[RUBY] [Rails] rails new to create a database with PostgreSQL


This year, I'm trying to challenge the Web little by little, so I'm messing with Rails, which seems to have the most references. For the time being, I've finished building a local environment and are trying various things with Rails new. I'm writing an article with the hope that I'd like to organize my mind once and make it into a template, and I'd be happy if you could point out any mistakes. I hope it will be helpful for those who are having trouble with Rails new.



ruby 2.6.6
psql (PostgreSQL) 12.3

I will not write about environment construction, so please check if necessary. Change the database to PostgreSQL. And gems are basically put locally. It seems that either one is fine, but somehow it does.

Create a Gemfile in your application's directory

Please create a directory appropriately.


C:\Users\user\sample_app> bundle init

Describe the gem to be added to the Gemfile

Open the created Gemfile with an editor and add the following.


gem 'rails'//Comment out(#)Just remove
gem 'pg'//When changing to PostgreSQL

I'm not sure if I should specify the gem version, so I won't specify it for the time being.

bundle install


bundle install --path vendor/bundle

--path vendor / bundle is specified when installing the gem locally. This seems to install the gem in vendor / bundle. It seems that --path vendor / bundle can be omitted by specifying only the first time.

rails new


bundle exec rails new . -d postgresql --skip-turbolinks --skip-test

bundle exec is attached when Rails is installed locally. After that, attach it to all rails commands. -d postgresql --skip-turbolinks --skip-test seems to have many other options, so check it out if necessary. There are many things I don't understand, so I'll just write what everyone is writing.

Create a database in SQL Shell


create role APPLICATION_NAME with createdb login password 'PASSWORD';
select * from pg_user;

Enter your user name (app name) in APPLICATION_NAME and any password in PASSWORD. Check if the role has been created with select * from pg_user ;.

Update database.yml

Write the following in database.yml in the config folder.


default: &default
  adapter: postgresql
  encoding: unicode
  # For details on connection pooling, see Rails configuration guide
  # https://guides.rubyonrails.org/configuring.html#database-pooling
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

  username: APPLICATION_NAME//add to(Username decided when creating the database)
  password: PASSWORD//add to(Password decided when creating the database)
  host: localhost//add to

After saving database.yml, update the database as well.


bundle exec rails db:migrate:reset

Start the server


bundle exec rails s

In your browser http: // localhost: 3000 / If you access and the image is displayed, it is successful.


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