Rails: Specified 'Mysql2' for Database Adapter But the Gem Is Not Loaded

Rails 4 - Gem::LoadError: Specified 'mysql2' for database adapter, but the gem is not loaded

Just a further update - the solution in the question is correct.

The 4th comment is worth taking note of:

This isn't a bug with mysql2, it's a problem with the requirement in
the ActiveRecord adapter: http://github.com/rails/rails/issues/21544.
This is fixed in rails master:
https://github.com/rails/rails/commit/5da5e3772c32593ecf2f27b8865e81dcbe3af692

I was able to tie Rails 4.2.4 to the 4-2-stable branch and get it working with the latest mysql2:

gem 'rails', '~> 4.2.4', git: "git://github.com/rails/rails.git", branch: '4-2-stable'
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw] #-> Rails 4.1+

#DB
gem 'mysql2'

Rails: Specified 'mysql2' for database adapter but the gem is not loaded

Add the following to your Gemfile:

gem 'mysql2', '~> 0.3.18'

Then run:

bundle install

Gem::LoadError Specified 'mysql2' for database adapter, but the gem is not loaded

It doesn't load mysql2 gem because new version of mysql2(0.4.1) gem unable to load the mysql2_adaptor. This is working for me.

gem 'mysql2', '~> 0.3.13'

and run

bundle install

If still facing problem then This solution will surely help

Note: I'm assuming that you've mysql database installed on your system :P

Add `gem 'mysql2'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord)

You started a string which you didn't end at the end of this line :

gem 'mysql2', '~> 0.3.20'"

Change it to this:

gem 'mysql2', '~> 0.3.20'

Gem::LoadError: Specified 'mysql' for database adapter, but the gem is not loaded

When you set your DATABASE_URL, you need to specify to use mysql2:// instead of mysql://

Something like this:

heroku config:set DATABASE_URL='mysql2://adffdadf2341:adf4234@us-cdbr-east.cleardb.com/heroku_db?reconnect=true'

Specified sqlite3 for database adapter but gem is not loaded

Your sqlite3 gem is not being loaded, because of where you've got it in the Gemfile. Take it out of platform :ruby do and place it outside of that block , May be right under gem 'rails', '~> 4.2.0'

Same source code on two machines yield different executable behavior

The app uses the Regional Settings of the machine it's running on, and it looks like it is your problem. You can force a thread to use a specific culture by setting System.Threading.Thread.CurrentThread.CurrentCulture and System.Threading.Thread.CurrentThread.CurrentUICulture to a specific value.

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