MongoDB Querying Nested Arrays - arrays

Question

I'm having some trouble with querying a Mongo Collection.
I have a Collection like this:
{
"_id" : "555bd34329de3cf232434ef2",
"cars" : [
{
"0" : {
"parts" : [
{
"name" : "x1",
"price" : 12
},
{
"name" : "x2",
"price" : 14
}
]
},
"1" : {
"parts" : [
{
"name" : "y1",
"price" : 8
},
{
"name" : "y2",
"price" : 12
}
]
}
}
]
}
I'd like to return just the following:
"parts" : [
{
"name" : "x1",
"price" : 12
},
{
"name" : "x2",
"price" : 14
}
]
In other words, I need to figure out how to query the Collection by two parameters at the same time:
where the ID matches "555bd34329de3cf232434ef2"
where the "name" of the part matches "x1"
Does anyone know how to do this kind of nested query?

Answer 1

Assuming a document structure like this:
{
"_id" : ObjectId("555bd34329de3cf232434ef2"),
"cars" : [
{
"parts" : [
{
"name" : "x1",
"price" : 12
},
{
"name" : "x2",
"price" : 14
}
]
},
{
"parts" : [
{
"name" : "y1",
"price" : 8
},
{
"name" : "y2",
"price" : 12
}
]
}
]
}
you can run the following query:
db.collection.find({ "_id": ObjectId("555bd34329de3cf232434ef2"), "cars.parts.name" : "x1" }, { "_id": 0, "cars.$": 1 })
which will get you pretty close to where you want to be:
{
"cars" : [
{
"parts" : [
{
"name" : "x1",
"price" : 12
},
{
"name" : "x2",
"price" : 14
}
]
}
]
}
You could get closer using the aggregation framework if that's not good enough...