How can I rename a database column in a Ruby on Rails migration?

alter-table, migration, rename, ruby-on-rails, ruby-on-rails-3

Solution

rename_column :table, :old_column, :new_column

You'll probably want to create a separate migration to do this. (Rename `FixColumnName` as you will.):

bin/rails 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

Problem

Original source