mysql2 gem compiled for wrong mysql client library

Question

When try to connect to the mysql server through my rails application, I get the following error

D:/Program_Files/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require':  Incorrect MySQL client library version! This gem was compiled for 6.0.0 but the client library is 5.0.27. (RuntimeError) 

How can I rectify it?

Answer 1

Uninstalling and reinstalling the gem will often solve this issue with no need to download and move files around by hand. From your rails app directory:

> gem uninstall mysql2  You have requested to uninstall the gem:     mysql2-0.3.11 database_cleaner-0.9.1 depends on [mysql2 (>= 0)] If you remove this gems, one or more dependencies will not be met. Continue with Uninstall? [Yn]  Y Successfully uninstalled mysql2-0.3.11  > bundle install  Fetching gem metadata from http://rubygems.org/...... Fetching gem metadata from http://rubygems.org/.. Using rake (0.9.2) Using i18n (0.6.1) ... <SNIP> ... Installing mysql2 (0.3.11) with native extensions ... <SNIP> ... Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed. 

Answer 2

I had the same problem as you, or at least the symptom was the same.

Background: I was using Rails 3, the mysql2 gem, and MySQL community server version 5.5.21 (32-bit) installed locally on my Windows machine. I grabbed the client library (libmysql.dll) from the MySQL installation and copied it to my ruby installation's bin folder.

When I ran bundle exec rake db:create, I got the same error message as you and I thought "Hey, how can the client library be outdated when I got it from the latest MySQL release?"

There's a helpful message that is shown when you gem install mysql2. Unfortunately, if you install the gem with Bundler, Bundler eats the message. Here it is:

========================================================================= You've installed the binary version of mysql2. It was built using MySQL  Connector/C version 6.0.2. It's recommended to use the exact same version to avoid potential issues.  At the time of building this gem, the necessary DLL files where available in the following download:  http://dev.mysql.com/get/Downloads/Connector-C/mysql-connector-c-noinstall-6.0.2-win32.zip/from/pick  And put lib\libmysql.dll file in your Ruby bin directory, for example C:\Ruby\bin 

Following these instructions solved the problem for me.

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