如何解决如何在 mongoDB 中取消嵌套和分组集合
我不明白如何在 mongoDB 中展开然后嵌套集合。基本上我有两个结构如下的集合：
问题文档：
{
"_id" : 1,"questions" : [
{
"_id" : 1,"body" : "What fabric is the top made of?","date_written" : "2018-01-04","asker_name" : "yankeelover","asker_email" : "first.last@gmail.com","reported" : 0,"helpful" : 2
},{
"_id" : 2,"body" : "hey THIS IS A WEIRD QUESTION!!!!?","date_written" : "2019-04-28","asker_name" : "jbilas","reported" : 1,"helpful" : 4
},{
"_id" : 4,"body" : "How long does it last?","date_written" : "2019-07-06","asker_name" : "funnygirl","helpful" : 6
},答案文档：
{
"_id" : 1,"answers" : [
{
"_id" : 8,"body" : "DONT BUY IT! It's bad for the environment","answerer_name" : "metslover","answerer_email" : "first.last@gmail.com","helpful" : 8
},{
"_id" : 7,"body" : "Its the best! SerIoUsly magic fabric","helpful" : 7
},{
"_id" : 5,"body" : "Something pretty soft but I can't be sure","helpful" : 5,"photos" : [
{
"_id" : 1,"url" : "https://images.unsplash.com/photo-1530519729491-aea5b51d1ee1?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1651&q=80"
},答案文档中的 _id 字段与它们作为答案的问题的 _id 字段相匹配。
最终目标是让数据看起来像这样：
{
"_id": "17762","questions": [
{
"question_id": 152829,"question_body": "Why Does it look like this?","question_date": "2021-03-06T00:00:00.000Z","asker_name": "garethTheGreato","question_helpfulness": 60,"reported": false,"answers": {
"1443770": {
"id": 1443770,"body": "This question was really helpful! Thank you.","date": "2021-03-09T00:00:00.000Z","answerer_name": "SatisfiedCustomer","helpfulness": 3,"photos": []
},"1443807": {
"id": 1443807,"body": "mimk","answerer_name": "jij","photos": [
"blob:http://localhost:3000/8f6375b3-0795-4210-bef7-f112Feed8244"
]
},"1443834": {
"id": 1443834,"body": "10/10 would recomend.","answerer_name": "Krista","helpfulness": 2,"1443845": {
"id": 1443845,"body": "Thank you so much for playing my game!","date": "2021-03-10T00:00:00.000Z","answerer_name": "itsameemario","helpfulness": 1,"1443880": {
"id": 1443880,"body": "Tree","answerer_name": "Tree","helpfulness": 0,"photos": [
"blob:http://localhost:3000/123051b6-4dfb-410a-a96f-d4a5128e3056"
]
}
}
},{
"question_id": 152702,"question_body": "Please write your question here","question_date": "2021-03-05T00:00:00.000Z","asker_name": "Your nickname","question_helpfulness": 32,"answers": {}
},我遇到的问题是，当我运行查找时，我得到了一个与问题集合相关的答案数组，但我不确定如何获得他们特定问题的每组答案，因为答案是深度嵌套的.
这是我到目前为止所拥有的：（现在忽略切片和排序这些是我稍后作为项目的另一部分需要的参数）
db.prodquests.aggregate([
{ $match: { _id: 5 } },{ $unwind: '$questions' },{ $match: { 'questions.reported': { $lt: 1 } } },{ $sort: { 'questions.helpful': -1 } },{ $group: { _id: '$_id',questions: { $push: '$questions' } } },{ $project: { _id: 1,questions: { $slice: ['$questions',1] } } },{
$lookup: {
from: 'groupansphotos',localField: 'questions._id',foreignField: '_id',as: 'answers',},])
此语句的返回如下：
{
"_id" : 5,"questions" : {
"_id" : 37,"body" : "Why is this product cheaper here than other sites?","date_written" : "2018-10-18","asker_name" : "willsmith","helpful" : 4
},"answers" : [
{
"_id" : 37,"answers" : [
{
"_id" : 68,"body" : "We are selling it here without any markup from the middleman!","date_written" : "2018-08-18","answerer_name" : "Seller","answerer_email" : "null","helpful" : 4
}
]
}
]
}
本质上，我只想将答案数组分组到 _id 字段匹配的相应问题下。
先谢谢你！
解决方法
更新基于评论：
更新的查询：
db.questions.aggregate([
{ $match: { _id: 5 } },{ $unwind: '$questions' },{ $match: { 'questions.reported': { $lt: 1 } } },{ $sort: { 'questions.helpful': -1 } },{
$lookup: {
from: "answers",let: { question_id: "$questions._id" },pipeline: [
{
$match: {
$expr: { $eq: ["$_id","$$question_id"] }
}
},{ $unwind: "$answers" },{
$project: {
_id: 0,k: { $toString: "$answers._id" },v: "$$ROOT.answers"
}
}
],as: "answers"
}
},{
$group: {
_id: "$_id",questions: {
$push: {
question_id: "$questions._id",question_body: "$questions.body",question_date: "$questions.date_written",asker_name: "$questions.asker_name",question_helpfulness: "$questions.helpful",reported: "$questions.reported",answers: { $arrayToObject: "$answers" }
}
}
}
}
]);
旧查询：
注意：请修正集合名称和/或字段名称。试试这个查询：
db.questions.aggregate([
{ $match: { _id: 5 } },{
$match: {
$expr: {
$gt: [{ $size: "$answers" },0]
}
}
},answers: { $arrayToObject: "$answers" }
}
}
}
}
]);
输出：
{
"_id" : 5,"questions" : [
{
"question_id" : 2,"question_body" : "HEY THIS IS A WEIRD QUESTION!!!!?","question_date" : "2019-04-28","asker_name" : "jbilas","question_helpfulness" : 4,"reported" : 0,"answers" : {
"14" : {
"_id" : 14,"body" : "DONT BUY IT! It's bad for the environment","date_written" : "2018-01-04","answerer_name" : "metslover","answerer_email" : "first.last@gmail.com","helpful" : 8
},"15" : {
"_id" : 15,"body" : "Its the best! Seriously magic fabric","helpful" : 7
},"16" : {
"_id" : 16,"body" : "Something pretty soft but I can't be sure","helpful" : 5
}
}
},{
"question_id" : 1,"question_body" : "What fabric is the top made of?","question_date" : "2018-01-04","asker_name" : "yankeelover","question_helpfulness" : 2,"answers" : {
"11" : {
"_id" : 11,"12" : {
"_id" : 12,"13" : {
"_id" : 13,"helpful" : 5
}
}
}
]
}
测试数据：
questions 集合
{
"_id" : 5,"questions" : [
{
"_id" : 1,"body" : "What fabric is the top made of?","asker_email" : "first.last@gmail.com","helpful" : 2
},{
"_id" : 2,"body" : "HEY THIS IS A WEIRD QUESTION!!!!?","date_written" : "2019-04-28","helpful" : 4
},{
"_id" : 4,"body" : "How long does it last?","date_written" : "2019-07-06","asker_name" : "funnygirl","helpful" : 6
}
]
}
answers 集合：
/* 1 */
{
"_id" : 1,"answers" : [
{
"_id" : 11,"helpful" : 8
},{
"_id" : 12,"helpful" : 7
},{
"_id" : 13,"helpful" : 5
}
]
},/* 2 */
{
"_id" : 2,"answers" : [
{
"_id" : 14,{
"_id" : 15,{
"_id" : 16,"helpful" : 5
}
]
}
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