This was the one post I made on my tumblr blog. Since it looked kind of lonely up there I thought I would bring it over…

I had quite a bit of a headache trying to get the MySQL ruby gem working on Snow Leopard.  Every time I would try to migrate my database or start Mongrel I would get “NameError (uninitialized constant MysqlCompat::MysqlRes)”.

After doing some googling I found the ruby weblog guide for upgrading to Snow Leopard.  There they recommend installing the 64 bit version of MySQL and then to install the gem run the following command:

$ sudo env ARCHFLAGS="-arch x86_64" gem install mysql -- --with-mysql-config=/usr/local/mysql/bin/mysql_config

MySQL and the gem installed ok but I would still get the same error when trying to migrate or start the development server.  A little more googling led me to Robby Grossman’s blog with instructions for installing MySQL using macports and a slightly different command for installing the gem.
To install MySQL with macports:

$ sudo port install mysql5-devel
$ sudo /opt/local/lib/mysql5/mysql_install_db -user=mysql

Then I combined his instructions for installing the gem with the one on the ruby weblog.

$ sudo env ARCHFLAGS="-arch x86_64" gem install mysql -- --with-mysql-config=/usr/local/mysql/bin/mysql_config

Hope this helps, Good luck!