This document provides tips for improving the performance of Ruby on Rails applications. It recommends using the latest Ruby version for performance improvements to memory usage and garbage collection. Specific tips include avoiding temporary variables, chaining methods together, using Enumerable methods like map and reject, using lightweight frameworks like Sinatra, writing database logic in the database, eager loading associations, caching at different levels, and optimizing ActiveRecord queries and routes.

1. Ruby/Rails Performance Tips
Patrick McSweeny

2. About Me
 I really like Ruby
 Organizer of Ann Arbor Ruby Brigade
 Looking for speakers

3. Notes on format
 Briefly touch on many different topics
 Self-study encouraged

4. When to Optimize for Performance
 Application is running slowly
 High resource consumption
 Hosting is getting expensive
 Need to scale

5. When Not to Optimize
 Still a beginner
 Early stages of application development
 Limited number of users for app

6. Background on Ruby
 High level language
 Memory allocations handled by interpreter
 Garbage collector frees up unused memory
 Crucial for limiting memory consumption
 Resource intensive

7. Use the latest version of Ruby possible

8. Use Newer Rubies
 Significant performance improvements with
each version
 Reduced memory consumption
 Garbage collection is more efficient
 Rails 4.2.8 and up is compatible with Ruby 2.4

9. How to Speed Up Ruby

10. Avoid using temporary variables
 Cuts down on memory consumption
 Modify variables in place
 ex: str.downcase! instead of new = str.downcase
 Chain methods together (i.e. functional
programming)
 ex: str.downcase.reverse!

11. Dive into the Enumerable Module
 Use map or map! to run the same method on all
items in collection


12. Dive into the Enumerable Module
 Use .reject/delete_if? to delete items from
collection
 Use .any? instead of .count > 0

13. Use a Lightweight Stack
 Sinatra - Ruby DSL for web framework
 Cuba – Super-lightweight web framework in
pure Ruby
 Mote – Lightweight templating engine

14. Use a Lightweight Stack
 Use only what you need from Rails
 Use ActiveRecord by itself
 Create your own model layer
 Use API Controller for returning JSON
 Create your own controller
 ActionController consists of
 Metal – bare-bones controller class
 A bunch of included modules
 Use Metal Class and only include modules you need

15. Write Less Ruby
 Create gems that use low level language
 C/C++ - not for beginners
 Rust – low-level programming done safely


16. Take the logic
and put it in the database

17. Fast Scalable
Ruby
Databases
✓ ✓

18. Put the logic in the database
 Write custom queries for advanced needs
 Joins
 Sub-queries
 Aggregate (group by) functions
 Math
 Custom database functions
 Database views (named queries)
 Downside is logic is in two different places

19. Alternative Implementations of Ruby
 JRuby – good for heavy loads
 Rubinius – modern approach to implementation

20. Speeding up Rails
 Understand queries executed by ActiveRecord
 ex: Use author.book_ids instead of
author.books.pluck(:id)
 Use sub-queries, other advanced SQL techniques
 Eager load associations
 ex: books = Book.includes(:author).all
 Cuts down on total number of queries executed
 Prevents n + 1 queries


21. Caching
 Page caching – not very flexible
 Action caching – runs filters such as
authentication before loading page
 Fragment Caching

22. Russian Doll Caching
 New in Rails 5
 Cache fragment inside a cache fragment – and
so on
 Child object cache expiration triggers parent
object cache expiration


23. Russian Doll Caching

24. Speeding Up Rails
 Limit use of loops in ActiveRecord
 Pass array of hashes to create method
 Use update_all
 destroy_all/delete_all

25. Speeding Up Rails
 Render a collection of objects in partials all at
once
 ex:

26. Speeding Up Rails
 Clean up routes file
 Information in file is parsed on every request app
receives
 Put most used routes at the top
 Limit auto-generated routes with only and except
params
 ex: resources :books, only: [:index, :show]

27. @PatrickMcSweeny