# Uninitialized constant MysqlCompat::MysqlRes

**URL:** <https://www.ruby-forum.com/t/uninitialized-constant-mysqlcompat-mysqlres/186217>\
**Category:** Rails\
**Created:** [April 2, 2010, 11:35am UTC](https://www.ruby-forum.com/t/uninitialized-constant-mysqlcompat-mysqlres/186217 "2010-04-02T11:35:05Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Garfield.Yu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/e47774/32.png) [@Garfield.Yu](https://www.ruby-forum.com/u/Garfield.Yu)\
**Post date:** [April 2, 2010, 11:35am UTC](https://www.ruby-forum.com/t/uninitialized-constant-mysqlcompat-mysqlres/186217/1 "2010-04-02T11:35:05Z")

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Macbook 466  
Mac OS X 10.6.3  
Rails 2.3.5  
Ruby 1.8.7  
MySQL mysql-5.1.45-osx10.6-x86

after install mysql gem with “sudo env ARCHFLAGS=”-arch i386" gem  
install mysql – --with-mysql-config=/usr/local/mysql/bin/mysql\_config  
"

use “rake db:migrate”

but always dispay the error msg:

rake aborted!  
uninitialized constant MysqlCompat::MysqlRes

what should I do?

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<div class="post-metadata">

**Author:** ![Garfield.Yu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/e47774/32.png) [@Garfield.Yu](https://www.ruby-forum.com/u/Garfield.Yu)\
**Post date:** [April 3, 2010, 11:57am UTC](https://www.ruby-forum.com/t/uninitialized-constant-mysqlcompat-mysqlres/186217/2 "2010-04-03T11:57:00Z")

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> rake aborted!  
> uninitialized constant MysqlCompat::MysqlRes
> 
> what should I do?

Few things to check:

- Is the config file location you’ve given correct?
- Have you checked your mysql logs for errors?
- Looks like you might be using homebrew; I had an issue where I had a  
another mysql config file (from a previous installation) /etc/my.cnf  
which was being read before the mysql\_config file - if so remove the  
my.cnf file.
- Are you running the correct version i.e. maybe you need to install the  
mysql gem with -arch x86\_64 instead.

Cheers  
Luke