MongoDB Aggregation: How to check if an object containing multiple properties exists in an array - mongodb

Question

I have an array of objects and I want to check if there is an object that matches multiple properties. I have tried using $in and $and but it does not work the way I want it to.
Here is my current implementation.
I have an array like
"choices": [
{
"name": "choiceA",
"id": 0,
"l": "k"
},
{
"name": "choiceB",
"id": 1,
"l": "j"
},
{
"name": "choiceC",
"id": 2,
"l": "l"
}
]
I am trying to write aggregation code that can check if there is an object that contains both "id":2 and "l":"j" properties. My current implementation checks if there is an object containing the first property then checks if there is an object containing the second one.
How can I get my desired results?
Below, see my aggregation query. The full code is here
db.poll.aggregate([
{
"$match": {
"_id": 100
}
},
{
$project: {
numberOfVotes: {
$and: [
{
$in: [
2,
"$choices.id"
]
},
{
$in: [
"j",
"$choices.l"
]
}
]
},
}
}
])
The above query returns true yet there is no object in the array both of the properties id:2 and "l":"J". I know the code works as expected. How can I get my desired results?

Answer 1

You want to use something like $elemMatch
db.collection.find({
choices: {
$elemMatch: {
id: 2,
l: "j"
}
}
})
MongoPlayground
EDIT
In an aggregation $project stage I would use $filter
db.poll.aggregate([
{
"$match": {
"_id": 100
}
},
{
$project: {
numberOfVotes: {
$gt: [
{
$size: {
$filter: {
input: "$choices",
as: "choice",
cond: {
$and: [
{
$eq: [
"$$choice.id",
2
]
},
{
$eq: [
"$$choice.l",
"j"
]
}
]
}
}
}
},
0
]
}
}
}
])
MongoPlayground