Modifying or Unwinding deep nested arrays with mongo query - mongodb

Question

After having made my own aggregation pipeline, I have arrived at the following result:
[
{
"_id": "53712c7238b8d900008ef71c",
"address": [
{
"_id": "53712c7238b8d900008ef71b",
"phoneNumber": "4092348294",
...
}
],
"name": "TestDealer",
"vehicles": [
{
"_id": "53712fa138b8d900008ef720",
"createdAt": "2014-05-12T20:08:00.000Z",
"tags": [
"vehicle"
],
"opts": [
{
"_id": "53712fa138b8d900008ef71e",
"hasSunroof": false,
...
}
],
"listed": true,
"disclosures": [
{
"_id": "53712fa138b8d900008ef71f",
"waterDamage": false,
...
}
],
"details": [
{
"_id": "53712fa138b8d900008ef71d",
"year": 2007,
...
}
]
},
{
"_id": "5373c6439058859af7904a17",
"createdAt": "2014-05-14T19:17:00.000Z",
"tags": [
"vehicle"
],
"opts": [
{
"_id": "5373c6439058859af7904a15",
"hasSunroof": false,
....
"other": []
}
],
"listed": true,
"disclosures": [
{
"_id": "5373c6439058859af7904a16",
"waterDamage": false,
...
}
],
"details": [
{
"_id": "5373c6439058859af7904a14",
"year": 2013,
...
}
]
}
]
}
]
As you can see, vehicles is an array of subdocuments (vehicles) that follow a specific schema:
details: an array of details subdocs
opts: an array of opts subdocs
disclosures: an array of disclosures subdocs
For each of details, disclosures and opts I would like to return the first subdoc in the array as opposed to an array. However, I'm not sure where to start. I can't really $unwind vehicles because it is possible that it might be empty.
Here's is what my final data should look like:
[
{
"_id": "53712c7238b8d900008ef71c",
"address": [
{
"_id": "53712c7238b8d900008ef71b",
"phoneNumber": "4092348294",
...
}
],
"name": "TestDealer",
"vehicles": [
{
"_id": "53712fa138b8d900008ef720",
"createdAt": "2014-05-12T20:08:00.000Z",
"tags": [
"vehicle"
],
"opts": {
"_id": "53712fa138b8d900008ef71e",
"hasSunroof": false,
...
},
"listed": true,
"disclosures": {
"_id": "53712fa138b8d900008ef71f",
"waterDamage": false,
...
},
"details": {
"_id": "53712fa138b8d900008ef71d",
"year": 2007,
...
}
},
{
"_id": "5373c6439058859af7904a17",
"createdAt": "2014-05-14T19:17:00.000Z",
"tags": [
"vehicle"
],
"opts": {
"_id": "5373c6439058859af7904a15",
"hasSunroof": false,
....
"other": []
},
"listed": true,
"disclosures": {
"_id": "5373c6439058859af7904a16",
"waterDamage": false,
...
},
"details": {
"_id": "5373c6439058859af7904a14",
"year": 2013,
...
}
}
]
}
]
EDIT:
Here is the aggregation I do to get my data (in CoffeeScript):
{
$match:
_id: ObjectId(params.id)
}
{
$unwind: '$inventories'
}
{
$match:
'inventories._id': 'active'
}
{
$redact:
$cond:
if:
$eq:['$listed',false]
then: '$$PRUNE'
else: '$$DESCEND'
}
{
$project:
address: 1
name: '$dealerName'
email: '$_id.email'
vehicles: '$inventories.vehicles'
}
As well as the original data:
{ "_id" : ObjectId( "53712c7238b8d900008ef71c" ),
"email" : "test#test.com",
"createdAt" : Date( 1399925280000 ),
"password" : "$2a$10$3dhicJuONkXeI9mQflXF0.JftAx7mLQaY2./6a3O7xdrs5qfH2zMW",
"firstName" : "TestName",
"lastName" : "testName",
"dealerName" : "TestDealer",
"dealerType" : "Franchised Dealer",
"emailIsVerified" : false,
"lastLoggedInAt" : Date( 1400247300000 ),
"expiresAt" : Date( 4524062882000 ),
"deletedAt" : null,
"updatedAt" : Date( 1400251500000 ),
"inventories" : [
{ "title" : "activeInventory",
"_id" : "active",
"vehicles" : [
{ "_id" : ObjectId( "53712fa138b8d900008ef720" ),
"createdAt" : Date( 1399925280000 ),
"tags" : [
"vehicle" ],
"opts" : [
{ "_id" : ObjectId( "53712fa138b8d900008ef71e" ),
"hasSunroof" : false,
"hasSnowTires" : false,
"hasPowerWindows" : false,
"hasNavigationSystem" : false,
"hasManuals" : false,
"hasMags" : false,
"hasLeather" : false,
"hasKeylessEntry" : false,
"hasHeatedSeats" : false,
"hasDvdSystem" : false,
"hasAirConditioning" : false,
"has2SetsOfKeys" : false,
"other" : [] } ],
"listed" : true,
"disclosures" : [
{ "_id" : ObjectId( "53712fa138b8d900008ef71f" ),
"waterDamage" : false,
"vehicleLien" : false,
"usVehicle" : false,
"totalLossByInsurer" : false,
"theftOrRecovery" : false,
"taxiOrLimo" : false,
"structuralPartsAreDamagedOrAlteredOrRepaired" : false,
"suspensionOrSubFrameNeedsRepair" : false,
"repainted" : false,
"previousDamageExceeding3k" : false,
"powerTrainNeedsRepair" : false,
"policeCruiser" : false,
"outOfProvinceOrState" : false,
"originalOwner" : false,
"originalManufacturerVinPlate" : false,
"originalSpecificationsChanged" : false,
"odometerRolledBackOrReplaced" : false,
"manufacturerWarrantyCancelled" : false,
"manufacturerBadgesChanged" : false,
"fuelSystemNeedsRepair" : false,
"fireDamage" : false,
"engineNeedsRepair" : false,
"emergencyVehicle" : false,
"electricalSystemNeedsRepair" : false,
"dailyRental" : false,
"computerNeedsRepair" : false,
"antiLockBrakesDamagedOrInoperable" : false,
"airbagIsMissingOrInoperable" : false,
"airConditioningNeedsRepair" : false } ],
"details" : [
{ "_id" : ObjectId( "53712fa138b8d900008ef71d" ),
"year" : 2007,
"vin" : "JN8AZ08W27W649264",
"trim" : "SE",
"transmission" : "Automatic",
"price" : 132123,
"model" : "Murano 4D Utility AWD",
"mileageReading" : 125000,
"make" : "Nissan",
"interiorColor" : "Black",
"history" : "Carproof Verified ($40.00)",
"hasAccident" : false,
"fuelType" : "Biodiesel",
"exteriorColor" : "Blue",
"driveTrain" : "FWD",
"description" : "dsadas",
"cylinders" : 4,
"mileageType" : "kms" } ] },
{ "_id" : ObjectId( "53713bfc1429925f0faf79d0" ),
"createdAt" : Date( 1399929780000 ),
"tags" : [
"vehicle" ],
"opts" : [
{ "_id" : ObjectId( "53713bfc1429925f0faf79ce" ),
"hasSunroof" : false,
"hasSnowTires" : false,
"hasPowerWindows" : false,
"hasNavigationSystem" : false,
"hasManuals" : false,
"hasMags" : false,
"hasLeather" : false,
"hasKeylessEntry" : false,
"hasHeatedSeats" : false,
"hasDvdSystem" : false,
"hasAirConditioning" : false,
"has2SetsOfKeys" : false,
"other" : [] } ],
"listed" : false,
"disclosures" : [
{ "_id" : ObjectId( "53713bfc1429925f0faf79cf" ),
"waterDamage" : false,
"vehicleLien" : false,
"usVehicle" : false,
"totalLossByInsurer" : false,
"theftOrRecovery" : false,
"taxiOrLimo" : false,
"structuralPartsAreDamagedOrAlteredOrRepaired" : false,
"suspensionOrSubFrameNeedsRepair" : false,
"repainted" : false,
"previousDamageExceeding3k" : false,
"powerTrainNeedsRepair" : false,
"policeCruiser" : false,
"outOfProvinceOrState" : false,
"originalOwner" : false,
"originalManufacturerVinPlate" : false,
"originalSpecificationsChanged" : false,
"odometerRolledBackOrReplaced" : false,
"manufacturerWarrantyCancelled" : false,
"manufacturerBadgesChanged" : false,
"fuelSystemNeedsRepair" : false,
"fireDamage" : false,
"engineNeedsRepair" : false,
"emergencyVehicle" : false,
"electricalSystemNeedsRepair" : false,
"dailyRental" : false,
"computerNeedsRepair" : false,
"antiLockBrakesDamagedOrInoperable" : false,
"airbagIsMissingOrInoperable" : false,
"airConditioningNeedsRepair" : false } ],
"details" : [
{ "_id" : ObjectId( "53713bfc1429925f0faf79cd" ),
"year" : 2007,
"vin" : "JN8AZ08W27W649264",
"trim" : "SE",
"transmission" : "Manual",
"price" : 13241234,
"model" : "Murano 4D Utility AWD",
"mileageReading" : 1312312,
"make" : "Mercedes-Benz",
"interiorColor" : "Black",
"history" : "Carproof Claims ($25.00)",
"hasAccident" : true,
"fuelType" : "Diesel",
"exteriorColor" : "Black",
"driveTrain" : "RWD",
"description" : "werwe",
"cylinders" : 4,
"mileageType" : "kms" } ] },
{ "_id" : ObjectId( "5373c6439058859af7904a17" ),
"createdAt" : Date( 1400095020000 ),
"tags" : [
"vehicle" ],
"opts" : [
{ "_id" : ObjectId( "5373c6439058859af7904a15" ),
"hasSunroof" : false,
"hasSnowTires" : false,
"hasPowerWindows" : false,
"hasNavigationSystem" : false,
"hasManuals" : false,
"hasMags" : false,
"hasLeather" : false,
"hasKeylessEntry" : false,
"hasHeatedSeats" : false,
"hasDvdSystem" : false,
"hasAirConditioning" : false,
"has2SetsOfKeys" : false,
"other" : [] } ],
"listed" : true,
"disclosures" : [
{ "_id" : ObjectId( "5373c6439058859af7904a16" ),
"waterDamage" : false,
"vehicleLien" : false,
"usVehicle" : false,
"totalLossByInsurer" : false,
"theftOrRecovery" : false,
"taxiOrLimo" : false,
"structuralPartsAreDamagedOrAlteredOrRepaired" : false,
"suspensionOrSubFrameNeedsRepair" : false,
"repainted" : false,
"previousDamageExceeding3k" : false,
"powerTrainNeedsRepair" : false,
"policeCruiser" : false,
"outOfProvinceOrState" : false,
"originalOwner" : false,
"originalManufacturerVinPlate" : false,
"originalSpecificationsChanged" : false,
"odometerRolledBackOrReplaced" : false,
"manufacturerWarrantyCancelled" : false,
"manufacturerBadgesChanged" : false,
"fuelSystemNeedsRepair" : false,
"fireDamage" : false,
"engineNeedsRepair" : false,
"emergencyVehicle" : false,
"electricalSystemNeedsRepair" : false,
"dailyRental" : false,
"computerNeedsRepair" : false,
"antiLockBrakesDamagedOrInoperable" : false,
"airbagIsMissingOrInoperable" : false,
"airConditioningNeedsRepair" : false } ],
"details" : [
{ "_id" : ObjectId( "5373c6439058859af7904a14" ),
"year" : 2013,
"vin" : "12345678901234567",
"trim" : "SE",
"transmission" : "Automatic",
"price" : 13564,
"model" : "Red",
"mileageReading" : 13453,
"make" : "Daihatsu",
"interiorColor" : "Black",
"history" : "Carproof Verified ($40.00)",
"hasAccident" : true,
"fuelType" : "Diesel",
"exteriorColor" : "Black",
"driveTrain" : "FWD",
"description" : "wrw",
"cylinders" : 3,
"mileageType" : "kms" } ] } ],
"tags" : [
"inventory",
"active",
"vehicles" ] },
{ "title" : "soldInventory",
"_id" : "sold",
"vehicles" : [],
"tags" : [
"inventory",
"sold",
"vehicles" ] },
{ "title" : "deletedInventory",
"_id" : "deleted",
"vehicles" : [],
"tags" : [
"inventory",
"deleted",
"vehicles" ] } ],
"address" : [
{ "_id" : ObjectId( "53712c7238b8d900008ef71b" ),
"phoneNumber" : "4092348294",
"country" : "Canada",
"zip" : "301111",
"region" : "Quebec",
"city" : "Montreal",
"street2" : "Apt. 101",
"street1" : "1213 Street",
"additionalNumbers" : [] } ],
"__v" : 3 }

Answer 1

If you are using 2.6 (which you must be since you use $redact) and if the array is always guaranteed to be empty if there are no tags or opts, you can use this technique to make sure you don't lose vehicles which have empty arrays when you $unwind:
In a $project phase add the following for all arrays you want to $unwind to keep just the first element:
opts:{$cond:{if:{$eq:[{$size:"$opts"},0]}, then:{$literal:[ "none" ]}, else:"$opts"}}
For each sub-array you can now group keeping the first one, and then repeat again for the next sub-array.
You'll need to be careful about unwinding and re-grouping for each array separately to keep from ending up with any duplication, if you are not aggregating anything else, you can do it in a single group with as many $unwinds as there are sub-arrays.