updatedBy: { type: ObjectId,});

我的数据如下

{ 
    "_id" : ObjectId("5f97be37bf401d75ed7de8a8"),"parent" : null,"displayOrder" : NumberInt(0),"image" : null,"title" : {
        "en" : "Home","ar" : "الصفحة الرئيسية"
    },"url" : "/"
}
{ 
    "_id" : ObjectId("5f97eca04b076b2b8cb5646b"),"type" : "internal","url" : "/about","title" : {
        "en" : "About","ar" : "حول"
    },"createdAt" : ISODate("2020-10-27T09:47:12.396+0000"),"updatedAt" : ISODate("2020-10-27T09:47:12.396+0000"),"__v" : NumberInt(0),"displayOrder" : NumberInt(1),"parent" : null
}
{ 
    "_id" : ObjectId("5f99492da0c7207dfb13aa03"),"url" : "/our-partners","title" : {
        "en" : "Our Partners","ar" : "شركاؤنا"
    },"createdAt" : ISODate("2020-10-28T10:34:21.353+0000"),"updatedAt" : ISODate("2020-10-28T10:34:21.354+0000"),"displayOrder" : NumberInt(8),"parent" : null
}
{ 
    "_id" : ObjectId("5f9a7971f8443ecbdb787c4a"),"displayOrder" : NumberInt(2),"url" : "/services","title" : {
        "en" : "Services","ar" : "خدمات"
    },"createdAt" : ISODate("2020-10-29T08:12:33.366+0000"),"updatedAt" : ISODate("2020-10-29T08:12:33.366+0000"),"image" : null
}
{ 
    "_id" : ObjectId("5f9a93f3dc3f16e672d9e84e"),"displayOrder" : NumberInt(3),"url" : "products","title" : {
        "en" : "Products","ar" : "منتجات"
    },"createdAt" : ISODate("2020-10-29T10:05:39.551+0000"),"updatedAt" : ISODate("2020-10-29T10:05:39.551+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b7a9c95213c7e3736e63e"),"displayOrder" : NumberInt(4),"url" : "projects","title" : {
        "en" : "Projects","ar" : "المشاريع"
    },"createdAt" : ISODate("2020-10-30T02:29:48.863+0000"),"updatedAt" : ISODate("2020-10-30T02:29:48.863+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b7aa395213c7e3736e63f"),"displayOrder" : NumberInt(5),"url" : "gallery","title" : {
        "en" : "gallery","ar" : "صالة عرض"
    },"createdAt" : ISODate("2020-10-30T02:29:55.845+0000"),"updatedAt" : ISODate("2020-10-30T02:29:55.845+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b7af995213c7e3736e640"),"displayOrder" : NumberInt(6),"url" : "downloads","title" : {
        "en" : "Downloads","ar" : "التحميلات"
    },"createdAt" : ISODate("2020-10-30T02:31:21.205+0000"),"updatedAt" : ISODate("2020-10-30T02:31:21.205+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b7b6095213c7e3736e641"),"displayOrder" : NumberInt(7),"url" : "contact","title" : {
        "en" : "Contact","ar" : "اتصل"
    },"createdAt" : ISODate("2020-10-30T02:33:04.071+0000"),"updatedAt" : ISODate("2020-10-30T02:33:04.071+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b8459391ab38846326a43"),"parent" : "5f97eca04b076b2b8cb5646b","url" : "about","title" : {
        "en" : "Corporate Overview","ar" : "لمحة عن الشركة"
    },"createdAt" : ISODate("2020-10-30T03:11:21.048+0000"),"updatedAt" : ISODate("2020-10-30T03:11:21.048+0000"),"image" : null
}
{ 
    "_id" : ObjectId("5f9b8bb8391ab38846326a44"),"url" : "md-message","title" : {
        "en" : "Md's Message","ar" : "رسالة د"
    },"createdAt" : ISODate("2020-10-30T03:42:48.341+0000"),"updatedAt" : ISODate("2020-10-30T03:42:48.341+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b8c0e391ab38846326a45"),"url" : "certificates","title" : {
        "en" : "Certificates","ar" : "الشهادات"
    },"createdAt" : ISODate("2020-10-30T03:44:14.876+0000"),"updatedAt" : ISODate("2020-10-30T03:44:14.876+0000"),"image" : null
}
{ 
    "_id" : ObjectId("5f9b8c4e391ab38846326a46"),"parent" : "5f9a7971f8443ecbdb787c4a","url" : "before-sale-service","title" : {
        "en" : "Before Sale Service","ar" : "خدمة ما قبل البيع"
    },"createdAt" : ISODate("2020-10-30T03:45:18.489+0000"),"updatedAt" : ISODate("2020-10-30T03:45:18.489+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b8c98391ab38846326a47"),"url" : "installation","title" : {
        "en" : "Installation","ar" : "التركيب"
    },"createdAt" : ISODate("2020-10-30T03:46:32.943+0000"),"updatedAt" : ISODate("2020-10-30T03:46:32.943+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b8ccb391ab38846326a48"),"url" : "maintenance","title" : {
        "en" : "Maintenance","ar" : "اعمال صيانة"
    },"createdAt" : ISODate("2020-10-30T03:47:23.943+0000"),"updatedAt" : ISODate("2020-10-30T03:47:23.944+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b8d04391ab38846326a49"),"url" : "repairs-modernization","title" : {
        "en" : "REPAirs AND MODERNIZATION","ar" : "الإصلاح والتحديث"
    },"createdAt" : ISODate("2020-10-30T03:48:20.958+0000"),"updatedAt" : ISODate("2020-10-30T03:48:20.958+0000"),"image" : null
}
{ 
    "_id" : ObjectId("5f9b90180d34dd99a22729fc"),"parent" : "5f9b7aa395213c7e3736e63f","url" : "image-gallery","title" : {
        "en" : "Image gallery","ar" : "معرض الصور"
    },"createdAt" : ISODate("2020-10-30T04:01:28.652+0000"),"updatedAt" : ISODate("2020-10-30T04:01:28.652+0000"),"__v" : NumberInt(0)
}
{ 
    "_id" : ObjectId("5f9b903a0d34dd99a22729fd"),"url" : "video-gallery","title" : {
        "en" : "Video gallery","ar" : "معرض الفيديو"
    },"createdAt" : ISODate("2020-10-30T04:02:02.999+0000"),"updatedAt" : ISODate("2020-10-30T04:02:02.999+0000"),"__v" : NumberInt(0)
}

我的用于检索带有子项（父项：someid）的父菜单（父项：null）的查询

db.getCollection("menus").aggregate([
{
    $match: {
         'parent': null   
    }
},{
    $lookup: {
        from: 'menus',localField: '_id',foreignField: 'parent',as: 'childs'
    }
}
])

但是上述查询中我的孩子的子文档数组为空。

{ 
    "_id" : ObjectId("5f97be37bf401d75ed7de8a8"),"url" : "/","childs" : [

    ]
}
{ 
    "_id" : ObjectId("5f97eca04b076b2b8cb5646b"),"childs" : [

    ]
}
{ 
    "_id" : ObjectId("5f99492da0c7207dfb13aa03"),"childs" : [

    ]
}
{ 
    "_id" : ObjectId("5f9a7971f8443ecbdb787c4a"),"childs" : [

    ]
}
{ 
    "_id" : ObjectId("5f9a93f3dc3f16e672d9e84e"),"childs" : [

    ]
}

我想通过将父列表和子菜单作为子文档来实现如下所示的结果。目前，我的子数组在上述查询中为空。看起来很简单，但是我很难找到。请帮忙。

[
  {
    "_id": "5f97be37bf401d75ed7de8a8","parent": null,"displayOrder": 0,"image": null,"title": {
      "en": "Home","ar": "الصفحة الرئيسية"
    },"url": "/","childs": []
  },{
    "_id": "5f97eca04b076b2b8cb5646b","type": "internal","url": "/about","title": {
      "en": "About","ar": "حول"
    },"createdAt": "2020-10-27T09:47:12.396Z","updatedAt": "2020-10-27T09:47:12.396Z","__v": 0,"displayOrder": 1,"childs" : [
        { 
            "_id" : "5f9b8459391ab38846326a43","displayOrder" : 0,"title" : {
                "en" : "Corporate Overview","ar" : "لمحة عن الشركة"
            },"__v" : 0,"image" : null
        },{ 
            "_id" : "5f9b8c0e391ab38846326a45","displayOrder" : 1,"title" : {
                "en" : "Certificates","ar" : "الشهادات"
            },...  
    ]
  },]

解决方法

您在架构中的parent字段被定义为type: Schema.Types.ObjectId,，但是在数据库中，所有字段都被命名为string。那是一种矛盾。

要解决您的问题，您只需要将parent的所有string字段类型替换为ObjectId，因为$lookup使用等号匹配，而string使用ObjectId不相等。

例如，您的一个文档应该看起来像这样：

{ 
    "_id" : ObjectId("5f9b8bb8391ab38846326a44"),"parent" : ObjectId("5f97eca04b076b2b8cb5646b"),"type" : "internal","displayOrder" : NumberInt(1),"url" : "md-message","title" : {
        "en" : "Md's Message","ar" : "رسالة د"
    },"createdAt" : ISODate("2020-10-30T03:42:48.341+0000"),"updatedAt" : ISODate("2020-10-30T03:42:48.341+0000"),"__v" : NumberInt(0)
}

在本地进行了测试，可以确认其有效。