未初始化的常量 Mysql::error答案

【问题标题】：uninitialized constant Mysql::error未初始化的常量 Mysql::error
【发布时间】：2011-09-06 13:14:25
【问题描述】：

我正在尝试将我的 rails 应用程序投入生产，但这是我的第一次。我正在运行 mysql 5.5 和 gem 2.8.1。

在尝试 rake db:setup RAILS_ENV="production" 时，我得到以下信息：

rake aborted!
uninitialized constant Mysql::Error

非常感谢任何帮助

我认为添加此错误的跟踪文件可能很有用。任何帮助将不胜感激：

rake db:setup RAILS_ENV="production" --trace
(in /Users/chris/rails_projects/sienab)
** Invoke db:setup (first_time)
** Invoke db:create (first_time)
** Invoke db:load_config (first_time)
** Invoke rails_env (first_time)
** Execute rails_env
** Execute db:load_config
** Execute db:create
rake aborted!
uninitialized constant Mysql::Error
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.6/lib/active_record/railties/databases.rake:64:in `create_database'
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.6/lib/active_record/railties/databases.rake:35
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:607:in `invoke_prerequisites'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:604:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:604:in `invoke_prerequisites'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:596:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/bin/rake:31
/usr/bin/rake:19:in `load'
/usr/bin/rake:19

【问题讨论】：

标签： mysql ruby-on-rails rake

【解决方案1】：

如Rails 3 Mysql Problems 中所述，如果可能，您应该使用mysql2 gem。

确保在 Gemfile 和 database.yml 中将 mysql 更改为 mysql2

【讨论】：

【解决方案2】：

实际的错误是关于 Mysql::Error 常量。

你在 Gemfile 中包含 mysql gem 吗？

你在database.yml中使用mysql吗？

【讨论】：

在 gemfile 中我有：group :production do gem 'mysql' end