SmartPreloader

Smart preloader allows to:

• Preload polymorphic associations
• Filter records for preloading
• Preload composite key associations

Installation

Add this line to your application's Gemfile:

gem 'smart_preloader'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install smart_preloader

Usage

Preload polymorphic associations

class Comment < ApplicationRecord
  belongs_to :owner, polymorphic: true # User or Post
end

To preload use the same syntax as for Rails eager load with one extra layer for polymorphic association Use class constants to specify corresponding preloads

comments = Comment.all
ActiveRecord::SmartPreloader.(comments, owner: [
  User => :account,
  Post => :votes
])

Class name in preload tree considered as a filter for a records

Filter records for preloading

It allows filter records at ruby level for further preloading

comments = Comment.all
ActiveRecord::SmartPreloader.(comments, ->(comment) { comment.rated? } => :author)

The code filters rated? comments and preloads Comment#author association

Preload composite key associations

Models could be referenced not by single id but by composite/multi key, like [:category_id, :author_id]

class AuthorRating < ApplicationRecord
  belongs_to :author
  belongs_to :category
end
class Post < ApplicationRecord
  belongs_to :category
  belongs_to :author
  has_one :author_rating,
          ->(post) { where(category_id: post.category_id) },
          class_name: 'AuthorRating', foreign_key: :author_id, primary_key: :author_id
end

To preload post's author rating in the category:

ActiveRecord::SmartPreloader.(posts, ActiveRecord::CompositeKey.new(:author_rating, [:author_id, :category_id]))

and it could be put in tree as usual:

ActiveRecord::SmartPreloader.(comments, post: [
  ActiveRecord::CompositeKey.new(:author_rating, [:author_id, :category_id]) => :voters
])

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/2rba/smart_preloader.

License

The gem is available as open source under the terms of the MIT License.