How to flatten an array after db call in express? - arrays

Question

I am using express to query my mongodb database using the native driver (not Mongoose.)
I am trying to do some data clean up after a MongoDB response. I don't mind if this could be achieved with MongoDB's aggregation query or some variation of it, for completeness the current query I'm using is: collection.find({'make.name': req.params.make}, {'model.name': 1, 'submodel.body': 1, '_id': 0}).toArray();
I have a response from mongodb:
[
{
"model" : {
"name" : "3 Series"
},
"submodel" : {
"body" : "Convertible"
}
},
{
"model" : {
"name" : "3 Series"
},
"submodel" : {
"body" : "Coupe"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Coupe"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Coupe"
}
},
{
"model" : {
"name" : "3 Series"
},
"submodel" : {
"body" : "Coupe"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Convertible"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Convertible"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Convertible"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Coupe"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Coupe"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Coupe"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Convertible"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Convertible"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Convertible"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Coupe"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Convertible"
}
},
{
"model" : {
"name" : "2 Series"
},
"submodel" : {
"body" : "Coupe"
}
}
]
which I would like to simplify to this:
[
"model" : {
"name": "2 Series"
}
"submodel" : {
"body": ["Convertible", "Coupe"]
}
"model" : {
"name": "3 Series"
}
"submodel" : {
"body": ["Convertible", "Coupe"]
}
]
New output:
{ "_id" : "M3", "submodel" : [ "Sedan" ] }
{ "_id" : "X5 eDrive", "submodel" : [ "SUV" ] }
{ "_id" : "X5 M", "submodel" : [ "SUV" ] }
{ "_id" : "M4 GTS", "submodel" : [ "Coupe" ] }
{ "_id" : "ActiveHybrid 5", "submodel" : [ "Sedan" ] }
{ "_id" : "X5", "submodel" : [ "SUV" ] }
{ "_id" : "X6 M", "submodel" : [ "SUV" ] }
{ "_id" : "i8", "submodel" : [ "Coupe" ] }
{ "_id" : "X4", "submodel" : [ "SUV" ] }
{ "_id" : "5 Series Gran Turismo", "submodel" : [ "Hatchback" ] }
{ "_id" : "M4", "submodel" : [ "Coupe", "Convertible" ] }
{ "_id" : "5 Series", "submodel" : [ "Sedan" ] }
{ "_id" : "M6 Gran Coupe", "submodel" : [ "Sedan" ] }
{ "_id" : "X1", "submodel" : [ "SUV" ] }
{ "_id" : "3 Series eDrive", "submodel" : [ "Sedan" ] }
{ "_id" : "2 Series", "submodel" : [ "Coupe", "Convertible" ] }
{ "_id" : "6 Series Gran Coupe", "submodel" : [ "Sedan" ] }
{ "_id" : "3 Series", "submodel" : [ "Wagon", "Sedan" ] }
{ "_id" : "Z4", "submodel" : [ "Convertible" ] }
{ "_id" : "6 Series", "submodel" : [ "Convertible", "Coupe" ] }
new output:
{
"_id": "2 Series",
"submodel": [
"Coupe",
"Convertible"
]
},
{
"_id": "3 Series",
"submodel": [
"Wagon",
"Sedan"
]
},
{
"_id": "3 Series Gran Turismo",
"submodel": [
"Hatchback"
]
},
{
"_id": "3 Series eDrive",
"submodel": [
"Sedan"
]
},
{
"_id": "4 Series",
"submodel": [
"Coupe",
"Convertible"
]
},
As you can see, model.name is a unique property, and "submodel.body" is now an array of unique body types.
How can I convert my array of non-unique models, to an array of unique models?
Current Query:
router.get('/test/:make', (req, res) => {
var collection = db.get().collection('styles');
collection.aggregate({
$match: {
$or: [{
"make.niceName": req.params.make
},
{
"make.name": req.params.make
}
]
}
}, {
$group: {
_id: "$model.name",
"submodels": {
$addToSet: "$submodel.body"
}
}
}, {
$sort: {
_id: 1
}
}, {
$project: {
models: "$_id",
submodel: 1,
_id: 0
}
}).toArray((err, docs) => {
res.send(docs)
})

Answer 1

You can try below aggregation pipeline. $addToSet to get distinct submodel in each model group.
collection.aggregate({
$match: {
"make.name": req.params.make
}
}, {
$group: {
_id: "$model.name",
submodel: {
$addToSet: "$submodel.body"
}
}
}, {
$sort: {
_id: 1
}
}, {
$project: {
models: "$_id",
submodel: 1,
_id: 0
}
})