Heroku is giving 'Specified 'sqlite3' for database adapter, but the gem is not loaded'

Question

Gemfile

source 'https://rubygems.org'

git_source(:github) do |repo_name|
  repo_name = "#{repo_name}/#{repo_name}" unless repo_name.include?("/")
  "https://github.com/#{repo_name}.git"
end


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.1.5'
# Use Puma as the app server
gem 'puma', '~> 3.7'
# 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 'therubyracer', platforms: :ruby

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

group :development, :test do
  # Use sqlite3 as the database for Active Record
  gem 'sqlite3'
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '~> 2.13'
  gem 'selenium-webdriver'
end

group :development do
  # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
  gem 'web-console', '>= 3.3.0'
  gem 'listen', '>= 3.0.5', '< 3.2'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'
end

group :production do
  gem 'pg'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    actioncable (5.1.5)
      actionpack (= 5.1.5)
      nio4r (~> 2.0)
      websocket-driver (~> 0.6.1)
    actionmailer (5.1.5)
      actionpack (= 5.1.5)
      actionview (= 5.1.5)
      activejob (= 5.1.5)
      mail (~> 2.5, >= 2.5.4)
      rails-dom-testing (~> 2.0)
    actionpack (5.1.5)
      actionview (= 5.1.5)
      activesupport (= 5.1.5)
      rack (~> 2.0)
      rack-test (>= 0.6.3)
      rails-dom-testing (~> 2.0)
      rails-html-sanitizer (~> 1.0, >= 1.0.2)
    actionview (5.1.5)
      activesupport (= 5.1.5)
      builder (~> 3.1)
      erubi (~> 1.4)
      rails-dom-testing (~> 2.0)
      rails-html-sanitizer (~> 1.0, >= 1.0.3)
    activejob (5.1.5)
      activesupport (= 5.1.5)
      globalid (>= 0.3.6)
    activemodel (5.1.5)
      activesupport (= 5.1.5)
    activerecord (5.1.5)
      activemodel (= 5.1.5)
      activesupport (= 5.1.5)
      arel (~> 8.0)
    activesupport (5.1.5)
      concurrent-ruby (~> 1.0, >= 1.0.2)
      i18n (~> 0.7)
      minitest (~> 5.1)
      tzinfo (~> 1.1)
    addressable (2.5.2)
      public_suffix (>= 2.0.2, < 4.0)
    arel (8.0.0)
    bindex (0.5.0)
    builder (3.2.3)
    byebug (10.0.0)
    capybara (2.18.0)
      addressable
      mini_mime (>= 0.1.3)
      nokogiri (>= 1.3.3)
      rack (>= 1.0.0)
      rack-test (>= 0.5.4)
      xpath (>= 2.0, < 4.0)
    childprocess (0.8.0)
      ffi (~> 1.0, >= 1.0.11)
    coffee-rails (4.2.2)
      coffee-script (>= 2.2.0)
      railties (>= 4.0.0)
    coffee-script (2.4.1)
      coffee-script-source
      execjs
    coffee-script-source (1.12.2)
    concurrent-ruby (1.0.5)
    crass (1.0.3)
    erubi (1.7.1)
    execjs (2.7.0)
    ffi (1.9.23)
    globalid (0.4.1)
      activesupport (>= 4.2.0)
    i18n (0.9.5)
      concurrent-ruby (~> 1.0)
    jbuilder (2.7.0)
      activesupport (>= 4.2.0)
      multi_json (>= 1.2)
    listen (3.1.5)
      rb-fsevent (~> 0.9, >= 0.9.4)
      rb-inotify (~> 0.9, >= 0.9.7)
      ruby_dep (~> 1.2)
    loofah (2.2.0)
      crass (~> 1.0.2)
      nokogiri (>= 1.5.9)
    mail (2.7.0)
      mini_mime (>= 0.1.1)
    method_source (0.9.0)
    mini_mime (1.0.0)
    mini_portile2 (2.3.0)
    minitest (5.11.3)
    multi_json (1.13.1)
    nio4r (2.2.0)
    nokogiri (1.8.2)
      mini_portile2 (~> 2.3.0)
    pg (1.0.0)
    public_suffix (3.0.2)
    puma (3.11.3)
    rack (2.0.4)
    rack-test (0.8.3)
      rack (>= 1.0, < 3)
    rails (5.1.5)
      actioncable (= 5.1.5)
      actionmailer (= 5.1.5)
      actionpack (= 5.1.5)
      actionview (= 5.1.5)
      activejob (= 5.1.5)
      activemodel (= 5.1.5)
      activerecord (= 5.1.5)
      activesupport (= 5.1.5)
      bundler (>= 1.3.0)
      railties (= 5.1.5)
      sprockets-rails (>= 2.0.0)
    rails-dom-testing (2.0.3)
      activesupport (>= 4.2.0)
      nokogiri (>= 1.6)
    rails-html-sanitizer (1.0.3)
      loofah (~> 2.0)
    railties (5.1.5)
      actionpack (= 5.1.5)
      activesupport (= 5.1.5)
      method_source
      rake (>= 0.8.7)
      thor (>= 0.18.1, < 2.0)
    rake (12.3.0)
    rb-fsevent (0.10.3)
    rb-inotify (0.9.10)
      ffi (>= 0.5.0, < 2)
    ruby_dep (1.5.0)
    rubyzip (1.2.1)
    sass (3.5.5)
      sass-listen (~> 4.0.0)
    sass-listen (4.0.0)
      rb-fsevent (~> 0.9, >= 0.9.4)
      rb-inotify (~> 0.9, >= 0.9.7)
    sass-rails (5.0.7)
      railties (>= 4.0.0, < 6)
      sass (~> 3.1)
      sprockets (>= 2.8, < 4.0)
      sprockets-rails (>= 2.0, < 4.0)
      tilt (>= 1.1, < 3)
    selenium-webdriver (3.10.0)
      childprocess (~> 0.5)
      rubyzip (~> 1.2)
    spring (2.0.2)
      activesupport (>= 4.2)
    spring-watcher-listen (2.0.1)
      listen (>= 2.7, < 4.0)
      spring (>= 1.2, < 3.0)
    sprockets (3.7.1)
      concurrent-ruby (~> 1.0)
      rack (> 1, < 3)
    sprockets-rails (3.2.1)
      actionpack (>= 4.0)
      activesupport (>= 4.0)
      sprockets (>= 3.0.0)
    sqlite3 (1.3.13)
    thor (0.20.0)
    thread_safe (0.3.6)
    tilt (2.0.8)
    turbolinks (5.1.0)
      turbolinks-source (~> 5.1)
    turbolinks-source (5.1.0)
    tzinfo (1.2.5)
      thread_safe (~> 0.1)
    uglifier (4.1.6)
      execjs (>= 0.3.0, < 3)
    web-console (3.5.1)
      actionview (>= 5.0)
      activemodel (>= 5.0)
      bindex (>= 0.4.0)
      railties (>= 5.0)
    websocket-driver (0.6.5)
      websocket-extensions (>= 0.1.0)
    websocket-extensions (0.1.3)
    xpath (3.0.0)
      nokogiri (~> 1.8)

PLATFORMS
  ruby

DEPENDENCIES
  byebug
  capybara (~> 2.13)
  coffee-rails (~> 4.2)
  jbuilder (~> 2.5)
  listen (>= 3.0.5, < 3.2)
  pg
  puma (~> 3.7)
  rails (~> 5.1.5)
  sass-rails (~> 5.0)
  selenium-webdriver
  spring
  spring-watcher-listen (~> 2.0.0)
  sqlite3
  turbolinks (~> 5)
  tzinfo-data
  uglifier (>= 1.3.0)
  web-console (>= 3.3.0)

BUNDLED WITH
   1.16.1

Committed my changes and pushed them. Then, I have pushed the master branch to Heroku with git push heroku but I'm still getting:

/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.5/lib/active_record/connection_adapters/connection_specification.rb:188:in `rescue in spec': Specified 'sqlite3' for database adapter, but the gem is not loaded. Add `gem 'sqlite3'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord). (Gem::LoadError)

when I want to restart my dyno at Heroku.

Answer 1

The production block for your database in database.yml should look something like this, change out the xxxx with your matching values which should already be in the file, they should be in the other blocks (production, test). The adapter needs to be changed.

production:
  adapter:  postgresql <--- This is the important part
  encoding: unicode
  database: xxxxxxx
  username: xxxxxxx
  password: <%= ENV['xxxxxx'] %>