smart_preloads

smart_preloads

Avoid N + 1 queries without having to worry about it at all! It is also useful when you do not have control over which associations are going to be used by the view, like when you provide users customizable views with Liquid.

Installation

You can use gem install smart_preloads to install it manually or use Bundler:

gem 'smart_preloads'

Usage

You have to call smart_preloads at the end of your association. This will generate a smart list of items that will load associations if and when they are needed.

@authors = Author.all.smart_preloads

@authors.each do |author|
  puts author.name
end
#=> SELECT "authors".* FROM "authors"

@authors.each do |author|
  author.books.each do |book|
    puts "#{author.name} authored #{book.name}"
  end
end
#=> SELECT "books".* FROM "books" WHERE "books"."author_id" IN (1, 2)

Note that when books is called for the first record, that association will be loaded for all records at once. This works for nested associations too:

@authors.each do |author|
  author.books.each do |book|
    puts "#{author.name} authored #{book.name} (#{book.category.name})"
  end
end
#=> SELECT "categories".* FROM "categories" WHERE "categories"."id" IN (1, 2)

How it Works

In order for it to work, smart_preloads has a custom list class (SmartPreloads::List) and a custom item class for each item in a list (SmartPreloads::Item).

The List class allows detecting when the collection is really used (iterated) so only then the associations will be detected and mokey patched in place. This is needed so whenever a call to an association is made it will be loaded, even from calls from within the object itself.

The Item class monkey patches all association methods in the objects loaded to intercept the calls. The monkey patch is in place, not global. Only the objects in the smart_preloads collection will be monkey patched.

Note that when you call Author.all.smart_preloads.first you will not have an instance of Author. Instead, you will have an instance of SmartPreloads::Item that delegates calls to the original Author object.

Contributing

• Fork the project.
• Start a feature/bugfix branch.
• Commit and push until you are happy with your contribution.
• Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
• Create a pull request.

Copyright

Copyright (c) 2017 Diego Aguir Selzlein. See LICENSE.txt for further details.