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PORolling back a failed Rails migration
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copied!<p>How do you roll back a failed rails migration? I would expect that <code>rake db:rollback</code> would undo the failed migration, but no, it rolls back the previous migration (the failed migration minus one). And <code>rake db:migrate:down VERSION=myfailedmigration</code> doesn't work either. I've ran into this a few times and it's very frustrating. Here's a simple test I made to duplicate the problem:</p> <pre><code>class SimpleTest < ActiveRecord::Migration def self.up add_column :assets, :test, :integer # the following syntax error will cause the migration to fail add_column :asset, :test2, :integer end def self.down remove_column :assets, :test remove_column :assets, :test2 end end </code></pre> <p>result:</p> <pre> == SimpleTest: migrating ===================================================== -- add_column(:assets, :test, :integer) -> 0.0932s -- add_column(:asset, :error) rake aborted! An error has occurred, all later migrations canceled: wrong number of arguments (2 for 3) </pre> <p>ok, lets roll it back:</p> <pre> $ rake db:rollback == AddLevelsToRoles: reverting =============================================== -- remove_column(:roles, :level) -> 0.0778s == AddLevelsToRoles: reverted (0.0779s) ====================================== </pre> <p>huh? that was my last migration before SimpleTest, not the failed migration. (And oh, it would be nice if the migration output included the version number.)</p> <p>So lets try running the down for the failed migration SimpleTest:</p> <pre> $ rake db:migrate:down VERSION=20090326173033 $ </pre> <p>Nothing happens, and no output either. But maybe it ran the migration anyway? So lets fix the syntax error in the SimpleTest migration, and try to run it again. </p> <pre> $ rake db:migrate:up VERSION=20090326173033 == SimpleTest: migrating ===================================================== -- add_column(:assets, :test, :integer) rake aborted! Mysql::Error: Duplicate column name 'test': ALTER TABLE `assets` ADD `test` int(11) </pre> <p>Nope. Obviously the migrate:down didn't work. It's not failing, it's just not executing.</p> <p>No way to get rid of that duplicate table other than manually going into the database and removing it, and then running the test. There's got to be a better way than that.</p>

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