Rails new project generation - Performance & Optimization

Performance: Rails new project generation

MEDIUM IMPACT

This affects the initial load speed and bundle size of a Rails web application by determining which components and assets are included from the start.

Creating a new Rails project with only needed components

Ruby on Rails

rails new myapp --skip-action-mailbox --skip-action-text --skip-active-storage --skip-javascript

Skips unused components, reducing bundle size and asset compilation time, leading to faster initial page load.

📈 Performance GainSaves 500-1000KB in assets, reduces LCP by 200-400ms

Creating a new Rails project with only needed components

Ruby on Rails

rails new myapp

Generates a full Rails app with all default components, including unused JavaScript frameworks, CSS, and Active Storage, increasing bundle size and load time.

📉 Performance CostAdds 1-2MB to initial bundle size, increasing LCP by 300-500ms on slow networks

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Full default Rails project	Moderate (default views and scripts)	Multiple reflows due to larger CSS/JS	Higher paint cost from bigger assets	[X] Bad
Rails project with skipped unused components	Minimal DOM from leaner views	Single reflow from optimized CSS/JS	Lower paint cost due to smaller assets	[OK] Good

Rendering Pipeline

The Rails new project generation determines which assets and code are included in the initial HTML, CSS, and JavaScript sent to the browser. More components mean more files to compile and send, affecting the browser's parsing and rendering speed.

→Network Transfer

→HTML Parsing

→CSSOM Construction

→JavaScript Execution

⚠️ BottleneckNetwork Transfer and JavaScript Execution due to larger asset bundles

Core Web Vital Affected

LCP

This affects the initial load speed and bundle size of a Rails web application by determining which components and assets are included from the start.

Optimization Tips

1Skip unused Rails components to reduce initial asset size.

2Smaller bundles improve Largest Contentful Paint (LCP).

3Avoid including unnecessary JavaScript frameworks at project start.

Performance Quiz - 3 Questions

What is a performance downside of generating a Rails project with all default components?

A It reduces the number of HTTP requests

B It improves JavaScript execution speed

C Larger initial asset size increases page load time

D It decreases CSS complexity

DevTools: Network

How to check: Open DevTools, go to Network tab, reload the page, and observe the size and number of asset files loaded.

What to look for: Look for large JavaScript and CSS files that delay page load; smaller bundles indicate better performance.

Practice

1. What does the rails new command do when creating a new project?

easy

A. It only installs Rails without creating any files.

B. It creates a new Rails app with all necessary files and folders.

C. It deletes old Rails projects from your computer.

D. It updates an existing Rails app to the latest version.

Solution

1. Step 1: Understand the purpose of rails new

   This command is designed to set up a new Rails application by creating all the needed files and folders automatically.

2. Step 2: Compare options

   Options A, C, and D describe actions unrelated to creating a new project. Only It creates a new Rails app with all necessary files and folders. correctly describes the creation of a new app with files.

3. Final Answer:

   It creates a new Rails app with all necessary files and folders. -> Option B

4. Quick Check:

   rails new creates app files = B [OK]

Hint: Remember: rails new sets up a full app folder [OK]

Common Mistakes:

• Thinking it only installs Rails without files
• Confusing it with update or delete commands
• Assuming it modifies existing projects

2. Which of the following is the correct syntax to create a new Rails project named blog with PostgreSQL as the database?

easy

A. rails new blog -d mysql

B. rails create blog --db=postgresql

C. rails generate blog --database=postgresql

D. rails new blog --database=postgresql

Solution

1. Step 1: Identify the correct command for new project creation

   The command to create a new Rails app is rails new, not rails create or rails generate.

2. Step 2: Check the database option syntax

   The correct option to specify the database is --database=postgresql. rails new blog -d mysql uses -d mysql which is for MySQL, not PostgreSQL.

3. Final Answer:

   rails new blog --database=postgresql -> Option D

4. Quick Check:

   Use rails new with --database= option = C [OK]

Hint: Use rails new appname --database=postgresql for PostgreSQL [OK]

Common Mistakes:

• Using rails create instead of rails new
• Wrong database option like -d mysql for PostgreSQL
• Confusing rails generate with project creation

3. After running rails new shop, which folder will NOT be created inside the new shop directory?

medium

A. app

B. bin

C. node_modules

D. config

Solution

1. Step 1: Recall default folders created by rails new

   Rails creates folders like app, bin, and config by default for app code, executables, and configuration.

2. Step 2: Understand node_modules folder creation

   The node_modules folder is created only after installing JavaScript packages with tools like Yarn or npm, not by default with rails new.

3. Final Answer:

   node_modules -> Option C

4. Quick Check:

   node_modules appears after JS install, not on new app [OK]

Hint: Default Rails folders exclude node_modules until JS packages installed [OK]

Common Mistakes:

• Assuming node_modules is created by default
• Confusing bin with temporary folders
• Not knowing which folders Rails generates automatically

4. You ran rails new myapp --database=sqlite3 but got an error saying the database adapter is missing. What is the most likely cause?

medium

A. You forgot to install the SQLite3 gem before creating the project.

B. The command rails new does not support SQLite3 database.

C. You must use --db=sqlite3 instead of --database=sqlite3.

D. You need to create the database manually before running rails new.

Solution

1. Step 1: Understand the error cause

   The error about missing database adapter usually means the required gem (SQLite3) is not installed on the system.

2. Step 2: Check command and options validity

   The rails new command supports SQLite3 by default with --database=sqlite3. The option --db= is invalid, and manual DB creation is not needed before project creation.

3. Final Answer:

   You forgot to install the SQLite3 gem before creating the project. -> Option A

4. Quick Check:

   Missing DB adapter error = missing gem install [OK]

Hint: Install DB gems before rails new to avoid adapter errors [OK]

Common Mistakes:

• Using wrong option --db= instead of --database=
• Thinking rails new can't use SQLite3
• Trying to create DB manually before project

5. You want to create a new Rails project named portfolio with PostgreSQL and skip the default test framework. Which command should you use?

hard

A. rails new portfolio --database=postgresql --skip-test

B. rails new portfolio -d postgresql --skip-test-framework

C. rails new portfolio --database=postgresql --skip-test-framework

D. rails new portfolio -d postgresql --skip-test

Solution

1. Step 1: Identify correct database option

   The shorthand for --database is -d, but both -d postgresql and --database=postgresql are valid.

2. Step 2: Identify correct option to skip test framework

   The correct option to skip the default test framework is --skip-test. The option --skip-test-framework is invalid.

3. Step 3: Combine correct options

   Both rails new portfolio -d postgresql --skip-test and rails new portfolio --database=postgresql --skip-test are valid, but the official documentation prefers the full option --database= with --skip-test.

4. Final Answer:

   rails new portfolio --database=postgresql --skip-test -> Option A

5. Quick Check:

   Use --database= for DB and --skip-test to skip tests [OK]

Hint: Use --database= for DB and --skip-test to skip tests [OK]

Common Mistakes:

• Using invalid option --skip-test-framework
• Using shorthand -d with wrong skip option
• Mixing shorthand and wrong skip flags