Hide embedded document in mongoose/node REST server - node.js

Question

I'm trying to hide certain fields on my GET output for my REST server. I have 2 schema's, both have a field to embed related data from eachother into the GET, so getting /people would return a list of locations they work at and getting a list of locations returns who works there. Doing that, however, will add a person.locations.employees field and will then list out the employees again, which obviously I don't want. So how do I remove that field from the output before displaying it? Thanks all, let me know if you need any more information.
/********************
/ GET :endpoint
********************/
app.get('/:endpoint', function (req, res) {
var endpoint = req.params.endpoint;
// Select model based on endpoint, otherwise throw err
if( endpoint == 'people' ){
model = PeopleModel.find().populate('locations');
} else if( endpoint == 'locations' ){
model = LocationsModel.find().populate('employees');
} else {
return res.send(404, { erorr: "That resource doesn't exist" });
}
// Display the results
return model.exec(function (err, obj) {
if (!err) {
return res.send(obj);
} else {
return res.send(err);
}
});
});
Here is my GET logic. So I've been trying to use the query functions in mongoose after the populate function to try and filter out those references. Here are my two schema's.
peopleSchema.js
return new Schema({
first_name: String,
last_name: String,
address: {},
image: String,
job_title: String,
created_at: { type: Date, default: Date.now },
active_until: { type: Date, default: null },
hourly_wage: Number,
locations: [{ type: Schema.ObjectId, ref: 'Locations' }],
employee_number: Number
}, { collection: 'people' });
locationsSchema.js
return new Schema({
title: String,
address: {},
current_manager: String, // Inherit person details
alternate_contact: String, // Inherit person details
hours: {},
employees: [{ type: Schema.ObjectId, ref: 'People' }], // mixin employees that work at this location
created_at: { type: Date, default: Date.now },
active_until: { type: Date, default: null }
}, { collection: 'locations' });

Answer 1

You should specify the fields you want to fetch by using the select() method. You can do so by doing something like:
if( endpoint == 'people' ){
model = PeopleModel.find().select('locations').populate('locations');
} else if( endpoint == 'locations' ){
model = LocationsModel.find().select('employees').populate('employees');
} // ...
You can select more fields by separating them with spaces, for example:
PeopleModel.find().select('first_name last_name locations') ...

Answer 2

Select is the right answer but it also may help to specify it in your schema so that you maintain consistency in your API and I've found it helps me to not remember to do it everywhere I perform a query on the object.
You can set certain fields in your schema to never return by using the select: true|false attribute on the schema field.
More details can be found here: http://mongoosejs.com/docs/api.html#schematype_SchemaType-select

Answer 3

SOLUTION!
Because this was so hard for me to find i'm going to leave this here for anybody else. In order to "deselect" a populated item, just prefix the field with "-" in your select. Example:
PeopleModel.find().populate({path: 'locations', select: '-employees'});
And now locations.employee's will be hidden.

Answer 4

If you remember from you SQL days, SELECT does a restriction on the table(s) being queried. Restrict is one of the primitive operations from the relational model and continues to be a useful feature as the relational model has evolved. blah blah blah.
In mongoose, the Query.select() method allows you to perform this operation with some extra features. Particularly, not only can you specify what attributes (columns) to return, but you can also specify what attributes you want to exclude.
So here's the example:
function getPeople(req,res, next) {
var query = PeopleModel.find().populate({path: 'locations', select: '-employees'});
query.exec(function(err, people) {
// error handling stuff
// process and return response stuff
});
}
function getLocations(req,res, next) {
var query = LocationModel.find().populate({path: 'employees', select: '-locations'});
query.exec(function(err, people) {
// error handling stuff
// processing and returning response stuff
});
}
app.get('people', getPeople);
app.get('locations', getLocations);
Directly from the Mongoose Docs:
Go to http://mongoosejs.com/docs/populate.html and search for "Query conditions and other options"
Query conditions and other options
What if we wanted to populate our fans array based on their age,
select just their names, and return at most, any 5 of them?
Story
.find(...)
.populate({
path: 'fans',
match: { age: { $gte: 21 }},
select: 'name -_id',
options: { limit: 5 }
})
.exec()
I just wanted to remark, for the simplicity of the endpoint you may be able to get away with this way to define the endpoints. However, in general this kind of dispacher pattern is not necessary and may pose problems later in development when developing with Express.