How to install MySQL Ruby gem in OS X Snow Leopard

I know this was posted multiple times by other people, but this information is scattered and hard to find so I’m posting quick summary.

First of all you must download MySQL binary. Be aware that ruby gem will not work with version newer than 5.1, and in Snow Leopard you should use 64-bit version.

After installing it (it should land in /usr/local) you can start compiling mysql gem. In order to do so you need to specify arch flags and path to your mysql dir:

env ARCHFLAGS="-arch i386" gem install mysql -- \
  --with-mysql-dir=/usr/local/mysql \
  --with-mysql-lib=/usr/local/mysql/lib \

Note that if you are using rvm then you shouldn’t install it in @global gemset - bundler will not see that and will try to recompile it again. So you will need to run this command for every gemset you will be using.