CODEWITHSUNDEEP
ruby-on-railsrubyoptimizationmongodbmongoid
HappyDeveloper
HappyDeveloper

Reputation: 12805

How to check if a relation exists with MongoID?

Let's say I have 'users' and 'favorites', in a many-to-many relationship.

To add a favorite to a user, I could do something like this:

user.favorites << my_new_favorite unless user.favorites.include?(my_new_favorite)

The problem is that this is not how I would do it in Mongo. This is fetching all the user's favorites (could be thousands), only to check if one of them exists.

Any ideas on how to optimize that line of code to be more performant?

Upvotes: 0

Views: 1301

Answers (3)

HappyDeveloper
HappyDeveloper

Reputation: 12805

I ended up creating my own link() function, based on @rubish answer.

Add this to initializers/mongoid.rb:

module Mongoid
  module Document
    def link(entity)
      add_to_set((entity.class.name.demodulize.downcase!.to_s + '_ids').to_sym, entity.id)
      save!() unless persisted?
      entity.add_to_set((self.class.name.demodulize.downcase!.to_s + '_ids').to_sym, id)
    end
  end
end

And then just link() your many-to-many related entities, eg:

my_new_favorite = Favorite.find_or_initialize_by(:field => 'value')
user.link(my_new_favorite)

Improvements are welcome, I started using ruby last month.

Upvotes: 0

rubish
rubish

Reputation: 10907

You can use mongoid's add_to_set method here.

user.add_to_set(:favorite_ids, my_new_favorite.id)

Upvotes: 2

sevenseacat
sevenseacat

Reputation: 25029

I don't really think the check is necessary at all - Mongoid will automatically handle removing dupes from associations, so just append the favorite as you normally would.

Upvotes: 0

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