Mongoose aggregate returning empty result [duplicate] - node.js

Question

This question already has answers here:
Moongoose aggregate $match does not match id's
(5 answers)
Closed 3 years ago.
I have problems with a mongoose aggregate request.
It's kind of driving me crazy cause I can't find a solution anywhere. I would be very grateful for any support.
The schema:
var EvalSchema = new Schema({
modified: {type: Date, default: Date.now},
created : {type: Date, default: Date.now},
username: {type: String, required: true},
item: {type: String, required: true},
criteria: [{
description: {
type: String
},
eval: {
type: Number
}
}]
});
mongoose.model('Eval', EvalSchema);
and I'm using an aggregation to compute the sum of evaluations for each criterion for a given item.
Eval.aggregate([{
$match: {
item: item.id
}
}, {
$unwind: "$criteria"
}, {
$group: {
_id: "$criteria.description",
total: {
$sum: "$criteria.eval"
},
count: {
$sum: 1
}
}
}, {
$project: {
total: 1,
count: 1,
value: {
$divide: ["$total", "$count"]
}
}
}], function(err, result) {
if (err) {
console.log(err);
}
console.log(result);
});
Result is always empty....
I'm logging all queries that mongoose fire in the application. When I run the query in Mongodb, it returns the correct result.
coll.aggregate([{
'$match': {
item: 'kkkkkkkkkkk'
}
}, {
'$unwind': '$criteria'
}, {
'$group': {
_id: '$criteria.description',
total: {
'$sum': '$criteria.eval'
},
count: {
'$sum': 1
}
}
}, {
'$project': {
total: 1,
count: 1,
value: {
'$divide': ['$total', '$count']
}
}
}])
Result:
{
result: [{
"_id": "Overall satisfaction",
"total": 4,
"count": 1,
"value": 4
}, {
"_id": "service",
"total": 3,
"count": 1,
"value": 3
}, {
"_id": "Quality",
"total": 2,
"count": 1,
"value": 2
}, {
"_id": "Price",
"total": 1,
"count": 1,
"value": 1
}],
ok: 1
}
The model is referencing the correct collection.
Thank you :)

Answer 1

Your item.id in the $match function is a String, therefore you will need to convert it to an ObjectID, like so:
$match: { item: mongoose.Types.ObjectId(item.id) }
You can refer to this issue on GitHub aggregate for more details.