mongoose 4.7.5: how to fetch subdocuments in array - node.js

Question

Am trying to fetch and filter subdocuments in array.
The document has this structure:
{
"_id": {
"$oid": "58bc4fa0fd85f439ee3ce716"
},
"updatedAt": {
"$date": "2017-03-08T20:39:19.390Z"
},
"createdAt": {
"$date": "2017-03-05T17:49:20.455Z"
},
"app": {
"$oid": "58ae10852035431d5a746cbd"
},
"stats": [
{
"meta": {
"key": "value",
"key": "value"
},
"_id": {
"$oid": "58bc4fc4fd85f439ee3ce718"
},
"data": "data",
"updatedAt": {
"$date": "2017-03-05T17:49:56.305Z"
},
"createdAt": {
"$date": "2017-03-05T17:49:56.305Z"
}
},
{
"meta": {
"key": "value",
"key": "value"
},
"_id": {
"$oid": "58c06bf79eaf1f15aafe39d0"
},
"data": "data",
"updatedAt": {
"$date": "2017-03-08T20:39:19.391Z"
},
"createdAt": {
"$date": "2017-03-08T20:39:19.391Z"
}
}
]
}
What i want to get is the subdocuments in the stats array between two dates
I tried mongoose queries chain:
Model.findById(id)
.select('stats')
.where('stats.createdAt').gt(data-value).lt(data-value)
But the result always the full document including the all the subdocuments.
Also I tried aggregation like this:
Model.aggregate({
$match: {
'stats.createdAt': '2017-03-05T17:49:56.305Z'
}
})
The result is always null

Answer 1

Your result is null because '2017-03-05T17:49:56.305Z' is a String, you are looking for a Date : new Date('2017-03-05T17:49:56.305Z')
You can filter subdocuments with a date range with $unwind and $match :
var startDate = new Date('2017-03-05T17:49:56.305Z');
var endDate = new Date('2017-03-08T17:49:56.305Z');
Model.aggregate([{
$match: {
"_id": new mongoose.mongo.ObjectId("58bc4fa0fd85f439ee3ce716"),
"stats.createdAt": {
$gte: startDate,
$lt: endDate
}
}
}, {
$unwind: "$stats"
}, {
$match: {
"stats.createdAt": {
$gte: startDate,
$lt: endDate
}
}
}], function(err, res) {
console.log(res);
})
Or more straightforward with $filter :
Model.aggregate([{
$match: {
"_id": new mongoose.mongo.ObjectId("58bc4fa0fd85f439ee3ce716"),
"stats.createdAt": {
$gte: startDate,
$lt: endDate
}
}
}, {
$project: {
"stats": {
$filter: {
input: "$stats",
as: "stat",
cond: {
$and: [
{ $gte: ["$$stat.createdAt", startDate] },
{ $lte: ["$$stat.createdAt", endDate)] }
]
}
}
}
}
}], function(err, res) {
console.log(res);
})