MongoDB: Get all $matched elements individually from an array - mongodb

Question

I'm trying to get all matched elements individually, here is the sample data and the query.
// json
[
{
"name": "Mr Cool",
"ican": [
{
"subcategory": [
{
"id": "5bffdba824488b182ec86f8d", "name": "Cricket"
},
{
"id": "5bffdba824488b182ec86f8c", "name": "Footbal"
}
],
"category": "5bffdba824488b182ec86f88",
"name": "Sports"
}
]
}
]
// query
db.collection.aggregate([
{
"$match": {
"ican.subcategory.name": { $in: ["Cricket","Football"] }
}
},
{
"$project": { "_id": 1, "name": 1, }
}
])
I'm getting the combined result, I need the individual match record. I tried $all and $elementMatch but getting the same response. how can I get the results as below. I'm using $aggregate because I will be using $geoNear pipeline for getting the nearby users.
// current result
[
{
"_id": ObjectId("5a934e000102030405000000"),
"name": "Mr Cool"
}
]
// expected result
[
{
"_id": ObjectId("5a934e000102030405000000"),
"name": "Mr Cool",
"subcategory: "Cricket"
},
{
"_id": ObjectId("5a934e000102030405000000"),
"name": "Mr Cool",
"subcategory: "Footbal"
}
]
Thank you

Answer 1

Try this Mongo Playground
db.col.aggregate([
{"$unwind" : "$ican"},
{"$unwind" : "$ican.subcategory"},
{"$match" : {"ican.subcategory.name": { "$in": ["Cricket","Football"] }}},
{"$group" : {"_id" : null,"data" : {"$push" : {"_id" : "$_id","name" : "$name","subcategory" : "$ican.subcategory.name"}}}},
{"$unwind" : "$data"},
{"$replaceRoot" : {"newRoot" : "$data"}}
])

Answer 2

You can use below aggregation without the $unwind and for better performance
db.collection.aggregate([
{ "$match": { "ican.subcategory.name": { "$in": ["Cricket","Football"] }}},
{ "$project": {
"ican": {
"$reduce": {
"input": "$ican",
"initialValue": [],
"in": {
"$concatArrays": [
{ "$filter": {
"input": {
"$map": {
"input": "$$this.subcategory",
"as": "s",
"in": { "name": "$name", "subcategory": "$$s.name" }
}
},
"as": "fil",
"cond": { "$in": ["$$fil.subcategory", ["Football"]] }
}},
"$$value"
]
}
}
}
}},
{ "$unwind": "$ican" },
{ "$replaceRoot": { "newRoot": "$ican" }}
])