首先，请原谅我在Ruby中缺乏知识，而且我很可能在整篇文章中滥用某些术语;我对此非常陌生，而且我几乎没有掌握所有内容。
OS：Mac os X El Capitan
无论如何，我正在关注“The Odin Project”，这是对Web开发程序的介绍，我一直在仔细地关注每一步，直到它在终端中执行以下命令为止
heroku run rails db:migrate
我得到了一堆错误
Running rails db:migrate on ⬢ floating-falls-25848... up, run.9253 (Free)
rails aborted!
Gem::LoadError: 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).
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:188:in `rescue in spec'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:185:in `spec'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:880:in `establish_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:58:in `establish_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/railtie.rb:124:in `block (2 levels) in <class:Railtie>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `instance_eval'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `block in execute_hook'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:60:in `with_execution_control'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:65:in `execute_hook'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `each'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/base.rb:326:in `<module:ActiveRecord>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/base.rb:25:in `<top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:6:in `<class:MySQLDatabaseTasks>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:3:in `<module:Tasks>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:2:in `<module:ActiveRecord>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:1:in `<top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:74:in `<module:DatabaseTasks>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:35:in `<module:Tasks>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:2:in `<module:ActiveRecord>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:1:in `<top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/railtie.rb:34:in `block (3 levels) in <class:Railtie>'
/app/vendor/bundle/ruby/2.3.0/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:21:in `block in perform'
/app/vendor/bundle/ruby/2.3.0/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:18:in `perform'
/app/vendor/bundle/ruby/2.3.0/gems/railties-5.1.4/lib/rails/command.rb:46:in `invoke'
/app/vendor/bundle/ruby/2.3.0/gems/railties-5.1.4/lib/rails/commands.rb:16:in `<top (required)>'
/app/bin/rails:9:in `require'
/app/bin/rails:9:in `<main>'
Caused by:
Gem::LoadError: sqlite3 is not part of the bundle. Add it to your Gemfile.
/app/vendor/bundle/ruby/2.3.0/gems/bundler-1.15.2/lib/bundler/rubygems_integration.rb:377:in `block (2 levels) in replace_gem'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/connection_adapters/sqlite3_adapter.rb:10:in `<top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/connection_adapters/connection_specification.rb:186:in `spec'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:880:in `establish_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/connection_handling.rb:58:in `establish_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/railtie.rb:124:in `block (2 levels) in <class:Railtie>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `instance_eval'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:69:in `block in execute_hook'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:60:in `with_execution_control'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:65:in `execute_hook'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:50:in `block in run_load_hooks'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `each'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/lazy_load_hooks.rb:49:in `run_load_hooks'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/base.rb:326:in `<module:ActiveRecord>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/base.rb:25:in `<top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:6:in `<class:MySQLDatabaseTasks>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:3:in `<module:Tasks>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:2:in `<module:ActiveRecord>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/mysql_database_tasks.rb:1:in `<top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:74:in `<module:DatabaseTasks>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:35:in `<module:Tasks>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:2:in `<module:ActiveRecord>'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/tasks/database_tasks.rb:1:in `<top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `block in require'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:258:in `load_dependency'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.1.4/lib/active_support/dependencies.rb:292:in `require'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.4/lib/active_record/railtie.rb:34:in `block (3 levels) in <class:Railtie>'
/app/vendor/bundle/ruby/2.3.0/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:21:in `block in perform'
/app/vendor/bundle/ruby/2.3.0/gems/railties-5.1.4/lib/rails/commands/rake/rake_command.rb:18:in `perform'
/app/vendor/bundle/ruby/2.3.0/gems/railties-5.1.4/lib/rails/command.rb:46:in `invoke'
/app/vendor/bundle/ruby/2.3.0/gems/railties-5.1.4/lib/rails/commands.rb:16:in `<top (required)>'
/app/bin/rails:9:in `require'
/app/bin/rails:9:in `<main>'
Tasks: TOP => db:migrate => db:load_config
(See full trace by running task with --trace)
知道可能导致此问题的原因是什么？
这是我的Gemfile文件的样子：
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
ruby '2.3.4'
# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.1.4'
# Use sqlite3 as the database for Active Record
group :development, :test do
gem 'sqlite3'
end
group :production do
gem 'pg'
end
（只是代码的一部分，以显示'sqlite3'的位置）
编辑：这是我的database.ysml文件的样子：
# SQLite version 3.x
# gem install sqlite3
#
# Ensure the SQLite 3 gem is defined in your Gemfile
# gem 'sqlite3'
#
default: &default
adapter: sqlite3
pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
timeout: 5000
development:
<<: *default
database: db/development.sqlite3
# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
<<: *default
database: db/test.sqlite3
production:
<<: *default
database: db/production.sqlite3
答案 0 :(得分：0)
您在config/database.yml中错误地设置了数据库和适配器。
下面：
default: &default
adapter: sqlite3
pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
timeout: 5000
您指定的默认数据库适配器是sqlite3。然后，在生产中，你做：
production:
<<: *default
database: db/production.sqlite3
了解您从未指定adapter:值的方式？这意味着您使用的是default中sqlite3设置的db/production.sqlite3。
此外，您还要指定要在生产中使用的数据库是production:
<<: *default
adapter: postgresql
database: contacts_production
username: contacts
password: <%= ENV['CONTACTS_DATABASE_PASSWORD'] %>
，这自然是不正确的。
您的生产配置应该更像：
adapter: postgresql看看它是怎么说的，postgresql？这将覆盖您的默认值。因此，在生产中（在Heroku上），您被配置为使用sqlite3而不是database:。
当然，您需要自己的username:，password:和<!DOCTYPE html>
<html>
<body>
<left>
<a id="myAnchor" download="image.jpg"><b><u>Download</u></b></a>
</left>
<img crossOrigin="anonymous" src="http://i1213.photobucket.com/albums/cc475/kmkcorp/TigsMoney1_zpst9wv6cdb.jpg" id="img" style="display:none" alt="picture"/></image>
<canvas id="canvas" width="1600" height="1600" style="border:0px;"></canvas>
<script type="text/javascript">
window.onload = function() {
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var img = document.getElementById("img");
ctx.drawImage(img, canvas.width / 2 - img.width / 2, canvas.height / 2 - img.height / 2);
ctx.canvas.toBlob(function(blob){
myAnchor.href = URL.createObjectURL(blob);});
var revokeURL=function(){
requestAnimationFrame(function(){
URL.revokeObjectURL(this.href);
this.href=null;});
this.removeEventListener('click', revokeURL);};
myanchor.addEventListener('click', revokeURL);};
img.src="http://i1213.photobucket.com/albums/cc475/kmkcorp/TigsMoney1_zpst9wv6cdb.jpg";
</script>
</body>
</html>
（我刚刚从我的某个项目中提取了一些内容）。这可能并不完全正确，所以你不得不对此大惊小怪。
此外，如果您有选项，则应该对所有环境使用postgresql。数据库存在微妙（而不是那么微妙）的差异，您只需在不同的环境中使用不同的数据库就可以让自己心痛。