Ruby on Rails mysql2 适配器问题答案

【问题标题】：Ruby on Rails mysql2 adapter problemRuby on Rails mysql2 适配器问题
【发布时间】：2011-09-18 10:38:16
【问题描述】：

我已经安装了 ruby 和 rails，当我尝试运行时，我的应用程序给了我一个错误

rake db:迁移

这是命令 rake db:migrate --trace 的结果

** Execute db:migrate
rake aborted!
!!! Missing the mysql2 gem. Add it to your Gemfile: gem 'mysql2'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/mysql_adapter.rb:22:in `rescue in mysql_connection'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/mysql_adapter.rb:19:in `mysql_connection'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:229:in `new_connection'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:237:in `checkout_new_connection'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:191:in `block (2 levels) in checkout'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:187:in `loop'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:187:in `block in checkout'
/usr/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:186:in `checkout'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:94:in `connection'
/usr/lib/ruby/gems/1.9.1/gems/ar-octopus-0.3.4/lib/octopus/proxy.rb:83:in `select_connection'
/usr/lib/ruby/gems/1.9.1/gems/ar-octopus-0.3.4/lib/octopus/proxy.rb:177:in `send_queries_to_selected_slave'
/usr/lib/ruby/gems/1.9.1/gems/ar-octopus-0.3.4/lib/octopus/proxy.rb:140:in `method_missing'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:454:in `get_all_versions'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:583:in `migrated'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:492:in `current_version'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:509:in `block in migrate'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:509:in `each'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:509:in `detect'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:509:in `migrate'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:433:in `up'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/migration.rb:415:in `migrate'
/usr/lib/ruby/gems/1.9.1/gems/activerecord-3.0.6/lib/active_record/railties/databases.rake:142:in `block (2 levels) in <top (required)>'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:636:in `block in execute'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:597:in `block in invoke_with_call_chain'
/usr/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:2029:in `block (2 levels) in top_level'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:2029:in `block in top_level'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:2001:in `block in run'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/usr/lib/ruby/gems/1.9.1/gems/rake-0.8.7/bin/rake:31:in `<top (required)>'
/usr/bin/rake:19:in `load'
/usr/bin/rake:19:in `<main>'
confiz@confiz-desktop:~/mango_apps/rails_app_sms$ .
bash: .: filename argument required
.: usage: . filename [arguments]

我已经在我的 gemfile 中提到了 gem，并且已经执行了 bundle install。

我的 database.yml 文件已经有正确的适配器，即适配器：mysql2

请帮我解决这个问题。

【问题讨论】：

安装 gem 时是否有任何错误信息？
感谢 sosborn 的及时回复。不，没有错误消息。使用此命令 gem install mysql2 --version=0.2.7 顺利安装
不确定您使用的是什么平台，但这个问题有很多答案可能会为您指明正确的方向：stackoverflow.com/questions/3467054/…
我在 linux (ubuntu 10.10) ruby 1.9.2p180 (2011-02-18 revision 30909) [i686-linux] Rails 3.0.6
PS：我已经看过并尝试了您提到的链接上的所有内容:(

标签： ruby-on-rails ruby mysql2

【解决方案1】：

如果我在 Gemfile 中使用 mysql2 v 0.2.19b4，我会发现同样的问题。如果我使用最新的 mysql2，这与由 Hobo（生成我的 Gemfile）规定的 rails 3.0.17 冲突。我从中得到的警告是：

This version of mysql2 (0.3.11) doesn't ship with the ActiveRecord adapter bundled anymore as it's now part of Rails 3.1. Please use the 0.2.x releases if you plan on using it in Rails <= 3.0.x

回到mysql2 v 0.2.x 最初的加载错误是因为rails mysql_adapter 调用require 'mysql' 而不是require 'mysql2'。

解决方案是在 Gemfile 中使用 gem 'mysql' 而不是 gem 'mysql2'

在我的情况下，捆绑器用户 gem mysql v 2.8.1 一切正常。

【讨论】：