Reducing n+1 queries using the Bullet and RSpec gems

by

The most effective way is not at all. There may be some legitimate advantages to reducing n+1 queries in tests, most obviously to speed up overall execution time. It is quite possible, however, that you are either testing too much or making less significant gains than what is possible. I also usually find it unappealing to write additional code to help prop up tests, rather than to contribute to the overall value of the application.

Please allow me to propose an alternate use of your time. Only unit test to the absolute minimum of your comfort level. I personally like to focus on complex methods involving validation related issues and money or other math, you may have different priorities. Drawing the line will free up a whole bunch of time writing the most useless and fragile part of your test suite that will occupy the majority of your maintenance budget.

Now, what to do will all of your extra time? Don’t worry, we’ll find something for you to do… You can start by writing some acceptance tests, particularly for the areas that use the objects that you just dropped a whole bunch of unit tests for. Now your n+1 warnings are actually coming from the same spot they will when the user hits the page. Now you can go on to remove all of the n+1 queries.

But wait! Don’t do that either. Instead, spend a good deal less time setting up your relationships to use the touch option. Then, when a child object gets updated, the parent will be updated, too. What the hell does this have to do with n+1 queries, you might be wondering. It seems like we’re just adding queries…

That’s where the Russian doll caching comes in. Adding this, and properly testing it, will consume the freed up unit testing and n+1 elimination time (and then some, if you’re not careful). The nice thing is that it is way more “real world”, much more resilient to insignificant or irrelevant implementation changes in your models and whatnot, and a huge performance boost to your application well beyond what eliminating every n+1 query by eagerly loading everything up front might have provided. You will want to move as much as possible into nested caching and load everything as lazily as humanly possible, to take full advantage of this method.

Long live n+1!

More Related Contents:

  1. Suppress Ruby warnings when running specs
  2. How to check a checkbox in capybara?
  3. undefined method `visit’ when using RSpec and Capybara in rails
  4. Controller spec unknown keyword: id
  5. Why not use shared ActiveRecord connections for Rspec + Selenium?
  6. Why is Rspec saying “Failure/Error: Unable to find matching line from backtrace”?
  7. Why does adding “sleep 1” in an after hook cause this Rspec/Capybara test to pass?
  8. Begin, Rescue and Ensure in Ruby?
  9. How to “pretty” format JSON output in Ruby on Rails
  10. Rails :dependent => :destroy VS :dependent => :delete_all
  11. difference between collection route and member route in ruby on rails?
  12. Using Rails serialize to save hash to database
  13. Rails has_many :through Find by Extra Attributes in Join Model
  14. Rails keeps telling me that it’s not currently installed
  15. Nokogiri installation fails -libxml2 is missing
  16. Get person’s age in Ruby
  17. Rails formatting date
  18. accepts_nested_attributes_for with belongs_to polymorphic
  19. How do you configure WEBrick to use SSL in Rails?
  20. @ variables in Ruby on Rails
  21. gem install permission problem
  22. Can I write PostgreSQL functions on Ruby on Rails?
  23. Double colons before class names in Ruby?
  24. url encode equivalent in ruby on rails
  25. Storing Objects in a Session in Rails
  26. What is the difference between Gemfile and Gemfile.lock in Ruby on Rails
  27. Parametrized get request in Ruby?
  28. Why is respond_with being removed from rails 4.2 into it’s own gem?
  29. Customizing Devise error messages in Rails 3?
  30. How do I use CSS with a ruby on rails application?

Leave a Comment