CODEWITHSUNDEEP
mongodbmongodb-queryaggregate
Weq Iou
Weq Iou

Reputation: 243

mongodb aggregate always return null in array of the collection object

I have a person like this, The person has many companies, [ ONE TO MANY ]

{
        "_id" : ObjectId("5eef12533167638883fba5ad"),
        "companies" : [  
                         ObjectId("00000000000000000011111") , 
                         ObjectId("0000000000000000022222") 
                      ],
        "email" : "[email protected]",
        "phoneNumber" : "+1689999999999",
        "createdAt" : ISODate("2020-06-21T07:54:56.529Z"),
        "updatedAt" : ISODate("2020-06-21T07:54:56.529Z")
}

I want to aggregate companies into the company data I am trying like this

db.people.aggregate(
  { "$lookup": {
    "from": "companies",
    "localField": "companies",
    "foreignField": "_id",
    "as": "companies"
  }},
)

but the result is the same as query db.people.find() how to correct way to query that she in that array show the companies data ,

what I expected is :

{
        "_id" : ObjectId("5eef12533167638883fba5ad"),
        "companies" : [  
                         {
                           "_id": ObjectId("00000000000000000011111"),
                            "name": "Company one"
                          },
                           ..... so on
                      ],
        "email" : "[email protected]",
        "phoneNumber" : "+1689999999999",
        "createdAt" : ISODate("2020-06-21T07:54:56.529Z"),
        "updatedAt" : ISODate("2020-06-21T07:54:56.529Z")
}

Upvotes: 0

Views: 187

Answers (1)

Shihab
Shihab

Reputation: 2679

IMPORTANT: Starting MongoDB 3.4, if the localField is an array, you can match the array elements against a scalar foreignField without needing an $unwind stage.

I believe your aggregate call is not right. .aggregate() receives an array.

db.people.aggregate([
  { 
   $lookup: {
    from: "companies",
    localField: "companies",
    foreignField: "_id",
    as: "companies"
   }
  }
])

Make sure the from, localField and foreignField are correct.

Upvotes: 1

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