MySQL Gem failure: MysqlCompat::MysqlRes on Snow Leopard

I am trying to get the mysql gem to work ... and it just doesn't want to. Every time I do a rake db:migrate, I get

uninitialized constant MysqlCompat::MysqlRes

I've installed mysql from this disk image: mysql-5.5.9-osx10.6-x86_64.dmg

I've run the gem install with the infamous archflags setting:

sudo env ARCHFLAGS="-arch x86_64" gem install --no-rdoc --no-ri mysql -- --with-mysql-config=/usr/local/mysql/bin/mysql_config

And the ruby version I'm using is the default from Snow Leopard:

[~/sites/testdb]$ file `which mysql`
/usr/local/mysql/bin/mysql: Mach-O 64-bit executable x86_64
[~/sites/testdb]$ file `which ruby`
/usr/bin/ruby: Mach-O universal binary with 3 architectures
/usr/bin/ruby (for architecture x86_64):    Mach-O 64-bit executable x86_64
/usr/bin/ruby (for architecture i386):  Mach-O executable i386
/usr/bin/ruby (for architecture ppc7400):   Mach-O executable ppc

My database.yml is pretty simple:

development:
  adapter: mysql
  host: 127.0.0.1
 开发者_如何学编程 database: testdb
  username: root
  password: 

Any help would be appreciated.

You can easy fix your problem.

If you don't use rvm:

sudo install_name_tool -change libmysqlclient.16.dylib /usr/local/mysql/lib/libmysqlclient.16.dylib /Library/Ruby/Gems/1.8/gems/mysql-2.8.1/lib/mysql_api.bundleruby

If you use rvm:

install_name_tool -change libmysqlclient.16.dylib usr/local/mysql/lib/libmysqlclient.16.dylib [YOUR_GEMSET_PATH]/gems/mysql-2.8.1/lib/mysql_api.bundle

I blogged about this last week: MySQL 5.5 on Mac OS X.

My alternate solution to using install_name_tool is to set DYLD_LIBRARY_PATH in your shell startup files. The advantage to this you do it once, whereas if you use install_name_tool, you will repeat that every time to re-install or upgrade the gem.

The mysql2 gem will have the same problem with a slightly different error message. The problem is how the libmysqlclient library is built. It doesn't include a full path, so anything linking with it can't find it at runtime.

I ran into the same error. On my machine, though, the mysql gen was built when I still had mysql 5.1 on my machine. Now, after upgrading to MySQL 5.5, the dyld-file referred by the original build /usr/local/mysql/lib/libmysqlclient.16.dylib didn't exist any more and was replaced by a file /usr/local/mysql/lib/libmysqlclient.18.dylib.

Completely rebuilding the mysql gem fixed things, i.e.

gem uninstall mysql
gem install mysql

You could try using the mysql2 gem which may not suffer from the same problems.

I've found it's often a lot better to use ruby and mysql from MacPorts or brew to keep everything on the same page and not mess with the system Ruby.

OS X comes with a version of MySQL that may not match up with what you have installed, or perhaps the gem installer is confused about which config program to use. Make sure mysql_config is returning the correct path.