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Raking MySQL Over Rails

  • December 19, 2007
  • By W. Jason Gilmore
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Next, create the states.csv file, and store it within the newly created db/seed directory. A shortened version of the file is presented here:

id, name, abbreviation
1, Alabama, AL
2, Alaska, AK
3, Arizona, AZ
4, Arkansas, AR
5, California, CA
6, Colorado, CO

Next, you'll need to create a Rake file. The process and syntax behind doing so is worthy of an article unto itself, so just trust me on this. I'd been using a homebrewed task for some time, but recently came across a much more succinct solution created by Jeffrey Alan Hardy, which I've slightly modified to account for my preferred use of comma-separated seed files. Paste the following code into a file named seeder.task and save it to your Rails project's lib/tasks directory:

namespace :db do
   desc "Load seed fixtures (from db/seed) into the current
         environment's database."
   task :seed => :environment do
      require 'active_record/fixtures'
      Dir.glob(RAILS_ROOT + '/db/fixtures/*.csv').each do |file|
         Fixtures.create_fixtures('db/seed',
                                  File.basename(file, '.*'))
      end
   end
end

To populate the states table, execute the following command from within your project directory:

%>rake db:seeder

Check the states table, and you'll see it's been populated!

Migrating Data Between Databases

Ask five developers what the superior database solution is, and you're sure to get five different answers. Like the endless vi/emacs and Linux/Windows arguments, there's never a shortage of opinion when it comes to database adoption. However, reality occasionally can take precedence over preference, and you may find yourself in a position where the client has decided to make a last minute switch to MySQL after you've been developing the application for weeks using PostgreSQL. Due to a variety of inconsistencies among various database solutions, it just isn't as easy to migrate data as one might think.

Noted Rails developer Tobias Lütke encountered a similar problem, and created a great Rake task for dumping database data into YAML format, and repopulating any database supported by Rails Migrations (at the time of writing, MySQL, PostgreSQL, SQLite, SQL Server, Sybase, and Oracle). I won't reproduce the task here because it's rather lengthy. Instead, download it from here and place it into your project's lib/tasks directory.

Next, run the following Rake command to retrieve the data in YAML format.

%>rake db:backup:write

All of the tables found in the current environment's database have been backed up to db/backup! Now, all you need to do is update your database.yml file to point to your new database solution, and then execute the following command to populate the new database:

%>rake db:backup:write

Keep in mind that anything found in that new database will be deleted before the new data is populated!

Conclusion

Rake is an amazing tool capable of doing so much more than what was demonstrated in this tutorial. Be sure to check out the Rake homepage, and this great tutorial for more information about this powerful tool.

About the Author

W. Jason Gilmore is co-founder of IT Enlightenment. He's the author of several books, including the best-selling "Beginning PHP and MySQL 5: Novice to Professional, Second Edition" (Apress, 2006. 913pp.). Jason loves receiving email, so don't hesitate to write him at wjATwjgilmore.com.





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