How to query an object in an array embedded in mongodb?

Question

I am currently working on an application that takes control of Projects, which have Meetings and that these meetings have Participants.

I want to consult a Participant by his nomina field.

Structure for a project document object:

 {
       "id":"5c1b0616a0441f27f022bfdc",
       "name":"Project Test",
       "area":"Area",
       "date":"2019-01-01",
       "meetings":[
          {
             "id":"5c1b073d445707834699ce97",
             "objetive":"Objetive",
             "fecha":"2019-01-01",
             "participants":[
                {
                   "nomina":1,
                   "name":"Person 1",
                   "role":"Rol1",
                   "area":"area1",
                   "signature":null
                },
                {
                   "nomina":2,
                   "name":"Person 2",
                   "role":"rol 2",
                   "area":"área 2",
                   "signature":null
                }
             ]
          }
       ]
    }

Expected behavior

I want to consult a Participant by nomina field knowing the id of the Project and also knowing the id of the Meeting.

Expected output

Having:

id Project = 5c1b0616a0441f27f022bfdc
id Meeting = 5c1b073d445707834699ce97
nomina Participant = 1

It's expected that the query will return me:

{    
"nomina":1,             
"name":"Person 1",
"role":"Rol1",
"area":"area1",
"signature":null
}

Babak · Accepted Answer · 2019-01-02 15:05:20Z

1

For not so huge number of meetings in every document if you want to get the exact document stated, you can do this pipeline, it is straight forward:

db.collection.aggregate(
    [
       {
            $match: {
              id:"5c1b0616a0441f27f022bfdc"             
            }
        },          {
            $unwind: {
                path : "$meetings"
            }
        },
        {
            $unwind: {
                path : "$meetings.participants"
            }
        },
        {
            $match: {
              "meetings.id":"5c1b073d445707834699ce97",
              "meetings.participants.nomina":1

            }
        },
        {
            $replaceRoot: {
                newRoot: "$meetings.participants"
            }
        }
    ]);

If you would have over thousands of elements in meetings then I'd suggest adding another match to meetings or grouping meetings and project IDs. But if you just want to get the document containing what you want it is just a simple find query:

db.collection.find({id:"5c1b0616a0441f27f022bfdc","meetings.id":"5c1b073d445707834699ce97","meetings.participants.nomina":1 });

edited Jan 2, 2019 at 15:05

answered Jan 2, 2019 at 14:59

Babak

6136 silver badges15 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Gibrán Over a year ago

Hi, thanks.

db.collection.find({id:"5c1b0616a0441f27f022bfdc","meetings.id":"5c1b073d445707834699ce97","meetings.participants.nomina":1 });

this will always return me the entire document? I ran the example here

Babak Over a year ago

Yes, that would bring the whole document containing the conditions you want, but if you have at most a couple of thousand elements in "meetings" array, you can easily go with aggregation pipeline.

Gibrán Over a year ago

Sorry, and now that I know the Participant with nomina= 1, how could modify his signature field?

Babak Over a year ago

You mean you want to update that document ? nodechef.com/docs/cloud-search/… Something like this should work: db.collection.update({id:"5c1b0616a0441f27f022bfdc","meetings.id":"5c1b073d445707834699ce97","meetings.participants.nomina":1 },{$set:{"meetings.participants.$$.signature":1122}}, false, true )

Babak Over a year ago

Oh yup, sorry about that, what is the tool or language that your are working with mongo on ?

|

Collectives™ on Stack Overflow

How to query an object in an array embedded in mongodb?

1 Answer 1

8 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

8 Comments

Your Answer

Sign up or log in

Post as a guest

Related