CODEWITHSUNDEEP
mongodb
Faysal Ahmed
Faysal Ahmed

Reputation: 1542

merge mongodb aggregate result

I have one collection say user. Structure of each document is something like this

_id:String
status:Int32
account:{
    firstName:
    lastName:
    .. some other nested property
}
..some more property

My end goal is to generate a new nested field fullName in accountfield which is a concatenation of two name fields. I can run aggregate query like this

db.user.aggregate(
[
  { $project: { 'account.name': { $concat: [ "$account.firstName", "  ", "$account.lastName" ] } } }
])

if I write $out along with db name, but my existing data get replaced. How do I actually merge so that my final structure remains as

_id:String
status:Int32
account:{
    firstName:String
    lastName:String
    fullName:String
    .. some other nested property
}
..some more property

Upvotes: 1

Views: 560

Answers (1)

chridam
chridam

Reputation: 103305

In your $project pipeline, you need to include the other fields using the dot notation on the embedded fields as follows:

db.user.aggregate([
    { 
        "$project": { 
            "status": 1,
            "field1": 1, // the other properties
            "field2": 1,
            "account.firstName": 1,
            "account.lastName": 1,
            "account.name": {"$concat":["$account.firstName", "  ", "$account.lastName"]}  
        } 
    },
    { "$out": "tempcollection" }
])

Upvotes: 1

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