pp self ● Masataka Pocke Kuwabara ● Work for Money Forward, Inc. ○ Rails engineer for クラウド会計Plus ○ A maintainer of RBS ● Live in Okayama Read it with the conference app→ (app.kaigionrails.org)
Quiz Rule ● I'll show you two kinds of code ○ using Active Record ○ doing the same things ● You choose the faster code ● Rails 7.1 / mysql2 adapter and MySQL 8.0 / ruby 3.3.0-dev
Explanation: Finding articles of blog_id = 42 ● Lazy evaluation ○ `all` and `where` do not execute SQL, but `to_a` does. ○ It is delayed until when the records are necessary ● Basically, RDBMS should do it if RDBMS can.
Counterexample: Finding articles of blog_id = 42 ● `select` can be faster if it's called several times ○ Because Active Record caches the result to `@records` # A articles = Article.all x = articles.select { _1.is_active } # Article Load (3.1ms) SELECT `articles`.* FROM `articles` y = articles.select { not _1.is_active } # nothing # B x = Article .where(is_active: true) .to_a # Article Load (1.5ms) SELECT `articles`.* FROM `articles` WHERE `articles`.`is_active` = TRUE y = Article .where(is_active: false) .to_a # Article Load (1.9ms) SELECT `articles`.* FROM `articles` WHERE `articles`.`is_active` = FALSE Note: Enumerable#partition is more appropriate.
Pro tips To investigate what SQL is executed ● Use the debug log ● Use `AR::Relation#to_sql` method ○ irb(main):001> Article.all.where(blog_id: 42).to_sql => "SELECT `articles`.* FROM `articles` WHERE `articles`.`blog_id` = 42"
Answer: Checking existence # A Article.all .exists?(blog_id: 42) # Article Exists? (0.9ms) SELECT 1 AS one FROM `articles` WHERE `articles`.`blog_id` = 42 LIMIT 1 # B Article.all .any? { _1.blog_id == 42 } # Article Load (1.7ms) SELECT `articles`.* FROM `articles` 💯 A is faster than B!
Explanation: Checking existence ● Lazy execution, same as Q1. ● Active Record has specific methods such as exists?. ○ Use them instead of Enumerable's method ● Enumerable methods are useful, but it is not optimized for AR. ○ You can easily distinguish by that the method takes a block yielding an AR object ○ But…
You can make any? faster by a hack… ● `any? { … }` needs records to execute the block ● On the other hand, it does not need records if it does not execute the block ● We have `RubyVM::AbstractSyntaxTree.of` to solve this problem!
Money Forward ● Nov. 9: RubyWorld Conference 2023. https://2023.rubyworld-conf.org/ja/ ○ I will talk about RBS. ○ At Matsue (registration closed😢) and Online ● Nov. 16: 各社の技術広報が明かす「RubyKaigiスポンサーの裏話」運営ノウハウ やコミュニティへの想い https://moneyforward.connpass.com/event/298325/ ○ Acha-san will talk about sponsoring RubyKaigi ○ Online event ● We have an X account @moneyforwardDev!
Weekly event to watch RubyKaigi 2023 videos I organize an event to watch RubyKaigi 2023 videos. ● In a zoom meeting. ● At 12:10-12:40 on every Thursday ● Accounced in #rubykaigi channel of ruby-jp slack. ● We'll watch "RubyGems on the watch / Maciej Mensfeld" as the next session in 2nd Nov. ● Feel free to join us!
Answer: Querying exists? in loop # A current_user = User.find(42) can_update = current_user .permissions .exists?(action: :update) # Permission Exists? (0.8ms) SELECT 1 AS one FROM `permissions` WHERE `permissions`.`user_id` = 42 AND `permissions`.`action` = 'update' response = Article.all.map do { title: _1.title, can_update:, } end # B current_user = User.find(42) response = Article.all.map do can_update = current_user .permissions .exists?(action: :update) # Permission Exists? (0.8ms) SELECT 1 AS one FROM `permissions` WHERE `permissions`.`user_id` = 42 AND `permissions`.`action` = 'update' { title: _1.title, can_update:, } end 💯 A is faster than B!
Counterexample: Reduce the difference Active Record query cache can reduce the difference. We can confirm it with `ActiveRecord.cache do -- end` It is enabled by default in controller actions, but disabled in other places, such as job, rails console.
Q4. Querying SELECT in loop # A categories = Category.all.to_a response = Article.all.map do { title: _1.title, categories:, } end # B response = Article.all.map do categories = Category.all.to_a { title: _1.title, categories:, } end
Answer. Querying SELECT in loop # A categories = Category.all.to_a response = Article.all.map do { title: _1.title, categories:, } end # B response = Article.all.map do categories = Category.all.to_a { title: _1.title, categories:, } end 💯 A is faster than B!
AR cache makes it faster, but not faster enough ● AR cache needs to cache boolean value for `exists?` ● But it needs to cache AR model objects for query fetching objects ○ Initialization AR model is heavy
Conclusion ● Imagine and confirm your code executes what SQL ○ Use debug log and `#to_sql` ● You can find the benchmark code from pocke/kaigi-on-rails-2023 GitHub repository. Thanks for your listening!
pocke
niftycorp
masatoshiitoh
cer
techouse
prof18
ivargrimstad
twada
codehex
takefumiyoshii
smashingmag
cherdarchuk
searls
chrislema
morganepeng
thekraken
carmenintech
scottboms
philhawksworth
rmw
kevinliebholz
bryan