Add sequence number to items from mongodb query - mongodb

Question

I have MongoDB collection items with following documents:
{ "name": "First", "value": 8 },
{ "name": "Second", "value": 2 },
{ "name": "Third", "value": 5 }
I would like to sort them by name or value and then add sequence number (index property) to each of them (first item will have "index": 1, second "index": 2, etc.). So for this query:
db.items.aggregate([{ $sort: { "value": 1 } }])
result should be:
{ "name": "Second", "value": 2, "index": 1 },
{ "name": "Third", "value": 5, "index": 2 },
{ "name": "First", "value": 8, "index": 3 }
This should also works with $skip. With { "$skip": 1 }, result should be items with indexes 2, 3, not 1, 2. Is there any way to do this using pure MongoDB, without any application logic?

Answer 1

Note: Inspired by #turvishal's answer to meet the below things
Index starting from 1
Skip the way OP wants
Mongo-play
db.collection.aggregate([
{
$sort: {
value: 1
}
},
{
$group: {
_id: 1,
items: {
$push: {
name: "$name",
value: "$value"
}
}
}
},
{
$unwind: {
path: "$items",
includeArrayIndex: "index"
}
},
{
$project: {
_id: 0,
name: "$items.name",
value: "$items.value",
index: { //Incrementing the index by 1
$add: [
"$index",
1
]
}
}
},
{ //Addition of skip
"$skip": 1
}
])

Answer 2

Might be this is one option you can do with includeArrayIndex in $unwind,
$sort by value that you already did
$group by name and value and push in items
$unwind deconstruct items and set field index in includeArrayIndex
$project required fields and increment index with because it start with 0 zero
db.collection.aggregate([
{ $sort: { value: 1 } },
{
$group: {
_id: 1,
items: {
$push: {
name: "$name",
value: "$value"
}
}
}
},
{
$unwind: {
path: "$items",
includeArrayIndex: "index"
}
},
{
$project: {
_id: 0,
name: "$items.name",
value: "$items.value",
index: { $add ["$index", 1] }
}
}
])
Playground: https://mongoplayground.net/p/572ReIpRcl6