Find objects in deep Mongo DB docs - node.js

Question

I've got a Mongo DB doc with a teams array. All the objects in the teams array contain a user_ids array. How do I find all documents containing a team where user_ids contains a specific Object Id? I'm using Mongoose with Node.
This is the doc structure. How would I eg find all docs with Object Id "56a60da2351195cc6be83799" in any of the teams?
{
"_id" : ObjectId("56a60da3351195cc6be8379c"),
"session_id" : ObjectId("56a60da2351195cc6be83798"),
"teams" : [
{
"score" : 0,
"user_ids" : [
ObjectId("56a60da2351195cc6be83799")
]
},
{
"score" : 0,
"user_ids" : [
ObjectId("56a60da2351195cc6be8379a")
]
}
],
"created_at" : ISODate("2016-01-25T11:57:23.006Z") }
Thanks

Answer 1

Let's say your collection name is collection, try:
db.collection.find({"teams.user_ids": ObjectId("56a60da2351195cc6be83799")})
It will find a document, if exists matching user_ids

Answer 2

For nested arrays the $in operator will be a good choice (see documentation).
I tried to reproduce your settings and created a simple model:
var testSchema = mongoose.Schema({
session_id: { type: Number },
teams : [
{
score: { type: Number },
user_ids: [{ type: Number }]
}
]
})
var Test = mongoose.model("Test", testSchema);
Inserted demo data:
var test1 = new Test({
session_id: 5,
teams: [
{ score: 5, user_ids: [ 1, 2, 4] },
{ score: 3, user_ids: [ 2, 7, 9 ] },
{ score: 1, user_ids: [ 3 ] },
]
});
test1.save(function(err, t1) { console.log("test", err, t1); });
var test2 = new Test({
session_id: 1,
teams: [
{ score: 5, user_ids: [ 11, 12 ] },
{ score: 3, user_ids: [ 1, 9 ] },
]
});
test2.save(function(err, t2) { console.log("test", err, t2); });
The query to get all objects with a userId of 2 would look like:
Test.find({ "teams.user_ids": { $in: [2] }}, function(err, res) {
console.log("query:", err, res);
});
Or in a more mongoose way of reassembling queries:
Test.find()
.where('teams.user_ids')
.in([2])
.then(result => { console.log(result); })
.catch(err => { console.log(err); });