Question

Let’s say I have the following models:

Class Wishlist
    belongs_to :user # User class is irrelevant here
    has_many :inclusions
    has_many :products, :through => :inclusions
  end

  Class Product
    has_many :inclusions
    has_many :wishlists, :through => :inclusions
  end

  Class Inclusion
    belongs_to :product
    belongs_to :wishlist
  end

inclusions/index.html.erb

  <%= render @inclusions %>

inclusions/_inclusion.html.erb

  <%= "#{ inclusion.quantity } #{ inclusion.product.name } #{ inclusion.wishlist.user.name }"%>

This example is trivial, but the point is: the amount of database queries is overwhelming. For every instance of _inclusion.html.erb, at least three new queries seem to be created.
Is there a way to prefetch this information beforehand, maybe through a JOIN command?

Answer 1

Maybe this can help:

 @inclusions = Inclusions.includes(:product, { :wishlist => :user })

Read about eager loading.