Find object id in object ids array returns empty array using Mongoose

Question

I have two Mongoose schemas:

var EmployeeSchema = new Schema({
    name: String,
    servicesProvided: [{
        type: mongoose.Schema.Types.ObjectId,
        ref: 'Service'
    }]
});

var ServiceSchema = new Schema({
    name: String
});

I'm trying to find employees who provide a specified service with the service ID I send into the http request. This is my code:

Employee
  .find({
    servicesProvided: req.params.service_id
  })
  .exec(function(err, employees) {
    if (err) {
      console.log(err);
      res.send(err);
    } else {
      res.json(employees);
    }
});

The problem is that this code returns an empty array and I don't know why. I've tried a lot of things like casting the service id to mongoose.Schema.Types.ObjectId but it doesn't work.

Any idea? I'm using Mongoose 3.8.39. Thanks!

alexmac · Accepted Answer · 2016-04-07 16:36:44Z

3

In your EmployeeSchema, servicesProvided is an array, to filter employees by that field you should use $in operator:

var services = [req.params.service_id];
Employee.find({
  servicesProvided: {
    $in: services
  }
}, ...

answered Apr 7, 2016 at 16:36

alexmac

19.7k7 gold badges64 silver badges74 bronze badges

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

8 Comments

Andrey Popov Over a year ago

This searches for documents inside provided array which is bad overhead.

alexmac Over a year ago

@AndreyPopov With index or small lists It can be fairly efficient.

Andrey Popov Over a year ago

I agree, but still it's not needed. Today it's a small list, tomorrow it's a huge bottleneck :) If you can make it easier from the beginning - why not?

gonver Over a year ago

Thank you for your answer, it works properly but I'll choose the other answer if is more efficient.

alexmac Over a year ago

Np, I agree that solution suggested by @AndreyPopov is more preferable in that concrete scenario.

|

Andrey Popov · Accepted Answer · 2016-04-07 16:47:13Z

2

I think you need $elemMatch! From docs:

{ _id: 1, results: [ { product: "abc", score: 10 }, { product: "xyz", score: 5 } ] },
{ _id: 2, results: [ { product: "abc", score: 8 }, { product: "xyz", score: 7 } ] },
{ _id: 3, results: [ { product: "abc", score: 7 }, { product: "xyz", score: 8 } ] }

Search like:

db.survey.find({ results: { $elemMatch: { product: "xyz", score: { $gte: 8 } } } })

Results in:

{ "_id" : 3, "results" : [ { "product" : "abc", "score" : 7 }, { "product" : "xyz", "score" : 8 } ] }

But since you're doing a single query condition (look at the docs again) you can replace

db.survey.find(
   { results: { $elemMatch: { product: "xyz" } } }
)

with

db.survey.find(
   { "results.product": "xyz" }
)

So in your case it should be something like:

find({
    'servicesProvided': ObjectId(req.params.service_id)
})

answered Apr 7, 2016 at 16:47

Andrey Popov

7,5404 gold badges45 silver badges60 bronze badges

4 Comments

gonver Over a year ago

Sorry, It does not work either answers. Your first one returns an empty array and the second one returns a reference error : ObjectId is not defined. If I use mongoose.Schema.Types.Object(req.params.service_id) doesn't work either.

Andrey Popov Over a year ago

I don't know what's my 'first' and 'second' one, and why it's not working, as this should be the proper way (even tested it locally). Not sure what's going on at your place. You can accept the other answer if it suits your needs, but keep in mind to test it out what's going on and why this is not working. Again, check the online manual just to be sure ;)

Andrey Popov Over a year ago

stackoverflow.com/questions/12451358/…

gonver Over a year ago

Your first answer was: 'servicesProvided': req.params.service_id and your second one: 'servicesProvided._id': ObjectId(req.params.service_id). I'm sure that is the proper way but for some reason it doesn't work. I've read about this problem in many internet forums, maybe is a bug of a Mongoose version.

Collectives™ on Stack Overflow

Find object id in object ids array returns empty array using Mongoose

2 Answers 2

8 Comments

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

8 Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related