diff options
Diffstat (limited to 'guides/source/migrations.textile')
| -rw-r--r-- | guides/source/migrations.textile | 46 |
1 files changed, 24 insertions, 22 deletions
diff --git a/guides/source/migrations.textile b/guides/source/migrations.textile index c11f8e221b..52dba76e68 100644 --- a/guides/source/migrations.textile +++ b/guides/source/migrations.textile @@ -51,7 +51,7 @@ end This migration adds a table called +products+ with a string column called +name+ and a text column called +description+. A primary key column called +id+ will -also be added, however since this is the default we do not need to ask for this. +also be added, however since this is the default we do not need to explicitly specify it. The timestamp columns +created_at+ and +updated_at+ which Active Record populates automatically will also be added. Reversing this migration is as simple as dropping the table. @@ -65,7 +65,7 @@ class AddReceiveNewsletterToUsers < ActiveRecord::Migration change_table :users do |t| t.boolean :receive_newsletter, :default => false end - User.update_all ["receive_newsletter = ?", true] + User.update_all :receive_newsletter => true end def down @@ -82,6 +82,8 @@ it to default to +false+ for new users, but existing users are considered to have already opted in, so we use the User model to set the flag to +true+ for existing users. +h4. Using the change method + Rails 3.1 makes migrations smarter by providing a new <tt>change</tt> method. This method is preferred for writing constructive migrations (adding columns or tables). The migration knows how to migrate your database and reverse it when @@ -475,7 +477,16 @@ end </ruby> will add an +attachment_id+ column and a string +attachment_type+ column with -a default value of 'Photo'. +a default value of 'Photo'. +references+ also allows you to define an +index directly, instead of using +add_index+ after the +create_table+ call: + +<ruby> +create_table :products do |t| + t.references :category, :index => true +end +</ruby> + +will create an index identical to calling `add_index :products, :category_id`. NOTE: The +references+ helper does not actually create foreign key constraints for you. You will need to use +execute+ or a plugin that adds "foreign key @@ -497,7 +508,7 @@ and h4. Using the +change+ Method The +change+ method removes the need to write both +up+ and +down+ methods in -those cases that Rails know how to revert the changes automatically. Currently, +those cases that Rails knows how to revert the changes automatically. Currently, the +change+ method supports only these migration definitions: * +add_column+ @@ -635,10 +646,9 @@ example, $ rake db:migrate:up VERSION=20080906120000 </shell> -will run the +up+ method from the 20080906120000 migration. These tasks still -check whether the migration has already run, so for example +db:migrate:up -VERSION=20080906120000+ will do nothing if Active Record believes that -20080906120000 has already been run. +will run the +up+ method from the 20080906120000 migration. This task will first +check whether the migration is already performed and will do nothing if Active Record believes +that it has already been run. h4. Changing the output of running migrations @@ -727,9 +737,7 @@ column. class AddFlagToProduct < ActiveRecord::Migration def change add_column :products, :flag, :boolean - Product.all.each do |product| - product.update_attributes!(:flag => 'false') - end + Product.update_all :flag => false end end </ruby> @@ -752,9 +760,7 @@ column. class AddFuzzToProduct < ActiveRecord::Migration def change add_column :products, :fuzz, :string - Product.all.each do |product| - product.update_attributes! :fuzz => 'fuzzy' - end + Product.update_all :fuzz => 'fuzzy' end end </ruby> @@ -771,7 +777,7 @@ Both migrations work for Alice. Bob comes back from vacation and: -# Updates the source - which contains both migrations and the latests version of +# Updates the source - which contains both migrations and the latest version of the Product model. # Runs outstanding migrations with +rake db:migrate+, which includes the one that updates the +Product+ model. @@ -804,11 +810,9 @@ class AddFlagToProduct < ActiveRecord::Migration end def change - add_column :products, :flag, :integer + add_column :products, :flag, :boolean Product.reset_column_information - Product.all.each do |product| - product.update_attributes!(:flag => false) - end + Product.update_all :flag => false end end </ruby> @@ -823,9 +827,7 @@ class AddFuzzToProduct < ActiveRecord::Migration def change add_column :products, :fuzz, :string Product.reset_column_information - Product.all.each do |product| - product.update_attributes!(:fuzz => 'fuzzy') - end + Product.update_all :fuzz => 'fuzzy' end end </ruby> |