How to use mongoDB aggregartion in server side nodejs function? - node.js

Question

I am new to nodejs, I am trying to get the all duplicate documents in a collection in mongoDB for that I have tried the following query in mongo shell
db.collection.aggregate([
{
$group: {
_id: {
ProductName: "$ProductName"
},
uniqueIds: {
$addToSet: "$_id"
},
count: {
$sum: 1
}
}
},
{
$match: {
count: {
$gte: 2
}
}
},
{
$sort: {
count: -1
}
}
])
In mongo shell result:
{
"_id" : {
"ProductName" : "Sony Mobile"
},
"uniqueIds" : [
ObjectId("5728ce42a069270e00e59910"),
ObjectId("5728cde6a069270e00e5990e")
],
"count" : 2
},
{
"_id" : {
"ProductName" : "Nokia Mobile"
},
"uniqueIds" : [
ObjectId("5728ce42a069270e00e59920"),
ObjectId("5728cde6a069270e00e5990f")
],
"count" : 2
}
In mongo shell it gaves the result what i want correctly, but i tried the same query in nodejs server side function like below
Company.aggregate([
{
$group: {
_id: {
Proname: "$Proname"
},
uniqueIds: {
$addToSet: "$_id"
},
count: {
$sum: 1
}
}
},
{
$match: {
count: {
$gte: 2
}
}
},
{
$sort: {
count: -1
}
}
]).then(function (dupProds) {
console.log("ALL DUPLICATE PRDCTS : " + JSON.stringify(dupProds));
})
};
It shows me an error that Compnay.aggregate(...).then is not a function, I tried in different ways but no use, now how can get the result same as like I got in mongoshell.

Answer 1

Use exec instead of then for mongoose and in callback function parameters error then result.
Company.aggregate([
{
$group: {
_id: {
Proname: "$Proname"
},
uniqueIds: {
$addToSet: "$_id"
},
count: {
$sum: 1
}
}
},
{
$match: {
count: {
$gte: 2
}
}
},
{
$sort: {
count: -1
}
}
]).exec(function (err,dupProds) {
if(err) {
// return err;
}
console.log("ALL DUPLICATE PRDCTS : ", dupProds);
// return dupProds
})
};
Actually then worked on promise so if you want to use then you need to promising. so can use like
aggregate([{..}]).exec().then(function(result){..})
where aggregate([{..}]).exec() return promise

Answer 2

You need call exec before then:
Company.aggregate(params).exec().then(function (dupProds) {
console.log("ALL DUPLICATE PRDCTS : " + JSON.stringify(dupProds));
})
};
[ http://mongoosejs.com/docs/api.html#aggregate_Aggregate-exec ]