How to have multiple nested arrays in an array - mongodb

Question

I have the collection data from a csv file with header. When i run my query
db.ties.aggregate(
[
{
$group:
{
_id: { "SHOP": "$SHOP" },
isLinkedTo: { $push: { "PERSON": "$PERSON", "CITY": "$CITY", "ROOM": "$ROOM", "STYLE": "$STYLE", "hasDonated": {"DATE": "$DATE", "OBJECT": "$OBJECT", "COST": "$COST", "COLOR": "$COLOR", "PAYMENT": "$PAYMENT"}}}
}
},
{ $out: "ties"}
],
{ allowDiskUse: true }
)
I have like result:
{
"_id": {
"Shop": "FirstShopNameCovered"
},
"isLinkedTo": [{
"PERSON": "Carleen",
"CITY": "Rome",
"ROOM": "Kitchen",
"STYLEPREFERED": "Modern",
"hasDonated": {
"DATE": "2019-10-11",
"OBJECT": "Set of dishes",
"COST": 72,
"COLOR": "White",
"PAYMENT": "Credit card"
}
}, {
"PERSON": "Carleen",
"CITY": "Rome",
"ROOM": "Kitcher",
"STYLEPREFERED": "Modern",
"hasDonated": {
"DATE": "2018-10-26",
"OBJECT": "Set of chairs",
"COST": 353,
"COLOR": "Grey",
"PAYMENT": "Coupon"
}
}, {
"PERSON": "Pernick",
"CITY": "Venezia",
"ROOM": "Bathroom",
"STYLE": "Minimalist",
"hasDonated": {
"DATE": "2018-09-18",
"OBJECT": "Mirror",
"COST": 68,
"COLOR": "Brown",
"PAYMENT": "Credit card"
}
}
You can see that there is replicated the Person "PERSON": "Carleen" with all data with 2 different arrays hasDonated.
I wish have something like this result, with person not replicated that contains all hasDonated arrays where he is present:
"_id": {
"Shop": "NameCovered"
},
"isLinkedTo": [{
"PERSON": "Carleen",
"CITY": "Rome",
"ROOM": "Kitchen",
"STYLE": "Retrò",
"hasDonated": {
"DATE": "2019-10-11",
"OBJECT": "Set of dishes",
"COST": 72,
"COLOR": "White",
"PAYMENT": "Credit card"
},
{
"DATE": "2018-10-26",
"OBJECT": "Chair",
"COST": 53,
"COLOR": "Grey",
"PAYMENT": "Coupon"
}
}, {
"PERSON": "Pernick",
"CITY": "Venezia",
"ROOM": "Bathroom",
"STYLE": "Minimalist",
"hasDonated": {
"DATE": "2018-09-18",
"OBJECT": "Mirror",
"COST": 68,
"COLOR": "Brown",
"PAYMENT": "Credit card"
}
How can I do to have the result like this?

Answer 1

First we need to $unwind to flat the array. Then group the hasDonated using $group where unique is found by combination of "_id" and "PERSON" as you mentioned.
[
{
"$unwind": "$isLinkedTo"
},
{
$group: {
_id: {
_id: "$_id",
per: "$isLinkedTo.PERSON"
},
isLinkedTo: {
$first: {
PERSON: "$isLinkedTo.PERSON",
CITY: "$isLinkedTo.CITY",
ROOM: "$isLinkedTo.ROOM",
STYLEPREFERED: "$isLinkedTo.STYLEPREFERED"
}
},
hasDonated: {
$addToSet: "$isLinkedTo.hasDonated"
}
}
},
{
$addFields: {
_id: "$_id._id",
"isLinkedTo.hasDonated": "$hasDonated"
}
},
{
$project: {
hasDonated: 0
}
},
{
$group: {
_id: "$_id",
isLinkedTo: {
$push: "$isLinkedTo"
}
}
}
]
Working Mongo playground