Need desired outcome in populate block with customized result in mongodb - mongodb

Question

I have four collections person , other_details, occupation_details, bank_details as stated below
person =>[
{
id : 1,
name : 'john',
other_details : 1023
},
{
id : 2,
name : 'mark',
other_details : 99
}
]
other_details => [
{
id: 1023,
married: false,
occupation_details: 144,
bank_details : 10
},
{
id: 99,
married: true,
occupation_details: 45,
bank_details : 11
}
]
occupation_details => [
{
id: 144,
comp_name : 'oscorp inc.'
},
{
id: 45,
comp_name : 'tesla inc.'
}
]
bank_details => [
{
id: 10,
bank : 'Bank of canada'
},
{
id: 11,
bank : 'Peoples bank of canada'
}
]
I am using mongoose library with nodejs
// id = 1
person.findById(id).populate({
path: 'other_details',
populate: [
{
path: 'occupation_details'
},
{
path: 'bank_details'
}
]
})
So the result for the above query comes like below
=>
{
id : 1,
name : 'john',
other_details : {
id: 1023,
married: false,
occupation_details: {
id: 144,
comp_name : 'oscorp inc.'
},
bank_details : {
id: 10,
bank : 'Bank of canada'
}
}
}
But for some reasons I want the result like below
{
id : 1,
name : 'john',
other_details : {
id: 1023,
married: false,
occupation_details: {
id: 144,
comp_name : 'oscorp inc.'
},
bank_details : 10,
custom_bank_details : {
id: 10,
bank : 'Bank of canada'
}
}
}
The change I need is the following, The bank_details object should exist with id and the populated bank_details data from other collection should come in other object name as custom_bank_details
bank_details : 10,
custom_bank_details : {
id: 10,
bank : 'Bank of canada'
}

Answer 1

Update:
You could use virtual to populate bank details into a new field. Something like
OtherDetailsSchema.virtual('custom_bank_details', {
ref: 'BankDetails',
localField: 'bank_details',
foreignField: '_id',
justOne: true
});
Person.findById(id).populate({
path: 'other_details',
populate: [
{path: 'occupation_details'},
{path: 'custom_bank_details'}
]})
Original
I'm not a mongoose user so I'm not sure if it is possible to populate to new field name. If feasible you could quite easily achieve using aggregate with lookup.
Something like
person.aggregate([
{"$lookup":{
"from":"other_details",
"let":{"other_details":"$other_details"},
"pipeline":[
{"$match":{"$expr":{"$eq":["$id","$$other_details"]}}},
{"$lookup":{
"from":"occupation_details",
"localField":"occupation_details",
"foreignField":"id",
"as":"occupation_details"
}},
{"$unwind":"$occupation_details"},
{"$lookup":{
"from":"bank_details",
"localField":"bank_details",
"foreignField":"id",
"as":"custom_bank_details"
}},
{"$unwind":"$custom_bank_details"},
],
"as":"other_details"
}},
{"$unwind":"$other_details"}
])
Working example https://mongoplayground.net/p/5Kee0tBQmTd