在聚合管道的项目阶段排除嵌套对象属性时遇到问题

Question

我有一个聚合查询，它根据文档类型返回具有不同模式的问题数组。这些文件的格式如下。有些问题可能看起来像这个

{
"_id": "ID01",
"Description": "1.Any Question?",
"answer": { "option05": "E. " },
"options": {
"option01": "A.",
"option02": "B.",
"option03": "C.",
"option04": "D.",
"option05": "E."
},
"type": "1",
"score": 10
},

并且一些问题具有以下结构

{
"_id": "ID02",
"Description": "Question Description.",
"emq": {
"emq3": {
"answer": "option12",
"explanation": "",
"question": "1 Any Qstn?"
},
"emq4": {
"answer": "option03",
"explanation": "",
"question": "2 Any Qstn?"
},
"emq5": {
"answer": "option06",
"explanation": "",
"question": "3 Any Qstn?"
}
},

"options": {
"option01": "",
"option02": "",
"option03": "",
"option04": "",
},
"type": "2",
"score": 100
},

我使用了以下聚合管道来隐藏问题中的答案，(有问题的模式已迁移，我无法更改其结构(

聚合管道

{
$lookup: {
from: 'questions',
let: {
question_id: { $toObjectId: '$qId' },
score: '$score',
},
pipeline: [
{
$match: {
$expr: {
$eq: ['$_id', '$$question_id'],
},
},
},
{
$project: {
answer: {
$cond: {
if: { $eq: ['$type', '1'] },
then: 0,
else: {
$cond: {
if: { $eq: ['$type', '3'] },
then: {
$cond: {
if: {
emq: {
regex: /^emqd+$/,
},
},
then: 0,
else: 1,
},
},
else: 1,
},
},
},
},
Description: 1,
options: 1,
type: 1,
emq: 1,
score: 1,
},
},
}

它适用于类型1的问题，但不幸的是，我无法隐藏类型2的答案，因为它们不仅在'emq'对象中，而且在字符串'emq'末尾有动态数字的嵌套'emq3'对象中，有没有办法达到下面的结果，对像这样的两个问题都隐藏答案

{
"_id": "ID01",
"Description": "1.Any Question?",
"options": {
"option01": "A.",
"option02": "B.",
"option03": "C.",
"option04": "D.",
"option05": "E."
},
"type": "1",
"score": 10
},
{
"_id": "ID02",
"Description": "Question Description.",
"emq": {
"emq3": {
"question": "1 Any Qstn?"
},
"emq4": {
"question": "2 Any Qstn?"
},
"emq5": {
"question": "3 Any Qstn?"
}
},

"options": {
"option01": "",
"option02": "",
"option03": "",
"option04": "",
},
"type": "2",
"score": 100
},

Answer 1

您可以在聚合管道中执行以下操作：

1. 使用$objectToArray将对象emq转换为k-v元组的数组
2. $project以移除字段answer和explanation
3. convert the arrayemq`返回对象

db.collection.aggregate([
{
"$addFields": {
"emq": {
"$objectToArray": "$emq"
}
}
},
{
"$project": {
"emq.v.answer": false,
"emq.v.explanation": false,
"answer": false
}
},
{
"$addFields": {
"emq": {
"$arrayToObject": "$emq"
}
}
},
{
"$addFields": {
emq: {
"$cond": {
"if": {
$eq: [
"$emq",
null
]
},
"then": "$$REMOVE",
"else": "$emq"
}
}
}
}
])

这是Mongo游乐场供您参考。