rails3 rake db：迁移错误答案

【问题标题】：rails3 rake db:migrate errorrails3 rake db：迁移错误
【发布时间】：2011-09-17 14:01:33
【问题描述】：

直升机，

我正在尝试使用 mysql2 gem 为我的 rails 3 应用程序运行 rake db:migrate。但最终出现以下错误。你有什么主意吗？谢谢

WARNING: This version of mysql2 (0.3.7) doesn't ship with the ActiveRecord adapter bundled anymore as it's now part of Rails 3.1
WARNING: Please use the 0.2.x releases if you plan on using it in Rails <= 3.0.x
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:4: warning: already initialized constant MAJOR
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:5: warning: already initialized constant MINOR
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:6: warning: already initialized constant BUILD
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:3: warning: already initialized constant NUMBERS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/version.rb:9: warning: already initialized constant VERSION
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake.rb:26: warning: already initialized constant RAKEVERSION
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/early_time.rb:17: warning: already initialized constant EARLY
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/alt_system.rb:32: warning: already initialized constant WINDOWS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/application.rb:28: warning: already initialized constant DEFAULT_RAKEFILES
WARNING: Possible conflict with Rake extension: String#ext already exists
WARNING: Possible conflict with Rake extension: String#pathmap already exists
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/task_arguments.rb:73: warning: already initialized constant EMPTY_TASK_ARGS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/invocation_chain.rb:49: warning: already initialized constant EMPTY
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_utils.rb:10: warning: already initialized constant RUBY
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_utils.rb:84: warning: already initialized constant LN_SUPPORTED
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/dsl_definition.rb:143: warning: already initialized constant Commands
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:44: warning: already initialized constant ARRAY_METHODS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:47: warning: already initialized constant MUST_DEFINE
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:51: warning: already initialized constant MUST_NOT_DEFINE
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:55: warning: already initialized constant SPECIAL_RETURN
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:61: warning: already initialized constant DELEGATING_METHODS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:364: warning: already initialized constant DEFAULT_IGNORE_PATTERNS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake/file_list.rb:370: warning: already initialized constant DEFAULT_IGNORE_PROCS
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake.rb:64: warning: already initialized constant FileList
/Users/Sako/.rvm/gems/ruby-1.9.2-p290@global/gems/rake-0.9.2/lib/rake.rb:65: warning: already initialized constant RakeFileUtils
rake aborted!
stack level too deep

【问题讨论】：

您使用的是什么版本的 Rails gem？

标签： ruby-on-rails mysql2

【解决方案1】：

答案在错误信息中：

 WARNING: Please use the 0.2.x releases if you plan on using it in Rails <= 3.0.x

只需修复 gemfile 中的 mysql 版本 :)

【讨论】：

嗨apneadiving，感谢您的建议。我已将 mysql gem 降级到 0.2.7 ，但是在运行 rake db:migrate 时它问我 0.3.7 并建议我运行 bundle install.. 回到零
你的 rails 和 arel 版本是什么？
我在 GemFile 中添加了 gem 'mysql2', '0.2.7'，前 2 行警告消失了，但是后面的错误行仍然相同.. :(
嗨，apneadiving，我在这里找到了答案stackoverflow.com/questions/3456304/…，即通过运行 bundle exed rake db:migrate，原因是 ruby 版本不兼容.. 在 mac 中安装 mysql 真的很痛苦（可能只适用于我）。感谢apneadiving
我以为你已经在使用这个命令了 :) 如果它有帮助，请考虑接受这个答案。

【解决方案2】：

检查 GemFile，只需将 rails 版本从 3.0.0 编辑到 3.1.0，不关心 mysql 版本，保持 0.3.7，您不必降级

【讨论】：