Mongo Aggregation using $Max - mongodb

Question

I have a collection that stores history, i.e. a new document is created every time a change is made to the data, I need to extract fields based on the max value of a date field, however my query keeps returning either all of the dates or requires me to push the fields into an array which make the data hard to analyze for an end-user.
Expected output as CSV:
MAX(DATE), docID, url, type
1579719200216, 12371, www.foodnetwork.com, food
1579719200216, 12371, www.cnn.com, news,
1579719200216, 12371, www.wikipedia.com, info
Sample Doc:
{
"document": {
"revenueGroup": "fn",
"metaDescription": "",
"metaData": {
"audit": {
"lastModified": 1312414124,
"clientId": ""
},
"entities": [],
"docId": 1313943,
"url": ""
},
"rootUrl": "",
"taggedImages": {
"totalSize": 1,
"list": [
{
"image": {
"objectId": "woman-reaching-for-basket",
"caption": "",
"url": "",
"height": 3840,
"width": 5760,
"owner": "Facebook",
"alt": "Woman reaching for basket"
},
"tags": {
"totalSize": 4,
"list": []
}
}
]
},
"title": "The 8 Best Food Items of 2020",
"socialTitle": "The 8 Best Food Items of 2020",
"primaryImage": {
"objectId": "woman-reaching-for-basket.jpg",
"caption": "",
"url": "",
"height": 3840,
"width": 5760,
"owner": "Hero Images / Getty Images",
"alt": "Woman reaching for basket in laundry room"
},
"subheading": "Reduce your footprint with these top-performing diets",
"citations": {
"list": []
},
"docId": 1313943,
"revisionId": "1313943_1579719200216",
"templateType": "LIST",
"documentState": {
"activeDate": 579719200166,
"state": "ACTIVE"
}
},
"url": "",
"items": {
"totalSize": "",
"list": [
{
"type": "recipe",
"data": {
"comInfo": {
"list": [
{
"type": "food",
"id": "https://www.foodnetwork.com"
}
]
},
"type": ""
},
"id": 4,
"uuid": "1313ida-qdad3-42c3-b41d-223q2eq2j"
},
{
"type": "recipe",
"data": {
"comInfo": {
"list": [
{
"type": "news",
"id": "https://www.cnn.com"
},
{
"type": "info",
"id": "https://www.wikipedia.com"
}
]
},
"type": "PRODUCT"
},
"id": 11,
"uuid": "318231jc-da12-4475-8994-283u130d32"
}
]
},
"vertical": "food"
}
Below query:
db.collection.aggregate([
{
$match: {
vertical: "food",
"document.documentState.state": "ACTIVE",
"document.templateType": "LIST"
}
},
{
$unwind: "$document.items"
},
{
$unwind: "$document.items.list"
},
{
$unwind: "$document.items.list.contents"
},
{
$unwind: "$document.items.list.contents.list"
},
{
$match: {
"document.items.list.contents.list.type": "recipe",
"document.revenueGroup": "fn"
}
},
{
$sort: {
"document.revisionId": -1
}
},
{
$group: {
_id: {
_id: {
docId: "$document.docId",
date: {$max: "$document.revisionId"}
},
url: "$document.items.list.contents.list.data.comInfo.list.id",
type: "$document.items.list.contents.list.data.comInfo.list.type"
}
}
},
{
$project: {
_id: 1
}
},
{
$sort: {
"document.items.list.contents.list.id": 1, "document.revisionId": -1
}
}
], {
allowDiskUse: true
})

Answer 1

First of all, you need to go through the documentation of the $group aggregation here.
you should be doing this instead:
{
$group: {
"_id": "$document.docId"
"date": {
$max: "$document.revisionId"
},
"url": {
$first: "$document.items.list.contents.list.data.comInfo.list.id"
},
"type": {
$first:"$document.items.list.contents.list.data.comInfo.list.type"
}
}
}
This will give you the required output.