Undo Unwind in aggregate in mongodb - node.js

Question

I have multiple data something like this
{
"_id" : ObjectId("57189fcd72b6e0480ed7a0a9"),
"venueId" : ObjectId("56ce9ead08daba400d14edc9"),
"companyId" : ObjectId("56e7d62ecc0b8fc812b2aac5"),
"cardTypeId" : ObjectId("56cea8acd82cd11004ee67a9"),
"matchData" : [
{
"matchId" : ObjectId("57175c25561d87001e666d12"),
"matchDate" : ISODate("2016-04-08T18:30:00.000Z"),
"matchTime" : "20:00:00",
"_id" : ObjectId("57189fcd72b6e0480ed7a0ab"),
"active" : 3,
"cancelled" : 0,
"produced" : 3
},
{
"matchId" : ObjectId("57175c25561d87001e666d13"),
"matchDate" : ISODate("2016-04-09T18:30:00.000Z"),
"matchTime" : "20:00:00",
"_id" : ObjectId("57189fcd72b6e0480ed7a0aa"),
"active" : null,
"cancelled" : null,
"produced" : null
}
],
"__v" : 0
}
i m doing group by companyId and its work fine But i want to search in matchData based on matchtime and matchId For that purpose i am $unwind matchData after unwind i using my search query like this
db.getCollection('matchWiseData').aggregate([
{"$match":{
"matchData.matchId":{"$in":[ObjectId("57175c25561d87001e666d12")]}
}},
{"$unwind":"$matchData"},
{"$match":{
"matchData.matchId":{"$in":[ObjectId("57175c25561d87001e666d12")]}}
}])
its give me proper result but after applying unwind is there any way to undo it I m using unwind to just search inside subdocument or there is any other way to search inside subdocument.

Answer 1

Well you can of course just use $push and $first in a $group to get the document back to what it was:
db.getCollection('matchWiseData').aggregate([
{ "$match":{
"matchData.matchId":{"$in":[ObjectId("57175c25561d87001e666d12")]}
}},
{ "$unwind":"$matchData"},
{ "$match":{
"matchData.matchId":{"$in":[ObjectId("57175c25561d87001e666d12")]}
}},
{ "$group": {
"_id": "$_id",
"venueId": { "$first": "$venueId" },
"companyId": { "$first": "$companyId" },
"cardTypeId": { "$first": "$cardTypeId" },
"matchData": { "$push": "$matchData" }
}}
])
But you probably should have just used $filter with MongoDB 3.2 in the first place:
db.getCollection('matchWiseData').aggregate([
{ "$match":{
"matchData.matchId":{"$in":[ObjectId("57175c25561d87001e666d12")]}
}},
{ "$project": {
"venueId": 1,
"companyId": 1,
"cardTypeId": 1,
"matchData": {
"$filter": {
"input": "$matchData",
"as": "match",
"cond": {
"$or": [
{ "$eq": [ "$$match.matchId", ObjectId("57175c25561d87001e666d12") ] }
]
}
}
}
}}
])
And if you had at least MongoDB 2.6, you still could have used $map and $setDifference instead:
db.getCollection('matchWiseData').aggregate([
{ "$match":{
"matchData.matchId":{"$in":[ObjectId("57175c25561d87001e666d12")]}
}},
{ "$project": {
"venueId": 1,
"companyId": 1,
"cardTypeId": 1,
"matchData": {
"$setDifference": [
{ "$map": {
"input": "$matchData",
"as": "match",
"in": {
"$cond": [
{ "$or": [
{ "$eq": [ "$$match.matchId", ObjectId("57175c25561d87001e666d12") ] }
]},
"$$match",
false
]
}
}},
[false]
]
}
}}
])
That's perfectly fine when every array element already has a "unique" identifier, so the "set" operation just removes the false values from $map.
Both of those a ways to "filter" content from an array without actually using $unwind
N.B: Not sure if you really grasp that $in is used to match a "list of conditions" rather than being required to match on arrays. So generally the condition can just be:
"matchData.matchId": ObjectId("57175c25561d87001e666d12")
Where you only actually have a single value to match on. You use $in and $or when you have a "list" of conditions. Arrays themselves make no difference to the operator required.