How to group an array of subdocuments by multiple fields? - arrays

Question

I have spent the better part of the day on this and am now out of ideas. Here is my collection:
[
{
"_id": "ID_XXX",
"logs": [
{
"lead_id": 123,
"list_id": "list_44",
"order_id": "order_1"
},
{
"lead_id": 124,
"list_id": "list_44",
"order_id": "order_2"
}
]
},
{
"_id": "ID_YYY",
"logs": [
{
"lead_id": 125,
"list_id": "list_44",
"order_id": "order_2"
},
{
"lead_id": 126,
"list_id": "list_44",
"order_id": "order_2"
},
{
"lead_id": 127,
"list_id": "list_44",
"order_id": "order_3"
},
{
"lead_id": 128,
"list_id": "list_66",
"order_id": "order_3"
}
]
}
]
I'm just trying to get the counts for list_id and order_id while preserving the _id of the document they are in. Here is my desired output:
[
{
"_id": "ID_XXX",
"counts": [
{
"lists": {"list_44": 2},
},
{
"orders": {"order_1": 1, "order_2": 1}
}
]
},
{
"_id": "ID_YYY",
"counts": [
{
"lists": {"list_44": 3, "list_66": 1},
},
{
"orders": {"order_2": 2, "order_3": 2}
}
]
}
]
I have tried way too many aggregate variations to list here, but the latest is this:
db.collection.aggregate([
{
$unwind: "$logs"
},
{
$group: {
_id: "$_id",
lists: {
$push: "$logs.list_id"
},
orders: {
$push: "$logs.order_id"
}
}
}
])
Which does not give me what I want. Can anyone point me in the right direction? Here is the playground link: https://mongoplayground.net/p/f-jk7lbSrJ0

Answer 1

$reduce to iterate loop of logs, convert logs object to array in k(key) v(value) format using $objectToArray, $concatArrays with initialValue in $reduce,
$filter above reduce result as input and filter required fields from logs
$unwind deconstruct logs array
db.collection.aggregate([
{
$addFields: {
logs: {
$filter: {
input: {
$reduce: {
input: "$logs",
initialValue: [],
in: { $concatArrays: ["$$value", { $objectToArray: "$$this" }] }
}
},
cond: { $in: ["$$this.k", ["list_id", "order_id"]] }
}
}
}
},
{ $unwind: "$logs" },
$group by _id and logs object and get the total count using $sum
{
$group: {
_id: {
_id: "$_id",
logs: "$logs"
},
counts: { $sum: 1 }
}
},
$group by _id and make lists array if logs.k is list_id and return in k and v format otherwise $$REMOVE, same as for orders make an array of order on the base of order_id
$addFields to convert lists array from k and v format to object format using $arrayToObjectand same as fororders` array
{
$group: {
_id: "$_id._id",
lists: {
$push: {
$cond: [
{ $eq: ["$_id.logs.k", "list_id"] },
{
k: "$_id.logs.v",
v: "$counts"
},
"$$REMOVE"
]
}
},
orders: {
$push: {
$cond: [
{ $eq: ["$_id.logs.k", "order_id"] },
{
k: "$_id.logs.v",
v: "$counts"
},
"$$REMOVE"
]
}
}
}
},
{
$addFields: {
lists: { $arrayToObject: "$lists" },
orders: { $arrayToObject: "$orders" }
}
}
])
Playground