How can I rename a database column in a Ruby on Rails migration?
I wrongly named a column hased_password instead of hashed_password .
How do I update the database schema, using migration to rename this column?
rename_column :table, :old_column, :new_column
Update:
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
An update for Rails 3.1
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"
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
Thank you, Luke && Turadg , for bringing up the topic.
Then just db:migrate as usual or however you go about your business.
An update for Rails 4
While creating a Migration as for renaming a column, Rails 4 generates a change method instead of up and down as mentioned in the above answer. The generated change method is as below :
$ > rails g migration ChangeColumnName
which will create a migration file similar to this :
class ChangeColumnName < ActiveRecord::Migration
def change
rename_column :table_name, :old_column, :new_column
end
end
IMO, in this case, better use rake db:rollback . Then edit your migration and again type rake db:migrate . However, if you have data in the column you don't want to lose, then use rename_column .
http://api.rubyonrails.org/classes/ActiveRecord/Migration.html
Under Available Transformations
rename_column(table_name, column_name, new_column_name):
Renames a column but keeps the type and content.
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