elemMatch combined with other query fields in Mongoose

Question

Sample data: ``` [{ "_id": "529532bee0ea703842000003", "patientId": "123", "name": { "firstName": "John", "family": "Smith" }, "diet": [{ "_id": "1", "mealtType": "Break Fast", "timeofMeal": "2013-11-12T03:05:06.000Z", "status": "I", "calorie": { "value": 500, "unit": "cals" } }, { "_id": "1", "mealtType": "Break Fast", "timeofMeal": "2013-11-12T03:05:06.000Z", "status": "A", "calorie": { "value": 550, "unit": "cals" } }] }] ``` I wanted to fetch only active (status 'A') embedded document (diet document) for a given patientId ('123') using mongoose in node. Here is my mongoose query: ``` query.where('patientId', 123) .where('diet').elemMatch(function(elem) { elem.where('_id', 1) elem.where('status', 'A') }) ``` Mongoose generated below query, which is brining all elements from embedded array diet for patient. ``` Mongoose: patients.find({ diet: { '$elemMatch': { _id: '1', status: 'A' } }, patientId: '123' }) ``` The above query fetches all sub documents irrespective of status at Mongo…

Accepted Answer

In your query that works, the `$elemMatch` object is not another query condition, but is the output field selection (i.e. projection) parameter to `find`.

To do the same in Mongoose, you'd do something like:

```
PatientsModel.find({patientId: '123'}, {diet: {$elemMatch: {'status': 'A'}}}, cb)
```

OR

```
PatientsModel
    .where('patientId', '123')
    .select({diet: {$elemMatch: {'status': 'A'}})
    .exec(cb);
```

elemMatch combined with other query fields in Mongoose

Solution

Problem