MongoDB conditional query with self data - mongodb

Question

Assume that there is 4 users in collections.
> db.users.find().pretty()
{
"_id" : ObjectId("5d369b451b48d91cba76c618"),
"user_id" : 1,
"final_score" : 65,
"max_score" : 15,
"min_score" : 15,
}
{
"_id" : ObjectId("5d369b451b48d91cba76c619"),
"user_id" : 2,
"final_score" : 70,
"max_score" : 15,
"min_score" : 15,
}
{
"_id" : ObjectId("5d369b451b48d91cba76c61a"),
"user_id" : 3,
"final_score" : 60,
"max_score" : 15,
"min_score" : 15,
}
{
"_id" : ObjectId("5d369b451b48d91cba76c61b"),
"user_id" : 4,
"final_score" : 83,
"max_score" : 15,
"min_score" : 15,
}
I want to extract users that meet below conditions.
final_score >= user_id=3's final_score + each document's max_score
final_score <= user_id=3's final_score - each document's min_score
To represent with MySQL, it is very simple.
SELECT * FROM users
WHERE final_score <= 60 + users.max_score AND final_score >= 60 - users.min_score
But I wonder that how can I querying with mongodb?
Thanks.
EDIT
I think it can be execute with this.
So I made query like this.
db.users.find({
'final_score': {
'$lte': '60 + this.max_score',
'$gte': '60 - this.min_score'
}
})
But it return nothing

Answer 1

The difficulty here comes from the fact that you need to run two separate pipelines (one to get the value for user 3 and second one to filter all documents). In Aggregation Framework you can do that using $facet operator which allows you to run multiple pipelines and then keep processing data in subsequent steps. To compare the data you can use $filter and to get original shape as a result you need to transform nested array into separate documents using $unwind and $replaceRoot
db.users.aggregate([
{
$facet: {
user3: [
{ $match: { user_id: 3 } }
],
docs: [
{ $match: {} }
]
}
},
{
$addFields: {
user3: { $arrayElemAt: [ "$user3", 0 ] }
}
},
{
$project: {
docs: {
$filter: {
input: "$docs",
cond: {
$and: [
{ $lte: [ "$$this.final_score", { $add: [ "$user3.final_score", "$$this.max_score" ] } ] },
{ $gte: [ "$$this.final_score", { $subtract: [ "$user3.final_score", "$$this.max_score" ] } ] },
]
}
}
}
}
},
{
$unwind: "$docs"
},
{
$replaceRoot: {
newRoot: "$docs"
}
}
])
Mongo Playground

Answer 2

From your description, I guess you already know the score of user3 is 60.
In this case:
db.collection.aggregate([
{
$addFields: {
match: {
$and: [
{
$gte: [
"$final_score",
{
$subtract: [
60,
"$min_score"
]
}
]
},
{
$lte: [
"$final_score",
{
$add: [
60,
"$max_score"
]
}
]
}
]
}
}
},
{
$match: {
match: true
}
},
{
$project: {
match: 0
}
}
])
mongoplayground