Push or add to collection in mongoose - arrays

Question

I have a lot of objects I'm saving to Mongoose. They are deep objects.
var obj1 = {
first_name : 'adam',
last_name: 'smith',
car : [{
make: 'honda',
model: 'civic',
colors: [{
name: 'red',
code: 'ff0000'
}]
}]
}
Going in to a matching model like so:
var Owner = new Schema({
first_name: String,
last_name: String,
cars:[{
make: String,
model: String
colors: [{
name: String,
code: String
}]
}]
});
Which is all fine and dandy, unless adam has a second record:
var obj2 = {
first_name : 'adam',
last_name: 'smith',
car : [{
make: 'ford',
model: 'focus',
colors: [{
name: 'blue',
code: '0000ff'
}]
}]
}
var obj3 = {
first_name : 'adam',
last_name: 'smith',
car : [{
make: 'honda',
model: 'civic',
colors: [{
name: 'blue',
code: '0000ff'
}]
}]
}
Each overwrites the previous one completely when I do something like:
Owner.findOneAndUpdate({first_name:"adam", last_name: "smith"}, obj2, {upsert: true});
How do I get mongoose to create a new record when there isn't one, but append to the car array when there is? And if the car already exists, append to the colors array?
To make things a little more fun, the structure of the data is not consistent in my case. It is for a given collection, but each of my collections are being set up dynamically, so the model may be many layers deep and have any given keys.

Answer 1

This approaches allows you to push a new element onto an array field
db.findOneAndUpdate(
{first_name:"adam", last_name: "smith"},
{ $push: { cars : {
make: 'ford',
model: 'focus'
}
}
},
{ safe: true,
upsert: false,
new : true
}
);
I feel your pain regarding trying to guess syntax for arbitrarily complex insert/update/deletes ... the world of mongo/mongoose is screaming for a tool to read Schemas/data and let you interactively describe your particulars to synthesize code snippets like above