MongoDB $cond with embedded document array - mongodb

Question

I am trying to generate a new collection with a field 'desc' having into account a condition in field in a documment array. To do so, I am using $cond statement
The origin collection example is the next one:
{
"_id" : ObjectId("5e8ef9a23e4f255bb41b9b40"),
"Brand" : {
"models" : [
{
"name" : "AA"
},
{
"name" : "BB"
}
]
}
}
{
"_id" : ObjectId("5e8ef9a83e4f255bb41b9b41"),
"Brand" : {
"models" : [
{
"name" : "AG"
},
{
"name" : "AA"
}
]
}
}
The query is the next:
db.runCommand({
aggregate: 'cars',
'pipeline': [
{
'$project': {
'desc': {
'$cond': {
if: {
$in: ['$Brand.models.name',['BB','TC','TS']]
},
then: 'Good',
else: 'Bad'
}
}
}
},
{
'$project': {
'desc': 1
}
},
{
$out: 'cars_stg'
}
],
'allowDiskUse': true,
})
The problem is that the $cond statement is always returning the "else" value. I also have tried $or statement with $eq or the $and with $ne, but is always returning "else".
What am I doing wrong, or how should I fix this?
Thanks

Answer 1

Since $Brand.models.name returns an array, we cannot use $in operator.
Instead, we can use $setIntersection which returns an array that contains the elements that appear in every input array
db.cars.aggregate([
{
"$project": {
"desc": {
"$cond": [
{
$gt: [
{
$size: {
$setIntersection: [
"$Brand.models.name",
[
"BB",
"TC",
"TS"
]
]
}
},
0
]
},
"Good",
"Bad"
]
}
}
},
{
"$project": {
"desc": 1
}
},
{
$out: 'cars_stg'
}
])
MongoPlayground | Alternative $reduce