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Aaron Patterson 8af85e161d
Reduce the number of times we look up the ScopeRegistry
I noticed in profiles of simple queries (like `Post.where(id: 1).first`)
we're spending lots of time looking up the current thread.  I couldn't
find any way to speed this up in Ruby, so I thought maybe we could call
`Thread.current` fewer times per query.

This patch should eliminate 4 calls to `Thread.current` per query.

For this benchmark:

```ruby
  StackProf.run(mode: :wall, out: 'out.dump') do
    8000.times { Post.where(id: id).first }
  end
```

`Thread.current` goes from 7% to 4.7% of time:

```
==================================
  Mode: wall(1000)
  Samples: 1633 (0.00% miss rate)
  GC: 51 (3.12%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       140   (8.6%)         140   (8.6%)     String#sub!
       114   (7.0%)         114   (7.0%)     Thread.current
```

```
==================================
  Mode: wall(1000)
  Samples: 1719 (0.00% miss rate)
  GC: 51 (2.97%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       134   (7.8%)         134   (7.8%)     String#sub!
        99   (5.8%)          99   (5.8%)     Module#===
        81   (4.7%)          81   (4.7%)     Thread.current
```

This isn't huge, but I think we need to find more sources of
Thread.current.  It's surprising to me that we spend so much time
looking up the current thread when doing a query that is so "easy"
2021-04-02 12:31:05 -07:00
.github Rename master to main in all code references 2021-01-19 20:46:33 +00:00
actioncable Refactor to use model instead of record as argument in Action Cable 2021-02-25 11:21:19 -03:00
actionmailbox 'lookup' -> 'look up' in dummy webpacker.ymls 2021-03-21 12:36:56 +00:00
actionmailer Fix ActionMailer's deliver later default queue 2021-03-05 10:16:55 +01:00
actionpack Merge pull request #40789 from csutter/deprecate-remote-ip-single-value 2021-03-24 02:27:57 -04:00
actiontext 'lookup' -> 'look up' in dummy webpacker.ymls 2021-03-21 12:36:56 +00:00
actionview Revert "Passing in a Hash instance as non-kwargs parameters has to be curly braced now" 2021-03-22 11:21:33 +09:00
activejob Use ... argument forwarding instead of ruby2_keywords when possible 2021-03-19 16:53:06 +01:00
activemodel Remove useless include_private parameter in define_proxy_call 2021-03-20 14:27:53 -04:00
activerecord Reduce the number of times we look up the ScopeRegistry 2021-04-02 12:31:05 -07:00
activestorage 'lookup' -> 'look up' in dummy webpacker.ymls 2021-03-21 12:36:56 +00:00
activesupport Merge pull request #41684 from ricardotk002/disable-parallel-testing 2021-03-23 09:06:57 -04:00
ci Remove .travis.yml and ci/travis.rb 2020-01-02 09:27:53 +09:00
guides Document Destroy Async (#41680) 2021-03-24 00:54:50 -04:00
railties Merge pull request #40789 from csutter/deprecate-remote-ip-single-value 2021-03-24 02:27:57 -04:00
tasks Fix a rubocop offence for Lint/ErbNewArguments 2021-02-05 12:39:58 +09:00
tools Fix bin/test 2020-10-30 21:33:19 +00:00
.gitattributes
.gitignore Remove non-project specific entry from gitignore 2021-03-22 22:02:00 +00:00
.rubocop.yml Extract ActiveStorage::Streaming so your own controllers can use it (#41440) 2021-02-19 15:40:56 +01:00
.yardopts
.yarnrc
Brewfile Address Error: caskroom/cask was moved. Tap homebrew/cask-cask instead. 2019-12-18 18:50:57 +09:00
CODE_OF_CONDUCT.md
CONTRIBUTING.md Adding badges and logo to README and CONTRIBUTING page 2021-01-20 10:53:47 +01:00
Gemfile Merge pull request #41550 from p8/sdoc-2.0.4 2021-02-25 18:37:04 +01:00
Gemfile.lock Make sure the version of rake used in Rails apps work 2021-03-15 20:48:38 +00:00
MIT-LICENSE Bump license years to 2021 [ci skip] 2021-01-01 12:21:20 +09:00
package.json
rails.gemspec Rails 7 requires Ruby 2.7 and prefer Ruby 3+ 2021-02-04 16:34:53 +00:00
RAILS_VERSION Rails 6.2 is now Rails 7.0 2021-02-04 16:47:16 +00:00
Rakefile
README.md Adding badges and logo to README and CONTRIBUTING page 2021-01-20 10:53:47 +01:00
RELEASING_RAILS.md Rename master to main in all code references 2021-01-19 20:46:33 +00:00
version.rb Rails 6.2 is now Rails 7.0 2021-02-04 16:47:16 +00:00
yarn.lock Upgrade kind-of 2020-04-19 23:59:27 -03:00

Welcome to Rails

What's Rails?

Rails is a web-application framework that includes everything needed to create database-backed web applications according to the Model-View-Controller (MVC) pattern.

Understanding the MVC pattern is key to understanding Rails. MVC divides your application into three layers: Model, View, and Controller, each with a specific responsibility.

Model layer

The Model layer represents the domain model (such as Account, Product, Person, Post, etc.) and encapsulates the business logic specific to your application. In Rails, database-backed model classes are derived from ActiveRecord::Base. Active Record allows you to present the data from database rows as objects and embellish these data objects with business logic methods. Although most Rails models are backed by a database, models can also be ordinary Ruby classes, or Ruby classes that implement a set of interfaces as provided by the Active Model module.

Controller layer

The Controller layer is responsible for handling incoming HTTP requests and providing a suitable response. Usually, this means returning HTML, but Rails controllers can also generate XML, JSON, PDFs, mobile-specific views, and more. Controllers load and manipulate models, and render view templates in order to generate the appropriate HTTP response. In Rails, incoming requests are routed by Action Dispatch to an appropriate controller, and controller classes are derived from ActionController::Base. Action Dispatch and Action Controller are bundled together in Action Pack.

View layer

The View layer is composed of "templates" that are responsible for providing appropriate representations of your application's resources. Templates can come in a variety of formats, but most view templates are HTML with embedded Ruby code (ERB files). Views are typically rendered to generate a controller response or to generate the body of an email. In Rails, View generation is handled by Action View.

Frameworks and libraries

Active Record, Active Model, Action Pack, and Action View can each be used independently outside Rails. In addition to that, Rails also comes with Action Mailer, a library to generate and send emails; Action Mailbox, a library to receive emails within a Rails application; Active Job, a framework for declaring jobs and making them run on a variety of queuing backends; Action Cable, a framework to integrate WebSockets with a Rails application; Active Storage, a library to attach cloud and local files to Rails applications; Action Text, a library to handle rich text content; and Active Support, a collection of utility classes and standard library extensions that are useful for Rails, and may also be used independently outside Rails.

Getting Started

  1. Install Rails at the command prompt if you haven't yet:

     $ gem install rails
    
  2. At the command prompt, create a new Rails application:

     $ rails new myapp
    

    where "myapp" is the application name.

  3. Change directory to myapp and start the web server:

     $ cd myapp
     $ bin/rails server
    

    Run with --help or -h for options.

  4. Go to http://localhost:3000 and you'll see: "Yay! Youre on Rails!"

  5. Follow the guidelines to start developing your application. You may find the following resources handy:

Contributing

We encourage you to contribute to Ruby on Rails! Please check out the Contributing to Ruby on Rails guide for guidelines about how to proceed. Join us!

Trying to report a possible security vulnerability in Rails? Please check out our security policy for guidelines about how to proceed.

Everyone interacting in Rails and its sub-projects' codebases, issue trackers, chat rooms, and mailing lists is expected to follow the Rails code of conduct.

License

Ruby on Rails is released under the MIT License.