rename_column :table, :old_column, :new_column
You'll probably want to create a separate migration to do this. (Rename FixColumnName
as you will.):
script/generate migration FixColumnName
# creates db/migrate/xxxxxxxxxx_fix_column_name.rb
Then edit the migration to do your will:
# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
def self.up
rename_column :table_name, :old_column, :new_column
end
def self.down
# rename back if you need or do something else or do nothing
end
end
For Rails 3.1 use:
While, the up
and down
methods still apply, Rails 3.1 receives a change
method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".
See "Active Record Migrations" for more information.
rails g migration FixColumnName
class FixColumnName < ActiveRecord::Migration
def change
rename_column :table_name, :old_column, :new_column
end
end
If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:
rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...
You could use change_table
to keep things a little neater:
class FixColumnNames < ActiveRecord::Migration
def change
change_table :table_name do |t|
t.rename :old_column1, :new_column1
t.rename :old_column2, :new_column2
...
end
end
end
Then just db:migrate
as usual or however you go about your business.
For Rails 4:
While creating a Migration
for renaming a column, Rails 4 generates a change
method instead of up
and down
as mentioned in the above section. The generated change
method is:
$ > rails g migration ChangeColumnName
which will create a migration file similar to:
class ChangeColumnName < ActiveRecord::Migration
def change
rename_column :table_name, :old_column, :new_column
end
end
Are you using Heroku?
Heroku will inject plugins in Rails 3.x applications ..
To avoid this
injection in Rails 3, include the rails_12factor gem in your
application. (Heroku Ruby Support 2013-10-26)
The rails_12factor gem is also required in rails 4.
If this gem is not present in your application, you will receive a
warning while deploying, and your assets and logs will not be
functional. (Rails 4 on Heroku 2013-10-26)
As recently as 2013-08, heroku always injected plugins in rails 3 apps, even apps with the recommended gems. This was an issue with the ruby buildpack, and was fixed by PR 11, merged on 2013-08-06.
Best Answer
I just wrote a blog post on this: How to Convert Simple Rails 2.3 Style Plugins for Rails 3.2