How to get child document from a collection in mondodb?

Question

I have created a collection which has sub collection data. I want to filter from sub collection with a key.

Here is my document:

{
    "_id" : ObjectId("5758098356e3930537af15dd"),
    "manpower_data" : [ 
        {
            "_id" : ObjectId("5758098356e3930537af15de"),
            "created" : ISODate("2016-06-08T12:03:15.387Z"),            
            "designation" : "Visiting Evaluator",            
            "evaluatorContactNumber" : "987654321",            
            "evaluatorName" : "Dumy User1",
            "dealerCodeFor" : "ZSAE876",
            "region" : "Gurgaon"
        }, 
        {
            "_id" : ObjectId("5758098356e3930537af15de"),
            "created" : ISODate("2016-06-08T12:03:15.387Z"),            
            "designation" : "Resident Evaluator",            
            "evaluatorContactNumber" : "987654321",            
            "evaluatorName" : "Dumy User2",
            "dealerCodeFor" : "ZSAE877",
            "region" : "Delhi"
        }
    ]
}

When I run this query

db.mycollection.find({"manpower_data.dealerCodeFor":"ZSAE876"});

It returns me all two sub document but I want to get only those manpower data which has matching dealerCodeFor.

score 3 · Accepted Answer · answered Jun 20 '16 at 12:17

3

To filter array elements, query projection phase with $elemMatch need to be executed. Please see example below:

db.collection.find({
    "manpower_data.dealerCodeFor" : "ZSAE876"
}, {
    manpower_data : {
        $elemMatch : {
            dealerCodeFor : "ZSAE876"
        }
    }
})

answered Jun 20 '16 at 12:17

profesor79

9,213
3
31
52

It works. Thank you :) – Anuranjan Pandey Jun 20 '16 at 12:40
1

NOTE:- This will only return first matching object from the array. If there are multiple you won't get them all. – Shrabanee Jun 20 '16 at 13:10

Shrabanee · Answer 2 · 2016-06-20T13:43:43.697

2

You can use $filter of aggregate-mongodb to achieve this.

Try the following:-

db.collection.aggregate([
{ 
    "$match": {"manpower_data.dealerCodeFor":"ZSAE876"}
},
{
    "$project": {
        "manpower_data": {
            "$filter": {
                "input": "$manpower_data",
                "as": "o",
                "cond": {  
                    "$eq": ["$$o.dealerCodeFor", "ZSAE876"]
                }
            }
        }
    }
}])

By running the above query, manpower_data will return only the objects, which matches your condition.

EDIT:-

For version less than 2.6.x, try following query:-

db.collection.aggregate([
{ 
    "$match": {"manpower_data.dealerCodeFor":"ZSAE876"}
},  
{ "$unwind": "$manpower_data" },
{ 
    "$match": {"manpower_data.dealerCodeFor":"ZSAE876"}
},
{
    "$group": {
        "$_id": "$_id",
        "manpower_data": { "$push": "$manpower_data" }
    }
}])

edited Jun 20 '16 at 13:43

answered Jun 20 '16 at 12:22

Shrabanee

2,706
1
18
30

@Shrebanee I run the above query but gave me error `uncaught exception: aggregate failed: { "errmsg" : "exception: invalid operator '$filter'", "code" : 15999, "ok" : 0 }` – Anuranjan Pandey Jun 20 '16 at 12:35
why aggregate here? is a shotgun to kill a little fly :-), – profesor79 Jun 20 '16 at 12:43
@profesor79 I thought, if there are multiple objects inside the array, matching the query, projecting all those objects can be done through aggregate. – Shrabanee Jun 20 '16 at 13:11
@AnuranjanPandey forgot to mention, this can be used only with mongodb version 3.2.x. What is the version you are using? – Shrabanee Jun 20 '16 at 13:12
MongoDB shell version: 2.4.9 – Anuranjan Pandey Jun 20 '16 at 13:38
1

@AnuranjanPandey Edited my answer with the query that can help you. – Shrabanee Jun 20 '16 at 13:44

How to get child document from a collection in mondodb?

2 Answers2