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" : "[email protected]",
"reported" : 0,
"helpful" : 2
},
{
"_id" : 2,
"body" : "HEY THIS IS A WEIRD QUESTION!!!!?",
"date_written" : "2019-04-28",
"asker_name" : "jbilas",
"asker_email" : "[email protected]",
"reported" : 1,
"helpful" : 4
},
{
"_id" : 4,
"body" : "How long does it last?",
"date_written" : "2019-07-06",
"asker_name" : "funnygirl",
"asker_email" : "[email protected]",
"reported" : 0,
"helpful" : 6
},
回答文档：
{
"_id" : 1,
"answers" : [
{
"_id" : 8,
"body" : "DONT BUY IT! It's bad for the environment",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 8
},
{
"_id" : 7,
"body" : "Its the best! Seriously magic fabric",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 7
},
{
"_id" : 5,
"body" : "Something pretty soft but I can't be sure",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"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 字段也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",
"date": "2021-03-09T00:00:00.000Z",
"answerer_name": "jij",
"helpfulness": 3,
"photos": [
"blob:http://localhost:3000/8f6375b3-0795-4210-bef7-f112feed8244"
]
},
"1443834": {
"id": 1443834,
"body": "10/10 would recomend.",
"date": "2021-03-09T00:00:00.000Z",
"answerer_name": "Krista",
"helpfulness": 2,
"photos": []
},
"1443845": {
"id": 1443845,
"body": "Thank you so much for playing my game!",
"date": "2021-03-10T00:00:00.000Z",
"answerer_name": "itsameemario",
"helpfulness": 1,
"photos": []
},
"1443880": {
"id": 1443880,
"body": "Tree",
"date": "2021-03-10T00:00:00.000Z",
"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,
"reported": false,
"answers": {}
},
我遇到的问题是，当我运行查找时，我得到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需要作为项目的另一部分的参数）
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', 0, 1] } } },
{ $unwind: '$questions' },
{
$lookup: {
from: 'groupansphotos',
localField: 'questions._id',
foreignField: '_id',
as: 'answers',
},
},
])
该语句的返回如下：
{
"_id" : 5,
"questions" : {
"_id" : 37,
"body" : "Why is this product cheaper here than other sites?",
"date_written" : "2018-10-18",
"asker_name" : "willsmith",
"asker_email" : "[email protected]",
"reported" : 0,
"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",
"reported" : 0,
"helpful" : 4
}
]
}
]
}
本质上，我只想将答案数组分组在 _id 字段匹配的相应问题下。
提前谢谢你！
根据评论更新：
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：请修复集合名称和/或字段名称。试试这个查询：
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"
}
},
{
$match: {
$expr: {
$gt: [{ $size: "$answers" }, 0]
}
}
},
{
$group: {
_id: "$_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" }
}
}
}
}
]);
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" : "[email protected]",
"reported" : 0,
"helpful" : 8
},
"15" : {
"_id" : 15,
"body" : "Its the best! Seriously magic fabric",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 7
},
"16" : {
"_id" : 16,
"body" : "Something pretty soft but I can't be sure",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"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,
"reported" : 0,
"answers" : {
"11" : {
"_id" : 11,
"body" : "DONT BUY IT! It's bad for the environment",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 8
},
"12" : {
"_id" : 12,
"body" : "Its the best! Seriously magic fabric",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 7
},
"13" : {
"_id" : 13,
"body" : "Something pretty soft but I can't be sure",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 5
}
}
}
]
}
测试数据：
questions 收藏
{
"_id" : 5,
"questions" : [
{
"_id" : 1,
"body" : "What fabric is the top made of?",
"date_written" : "2018-01-04",
"asker_name" : "yankeelover",
"asker_email" : "[email protected]",
"reported" : 0,
"helpful" : 2
},
{
"_id" : 2,
"body" : "HEY THIS IS A WEIRD QUESTION!!!!?",
"date_written" : "2019-04-28",
"asker_name" : "jbilas",
"asker_email" : "[email protected]",
"reported" : 0,
"helpful" : 4
},
{
"_id" : 4,
"body" : "How long does it last?",
"date_written" : "2019-07-06",
"asker_name" : "funnygirl",
"asker_email" : "[email protected]",
"reported" : 0,
"helpful" : 6
}
]
}
answers 集合：
/* 1 */
{
"_id" : 1,
"answers" : [
{
"_id" : 11,
"body" : "DONT BUY IT! It's bad for the environment",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 8
},
{
"_id" : 12,
"body" : "Its the best! Seriously magic fabric",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 7
},
{
"_id" : 13,
"body" : "Something pretty soft but I can't be sure",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 5
}
]
},
/* 2 */
{
"_id" : 2,
"answers" : [
{
"_id" : 14,
"body" : "DONT BUY IT! It's bad for the environment",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 8
},
{
"_id" : 15,
"body" : "Its the best! Seriously magic fabric",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 7
},
{
"_id" : 16,
"body" : "Something pretty soft but I can't be sure",
"date_written" : "2018-01-04",
"answerer_name" : "metslover",
"answerer_email" : "[email protected]",
"reported" : 0,
"helpful" : 5
}
]
}
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