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

ruby-on-rails ruby-on-rails-4 ruby-on-rails-4.1 mysql2 ruby-on-rails-4.2
newUserNameHere picture newUserNameHere · Sep 8, 2015 · Viewed 67.8k times · Source

In my gemfile I have:

gem 'mysql2'

My database.yml is as follows:

default: &default
  adapter: mysql2
  database: <%= ENV['db_name'] %>
  username: <%= ENV['db_user'] %>
  password: <%= ENV['db_pass'] %>
  host:     <%= ENV['db_host'] %>
  pool: 32
  socket:   <%= ENV['socket'] %>

development:
  <<: *default

production:
  <<: *default

I've run both bundle update and bundle install and my Gemfile.lock shows mysql2.

However when I run rake db:migrate I get this on both my computer and on the staging server:

myproject.com(master)$ rake db:migrate
WARNING: Use strings for Figaro configuration. 10000012508 was converted to "10000012508".
WARNING: Use strings for Figaro configuration. 860526407370038 was converted to "860526407370038".
rake aborted!
Gem::LoadError: Specified 'mysql2' for database adapter, but the gem is not loaded. Add `gem 'mysql2'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).
.....

Just to make sure there wasn't a bad version of mysql2 or something, I did bundle clean --force and ran bundle install and bundle update again and when I run gem list I see mysql2 (0.4.0) and no other versions.

Any ideas would be most appreciated.

SOLUTION

It's currently an issue with Rails 4.1.x and 4.2.x, per this bug report, it will be fixed in the next release of rails 4.2.x (credit to dcorr in comments for the link).

In the mean time you can fix by doing downgraded to version 0.3.18 of mysql2 by adding this line to your gemfile:

gem 'mysql2', '~> 0.3.18'

Answer

Kaleem Ullah picture Kaleem Ullah · Sep 16, 2015

Just do:

gem 'mysql2', '~> 0.3.18' this gem works with rails version 4.x.x

if install gem 'mysql2', '~> 0.4.0' it produces gem load error and causes compatibility issues

Related questions

In Rails 4.1, how to find records by enum symbol?

Assume I have this model: class Conversation < ActiveRecord::Base enum status: [ :active, :archived ] end How can I find all active conversations without using the numeric value of the enum or without having to iterate over each conversation? I tried …

Read More
Undefined method attr_accessible error for User

I'm trying to create a login of sorts. I created a User scaffold and have this code in my user.rb class User < ActiveRecord::Base attr_accessible :name, :password_digest, :password, :password_confirmation has_secure_password end I keep …

Read More
Negate ActiveRecord query scope

I have a slightly complicated scope on a model class Contact < ActiveRecord::Base scope :active, -> { where(inactive: false) } scope :groups, -> { where(contact_type: 2308) } scope :group_search, -> (query) do active.groups.where("last_name …

Read More