How to retrieve parent document based on subdocument values in Mongoose?

Question

I have the following schema's:

var Child = new mongoose.Schema({
    'field': String,
    'value': String
  });

var Parent = new mongoose.Schema({
    'name': String,
    'children': [ Child ]
  });

I want to return the Parent for which one of the Child's corresponds to the following JSON object:

{ 'field': 'Family Name', 'value': 'Smith' }

I have tried this:

Parent.findOne({ 'children': { 'field': 'Family Name', 'value': 'Smith' } }, fn ...)

but it keeps on retrieving null.

EDIT:

Testing through the Mongo shell extension, I found out that the Child sub-documents have their own _id's. If I add that _id to the query, it fetches the parent document. Now, I don't know in advance what that child id will be. So: how can I remove it from the sub-document query? (In other words, the above query literally looks for a JSON object with only two properties, while the sub-documents have three)

My environment is: Node.js, Mongoose, MongoDB

Answer 1

It seems the $elemMatch is the query operator to solve this problem. The actual query should be written as follows:

Parent.findOne({ 'children': { $elemMatch: { 'field': 'Family Name', 'value': 'Smith' } } }, fn ...)

Answer 2

Is there a reason you use field, value structure on the child documents? It would be easier to simply use the key as the field, like {"FamilyName": "Smith"}. This would allow something like:

Parent.findOne({'children.FamilyName': 'Smith'}, function(err, doc){...});