$ lookup用于聚合两层关系 [英] $lookup for aggregation for two layer relationship
本文介绍了$ lookup用于聚合两层关系的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
让我以此开头作为开头，说我可能没有通过非规范化来正确设计用户和公司关系，但是我该如何使用已有的东西呢?
Let me preface this by saying I may have not designed the User and corporation relationship correctly by not denormalizing, but how can I do it with what I have?
假设我的收藏集中有以下文档Classes Collecton
Lets say I have the following document in my collection Classes Collecton
{
"_id": ObjectId("5df58d45244a850d54b922c8"),
"mentors" : {
"numOfMentors" : NumberInt(1),
"mentorList" : [
ObjectId("5c9ba636347bb645e0865283")
]
},
"lessons": [
{
"_id": ObjectId("5db221be211d7b68ac8be618"),
"mentorData": {
"objective": "Ensuring students that making mistakes is normal and that it is a part of life",
"task": "Post a video explaining obstacles that you had to overcome as a programmer",
"dueDate": "2019-12-14T15:26:10.000+0000"
},
"studentData": {
"objective": "Learning that failures help you grow",
"task": "Post a video explaining obstacles that you have overcame",
"dueDate": "2020-01-14T22:26:10.000+0000" <---- CHECKING THIS DATE
},
"title": "How to overcome obstacles",
"comments": []
}
]
}
并且我有mentors.mentorList
{
"_id" : ObjectId("5c9ba636347bb645e0865283"),
"securityQuestions" : {
"isSetup" : false
},
"videos" : [
],
"events" : [
],
"name" : "Jackie Uphill",
"email" : "laura@stemuli.net",
"password" : "$2y$10$cmCZ.bnS/qK25wqp9i4bB.RMmctxd02Rlmc/cGN5XmUh46GMYigWu",
"account_type" : "volunteer",
"district" : "Dallas",
"date" : ISODate("2019-03-27T16:35:02.968+0000"),
"__v" : NumberInt(0),
"chat" : ObjectId("5c9ba637347bb645e0865284"),
"corporation" : ObjectId("5d83749fb57cc711487f1cc2"),
"profile" : ObjectId("5c9ba637347bb645e0865286"),
"profile_type" : "VolunteerProfile",
}
有法人:
{
"_id" : ObjectId("5d83749fb57cc711487f1cc2"),
"name" : "STEMuli Education"
}
我正在汇总如下:
Class.aggregate([
{ $match: { "students.studentList": req.user._id } },
{ $unwind: "$lessons" },
{
$addFields: {
date: {
$dateToString: {
format: "%Y-%m-%d",
date: "$lessons.studentData.dueDate"
}
}
}
},
{
$match: {
$and: [
{ date: { $gte: startDate } },
{ date: { $lte: endDate } }
]
}
},
{ $group: { _id: "$_id", lessons: { $push: "$lessons" } } }
])
哪个返回此...
{
"lessonImage": {
"url": "https://stemsandbox.blob.core.windows.net/stemuli/lesson-picture-a406bd19-0677-4b60-909e-7de2ca3c6f93.jpg",
"originalname": "nintendo-switch-console.jpg",
"mimetype": "image/jpeg",
"blobName": "lesson-picture-a406bd19-0677-4b60-909e-7de2ca3c6f93.jpg",
"container": "stemuli",
"blob": "lesson-picture-a406bd19-0677-4b60-909e-7de2ca3c6f93.jpg",
"size": "147469",
"etag": "\"0x8D797B8F1EC9C39\"",
"createdOn": "2020-01-12T23:41:28.588Z"
},
"_id": "5db221be211d7b68ac8be619",
"mentorData": {
"objective": "Learn to make a single web page web app",
"task": "Create a short video instructing how to setup environment",
"dueDate": "2019-02-02T22:26:10.000Z"
},
"studentData": {
"objective": "Program a single page web app in React",
"task": "Program a single page web app in React and submit by october 30th",
"dueDate": "2020-01-22T22:26:10.000Z"
},
"title": "Learning to program in React",
}
我希望这样，我想向导师和公司填充
注意 mentors字段
I want it to be like this I want to populate the mentor AND the corporation
Note mentors field
{
"lessonImage": {
"url": "https://stemsandbox.blob.core.windows.net/stemuli/lesson-picture-a406bd19-0677-4b60-909e-7de2ca3c6f93.jpg",
"originalname": "nintendo-switch-console.jpg",
"mimetype": "image/jpeg",
"blobName": "lesson-picture-a406bd19-0677-4b60-909e-7de2ca3c6f93.jpg",
"container": "stemuli",
"blob": "lesson-picture-a406bd19-0677-4b60-909e-7de2ca3c6f93.jpg",
"size": "147469",
"etag": "\"0x8D797B8F1EC9C39\"",
"createdOn": "2020-01-12T23:41:28.588Z"
},
"_id": "5db221be211d7b68ac8be619",
"mentorData": {
"objective": "Learn to make a single web page web app",
"task": "Create a short video instructing how to setup environment",
"dueDate": "2019-02-02T22:26:10.000Z"
},
"studentData": {
"objective": "Program a single page web app in React",
"task": "Program a single page web app in React and submit by october 30th",
"dueDate": "2020-01-22T22:26:10.000Z"
},
"title": "Learning to program in React",
"classId": "5e1baea87fcee8639cbce29d",\
//FIELD BELOW ADDED
"mentors": [
{
"name" : "Jackie Uphill",
"corporation": {"name": "Jedi Academy"}
}
]
}
推荐答案
You can run below $lookup with custom pipeline to bring the data from other collections:
{
$lookup: {
from: "users",
let: { mentor_ids: "$mentors" },
pipeline: [
{ $match: { $expr: { $in: ["$_id", "$$mentor_ids" ] } } },
{
$lookup: {
from: "corporation",
localField: "corporation",
foreignField: "_id",
as: "corporation"
}
},
{ $unwind: "$corporation" },
{
$project: {
name: 1,
"corporation.name": 1
}
}
],
as: "mentors"
}
}
这篇关于$ lookup用于聚合两层关系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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