RuntimeError with mysql2 and rails3 (bundler)

问题:

I get this error

`establish_connection': Please install the mysql2 adapter: `gem install activerecord-mysql2-adapter` (no such file to load -- active_record/connection_adapters/mysql2_adapter) (RuntimeError)   from /opt/ruby-enterprise-1.8.7-2010.02/lib/ruby/gems/1.8/gems/activerecord- 

Here is dump of whole error and my config and gemfile.

回答1:

I had the same error after upgrading from Ubuntu 11.10 to 12.04. This is how I fixed the problem:

gem uninstall mysql2 bundle 

I think the key here is the 'native extensions' -- I suppose when I installed last, I was using a different version of mysql.

Installing mysql2 (0.3.11) with native extensions 

回答2:

I was getting the same error while using rails 3.0.7 and mysql2 0.3.2. The solution, which I found here, is to use an older version of mysql2. Thus edit your gemfile to

gem 'mysql2', '

and run

bundle install  

回答3:

Also need to change adapter from mysql to mysql2 in database.yml as said here Install mysql2 gem on Snow Leopard for Rails 3 with rvm

From:

development: adapter: mysql

To:

development: adapter: mysql2

回答4:

Did you include the mysql2 gem in your gemfile instead of the old mysql gem, and ran bundle install afterwards?

回答5:

If you're using rvm, and possibly added mysql2 outside of rvm, try these steps: Confirm that your Gemfile says:

gem 'mysql2' 

or for Rails2.x:

gem 'mysql2', '~> 0.2.11' 

then:

$ cd RAILS_ROOT $ gem uninstall mysql2  Select gem to uninstall:  1. mysql2-0.2.11  2. mysql2-0.3.6  3. All versions > 3 # select "All versions" $ rvm gemset install mysql2 $ bundle install 

Now rails should start properly.

回答6:

This also fixed the issue I had with:

Please install the mysql2 adapter: `gem install activerecord-mysql2-adapter` (no such file to load -- active_record/connection_adapters/mysql2_adapter) 

You actually need to run: gem install mysql2 and add the gem to your config.

回答7:

just run "gem install mysql" also add the same in gemfile and run bundle. worked

回答8:

If anybody still facing problem of installing mysql2 gem with rails 3 on Windows, then refer to the detailed steps of installation on -

http://rorguide.blogspot.com/2011/03/installing-mysql2-gem-on-ruby-192-and.html

回答9:

I'm a beginner at ruby, rails, and linux. So if this solution did not work, I hold no responsibility :)

Step 1:

sudo gem uninstall mysql2 

Step 2:

sudo gem install mysql -v 0.2.7 

Start webrick, if the same problem still appears reinstall rails.

This solution works for me.

回答10:

Same issue for me too. Upgraded to Rails 3.1.rc4 then downgraded to 3.0.3. Worked for me.

回答11:

as of 0.3.0, and ActiveRecord 3.1 - the ActiveRecord adapter has been pulled out of this gem and into ActiveRecord itself. If you need to use mysql2 with Rails versions 0.2.7" in your Gemfile

the missing file (no such file to load) can be found in the pre 0.3.0 versions of mysql2.

quoted from the documentation of mysql2

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