I want to aggregate data array inside another array in mongodb - mongodb

Question

I want to aggregate MongoDB documents which is having arrays inside of an array. my document was like the below.
{
"_id": "6257e31d11a9d5231c05c084",
"name": "Test Name 1",
"phone": "1234567891",
"visits": [
{
"_id": "6257e31d11a9d5231c05c069",
"date": "2-7-2021",
"samples": [
"6257f8855197613b641d494e",
....
],
"products_detailed": [
"5d725cd2c4ded7bcb480eab2",
.....
]
},
...........
]
}
and I want to get the output line below
{
"_id": "6257e31d11a9d5231c05c084",
"name": "Test Name 1",
"phone": "1234567891",
"visits": [
{
"_id": "6257e31d11a9d5231c05c069",
"date": "2-7-2021",
"samples": [
{
"_id": "6257f8855197613b641d494e",
"product_name": "Samor",
"price": 250
},
........
],
"products_detailed": [
{
"_id": "5d725cd2c4ded7bcb480eab2",
"product_name": "Pahad",
"price": 100
},
............
]
},
.........................
]
}
how can I get like this? I tried to use $lookup & group to get the output, but I am not getting the output as required me.

Answer 1

Since you have a list of visits on each document, one way to go is to $unwind and then $group at the end, like this:
db.Main.aggregate([
{
$unwind: "$visits"
},
{
"$lookup": {
"from": "Samples",
"localField": "visits.samples",
"foreignField": "_id",
"as": "samples"
}
},
{
"$lookup": {
"from": "Product Detailed",
"localField": "visits.products_detailed",
"foreignField": "_id",
"as": "products_detailed"
}
},
{
$project: {
name: 1,
phone: 1,
"visits._id": 1,
"visits.date": 1,
"visits.products_detailed": "$products_detailed",
"visits.samples": "$samples"
}
},
{
$group: {
_id: 0,
name: {$first: "$name"},
visits: {$push: "$visits"}
}
}
])
As you can see on the playground, on your data sample it will return:
[
{
"_id": 0,
"name": "Test Name 1",
"visits": [
{
"_id": "6257e31d11a9d5231c05c069",
"date": "2-7-2021",
"products_detailed": [
{
"_id": "5d725cd2c4ded7bcb480eab2",
"price": 100,
"product_name": "Pahad"
}
],
"samples": [
{
"_id": "6257f8855197613b641d494e",
"price": 250,
"product_name": "Samor"
}
]
}
]
}
]