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Diffstat (limited to 'guides/source/active_record_migrations.md')
| -rw-r--r-- | guides/source/active_record_migrations.md | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md index b8db21a989..de8bbc4174 100644 --- a/guides/source/active_record_migrations.md +++ b/guides/source/active_record_migrations.md @@ -241,7 +241,7 @@ generates ```ruby class AddUserRefToProducts < ActiveRecord::Migration def change - add_reference :products, :user, index: true + add_reference :products, :user, index: true, foreign_key: true end end ``` @@ -357,7 +357,7 @@ will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table ### Creating a Join Table -Migration method `create_join_table` creates a HABTM join table. A typical use +Migration method `create_join_table` creates an HABTM join table. A typical use would be: ```ruby @@ -425,7 +425,7 @@ change_column :products, :part_number, :text This changes the column `part_number` on products table to be a `:text` field. Besides `change_column`, the `change_column_null` and `change_column_default` -methods are used specifically to change the null and default values of a +methods are used specifically to change a not null constraint and default values of a column. ```ruby @@ -539,6 +539,14 @@ definitions: `change_table` is also reversible, as long as the block does not call `change`, `change_default` or `remove`. +`remove_column` is reversible if you supply the column type as the third +argument. Provide the original column options too, otherwise Rails can't +recreate the column exactly when rolling back: + +```ruby +remove_column :posts, :slug, :string, null: false, default: '', index: true +``` + If you're going to need to use any other methods, you should use `reversible` or write the `up` and `down` methods instead of using the `change` method. |