Error When Changing to MySQL2 on Heroku

Question

For my Heroku app (Rails 3.1.4 and Ruby 1.9.2), I'm trying to change to a database that is using MySQL2, but I'm receiving an error from Heroku (which is crashing my app):

3.1.4/lib/active_record/connection_adapters/abstract/connection_specification.rb:71:in `rescue in establish_connection': Please install the mysql12 adapter: `gem install activerecord-mysql12-adapter` (no such file to load -- active_record/connection_adapters/mysql12_adapter) (RuntimeError) EXCEPT

In my gemfile, I have:

group :production do
  gem "mysql2", "~> 0.3.11"
end

group :development, :test do
  gem 'mysql', '2.8.1'
end

In my database.yml, I have:

development:
  adapter: mysql

production:
  adapter: mysql2

Here's what I've tried unsuccessfully(all attempts installed correctly locally and in Heroku):

1. Per this answer, I tried (in my gemfile), mysql2 version "< 0.3"

2. Per another answer for that question, I tried '< 0.3.7' which didn't work

3. I tried gem "mysql2", "~> 0.3.11" per this answer, but it didn't work

4. Per the gem's site, I tried (in my gemfile), mysql2 version "~> 0.2.7" and it installed mysql2 0.2.18 (successfully locally and in Heroku)

Answer 1

I'm sure you've figured this out or moved on long ago, but I was running into the same issue and thought I'd share what worked for me for anyone else who comes along.

In addition to what you mention above, if you're using Heroku you also have to specify mysql2:// in the DATABASE_URL instead of mysql://. See the ClearDB writeup here: https://devcenter.heroku.com/articles/cleardb

And update their instructions to use mysql2:// instead of mysql:// like so:

heroku config:add DATABASE_URL='mysql2://adffdadf2341:[email protected]/heroku_db?reconnect=true'

Hope that helps.