adding rank based on sorting mongodb aggregate unwind - database

Question

I am using includeArrayIndex to add the rank based on sorting
Here is the aggregation query
dbo.collection("funds").aggregate([
{
"$sort": {
"amount": -1
}
},
{
"$group": {
"_id": "",
"items": {
"$push": "$$ROOT"
}
}
},
{
"$unwind": {
"path": "$items",
"includeArrayIndex": "items.rank"
}
},
{
"$replaceRoot": {
"newRoot": "$items"
}
},
{
"$sort": {
"rank": -1
}
}
])
and this assign the rank field but starting from 0, is there any way to start it from 1
tried with set like this
[
{
'$sort': {
'amount': -1
}
}, {
'$group': {
'_id': '',
'items': {
'$push': '$$ROOT'
}
}
}, {
'$unwind': {
'path': '$items',
'includeArrayIndex': 'items.rank'
}
}, {
'$replaceRoot': {
'newRoot': '$items'
}
},
{
'$set': {
'rank': {
'$add': [
'$rank', 1
]
}
}
},
// {
// '$sort': {
// 'rank': 1
// }
// }
]
in the mongodb compass aggregation tab it shows that field got added but when i run this script using nodejs it does not add the rank field
even i tried with
const a = await dbo.collection("funds").aggregate(
[
{
'$sort': {
'amount': 1
}
}, {
'$group': {
'_id': '',
'items': {
'$push': '$$ROOT'
}
}
}, {
'$unwind': {
'path': '$items',
'includeArrayIndex': 'items.rank'
}
}, {
'$replaceRoot': {
'newRoot': '$items'
}
},
{
'$addFields': {
'rank': {
'$add': [
'$rank', 1
]
}
}
}
]
).toArray();
and this even prints on console as a
[
{ _id: new ObjectId("6220d2fe20e33d48c865b720"), amount: 1, rank: 1 },
{
_id: new ObjectId("6220d2cf20e33d48c865b71e"),
amount: 10,
rank: 2
},
{
_id: new ObjectId("6220d2f520e33d48c865b71f"),
amount: 12,
rank: 3
}
]
and then tried with $setWindowFields
dbo.collection("funds").aggregate( [
{
$setWindowFields: {
sortBy: { amount: -1 },
output: {
rank: {
$rank: {}
}
}
}
}
] )
but it shows
err MongoServerError: Unrecognized pipeline stage name: '$setWindowFields'
Sample document is like
[
{amount : 20, name :""},
{amount : 22, name :""}
]

Answer 1

Not sure if this was already answered. But you just have to add { $out: "funds" }
at the last of your code. PFB the working code ...
const a = await dbo.collection("funds").aggregate(
[
{
'$sort': {
'amount': 1
}
}, {
'$group': {
'_id': '',
'items': {
'$push': '$$ROOT'
}
}
}, {
'$unwind': {
'path': '$items',
'includeArrayIndex': 'items.rank'
}
}, {
'$replaceRoot': {
'newRoot': '$items'
}
},
{
'$addFields': {
'rank': {
'$add': [
'$rank', 1
]
}
}
},
{ $out: "funds" }
], {allowDiskUse:true}
).toArray();