Mongodb changing the unique key - mongodb

Question

I have made the users email the unique key for my entire users database:
var usersSchema = new Schema({
_id: String, // Users Unique Email address
name: String, // Users name
phone: String, // Users phone number
country: String, // Country
type: String, // tenant/agent/manager/admin
username: String, // Username for login
password: String, // Password string
trello: Object, // Trello auth settings
settings: Object, // Settings for manager and other things
createDate: Number, // Date user was created
contactDate: Number, // Date user was last contacted
activityDate: Number // Date of last activity on this user (update/log/etc)
});
So what if the user changes email address?
Is my only way to delete the record and create it again?
Or is there a smarter way?
And the users._id (email) have relations in 16 other tables.
Example the booking table
var bookingSchema = new Schema({
_id: String, // Unique booking ID
user: String, // User ID --> users._id
property: String, // Property ID --> property._id
checkin: Number, // Check in Date
checkout: Number // Check out Date
});
One user can have a LOT of bookings
What I would do is find all records that matches the email and then do a for (i=1 ; i<booking.length ; i++) and then update the email of each record
Is there a smarter way to update all emails that matches using only one mongo call?
(the reason is there are so many relations, so my loop seems a bit like a very primitive way of doing it)

Answer 1

I would say it's much cleaner to create a field for email and create an Unique Index on that.
Unfortunately still the relationship as the ones inside the Relational databases isn't supported! There are plans according to the latest talks to create this feature natively.
The best solution for you would be to think how to use the sub-documents to make things more consistent.