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：migrate
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中提到过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。
答案 0 :(得分：0)
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rails 3.0.17冲突，这是由Hobo（生成我的Gemfile）决定的。我得到的警告是：
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原来的加载错误是因为rails mysql_adapter调用require 'mysql'而不是require 'mysql2'。
解决方案是在Gemfile中使用gem 'mysql'而非gem 'mysql2'
在我的案例中，bundler用户使用gem mysql v 2.8.1，一切正常。