Rails Cannot Load Such File -- MySQL2/Mysql2 (Loaderror)

rake aborted! cannot load such file -- mysql2/mysql2 on El Capitan

This problem does ring a bell, but instead of digging out the Internet and my memory, I have just tried the following: Install the latest mysql2 of the 0.3 series (0.3.20 at time of writing), and bundle it up for the application.

The problem seems that the latest mysql2 gem version 0.4 is not compatible with Rails 3.

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Your gem versions cannot be changed, and you want to have the same versions as production. To do so, you could just copy over your Gemfile.lock file from the production server, put it in your local folder aside the Gemfile, and execute the bundle install command.

Note that if your Gemfile specifies:

gem 'mysql2', '> 0.3'

Then Bundler will install the latest version that matches 0.n where n >= 3. At time of writing, that leads Bundler to get a 0.4 version, which is not compatible with your Rails version (Bundler cannot infer that from your Gemfile). A workaround for you is to modify your copy of the Gemfile (and committing it to your project may be a good idea):

gem 'mysql2', '> 0.3.13'  # put here the actual version used in production

Doing so, Bundler will install a version matchings 0.3.n, with n >= 13.

Ruby on Rails - cannot load such file -- mysql2/2.2/mysql2 (LoadError)

The problem is that the mysql2 gem is not installing with its native dependencies. In previous versions of Ruby, this would have triggered the unable to build native gem extension error:

Something has changed in Ruby 2.2 so that you can install the gem without it building the native extension. This does not mean the problem is resolved however - and so you have to ensure you install the gem with the appropriate dependencies.

Tutorial:

1. Download C-Connector from MYSQL (note your version of Ruby -- if you're using 64 bit, download the 64 bit version)

2. Unzip / Install the MYSQL C-Connector folder onto your HDD (don't have any spaces in the path)

3. Run the following command: gem install mysql2 --platform=ruby -- '--with-mysql-dir="C:/your-mysql-connector-path"'

4. This should install the gem with the files it needs

5. Then you can copy libmysql.dll from C:/your-mysql-connector-path -> c:/your-ruby-install/bin`

The difference between this install and the previous one will be that this should mention that the native gem extensions are being installed (This could take a while), which suggests that Ruby is looking at the library.

This time, if it installs correctly, it should work for you.

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If you're still seeing an error, you'll have to uninstall any existing versions of the mysql2 gem on your system:

If you're getting an error, you just need to type gem uninstall mysql2, select all and then repeat the steps above.

cannot load such file -- mysql2/mysql2

I deleted my tmp/ folder and it's worked for me.

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