Rails herokuでデプロイしてApplication errorが出たのでコンソールを開くとLoadErrorが出た

Question

Railsで、herokuでデプロイして、＄heroku openで、URLにジャンプするとapplication errorが出たので、その画面に記載してあった通り

$heroku logs --tail

を打つと、

2020-08-08T13:08:51.475256+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=yushiiiiii.herokuapp.com request_id=745f6c2b-93c4-485a-9264-a7a98ed29657 fwd="106.180.8.204" dyno= connect= service= status=503 bytes= protocol=https
2020-08-08T13:08:52.309256+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=yushiiiiii.herokuapp.com request_id=d3bfad29-795c-4fef-bedb-a1732cae3c0a fwd="106.180.8.204" dyno= connect= service= status=503 bytes= protocol=https

と、エラーが出ました。
コンソールを開くと良いと調べると出たので、原因らしきエラーが出ました。

$heroku run rails c

エラー内容

/app/vendor/bundle/ruby/2.6.0/gems/bundler-2.0.2/lib/bundler/rubygems_integration.rb:406:in `block (2 levels) in replace_gem': Error loading the 'postgresql' Active Record adapter. Missing a gem it depends on? pg is not part of the bundle. Add it to your Gemfile. (LoadError)

gemに問題があるようなのですが、解決法がわかりません。作成環境はWindowsです。
Gemfileのコードも載せておきます。どうかよろしくお願いします。

source "https://rubygems.org"
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby "2.6.6"

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem "rails", "~> 5.2.4", ">= 5.2.4.3"
# Use sqlite3 as the database for Active Record
#gem "sqlite3"
# Use Puma as the app server
gem "puma", "~> 3.11"
# Use SCSS for stylesheets
gem "sass-rails", "~> 5.0"
# Use Uglifier as compressor for JavaScript assets
gem "uglifier", ">= 1.3.0"
# See https://github.com/rails/execjs#readme for more supported runtimes
gem "duktape"
# Use CoffeeScript for .coffee assets and views
gem "coffee-rails", "~> 4.2"
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem "turbolinks", "~> 5"
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem "jbuilder", "~> 2.5"
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 4.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use ActiveStorage variant
# gem 'mini_magick', '~> 4.8'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

# Reduces boot times through caching; required in config/boot.rb
gem "bootsnap", ">= 1.1.0", require: false

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem "byebug", platforms: [:mri, :mingw, :x64_mingw]
  gem "sqlite3", "1.3.13"
end

group :development do
  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
  gem "web-console", ">= 3.3.0"
end

group :test do
  # Adds support for Capybara system testing and selenium driver
  gem "capybara", ">= 2.15"
  gem "selenium-webdriver"
  # Easy installation and use of chromedriver to run system tests with Chrome
  gem "chromedriver-helper"
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem "tzinfo-data", platforms: [:mingw, :mswin, :x64_mingw, :jruby]
group :production do
  gem "pg", "0.20.0"
end

よろしくお願いいたします.

Answer 1

/app/vendor/bundle/ruby/2.6.0/gems/bundler-2.0.2/lib/bundler/rubygems_integration.rb:406:in `block (2 levels) in replace_gem': Error loading the 'postgresql' Active Record adapter. Missing a gem it depends on? pg is not part of the bundle. Add it to your Gemfile. (LoadError)

上記のエラーは、データベースに接続しようとしたとき、
pg という PostgreSQL への接続に必要な RubyGem がないので接続できなかったことを示しています

Gemfile は production 向けの設定に pg が定義できているようです

Heroku では特に設定を変更しない限り、
git push 時に bundle install が production 向けに実行されます

Managing Gems with Bundler | Heroku Dev Center
Rails 5.x applications | Heroku Ruby Support | Heroku Dev Center

次の記述を行った .bundle/config を Heroku に git push してしまうと
production 向けの RubyGem はインストールされませんので注意が必要です:

BUNDLE_WITHOUT: "production"

参考: heroku run rails db:migrateの時にpg is not part of the bundle - Qiita