diff options
Diffstat (limited to 'guides/source/active_record_migrations.md')
| -rw-r--r-- | guides/source/active_record_migrations.md | 31 |
1 files changed, 17 insertions, 14 deletions
diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md index 4d195988f8..9398244ccf 100644 --- a/guides/source/active_record_migrations.md +++ b/guides/source/active_record_migrations.md @@ -126,7 +126,7 @@ generator to handle making it for you: $ rails generate migration AddPartNumberToProducts ``` -This will create an empty but appropriately named migration: +This will create an appropriately named empty migration: ```ruby class AddPartNumberToProducts < ActiveRecord::Migration[5.0] @@ -135,9 +135,14 @@ class AddPartNumberToProducts < ActiveRecord::Migration[5.0] end ``` -If the migration name is of the form "AddXXXToYYY" or "RemoveXXXFromYYY" and is -followed by a list of column names and types then a migration containing the -appropriate `add_column` and `remove_column` statements will be created. +This generator can do much more than append a timestamp to the file name. +Based on naming conventions and additional (optional) arguments it can +also start fleshing out the migration. + +If the migration name is of the form "AddColumnToTable" or +"RemoveColumnFromTable" and is followed by a list of column names and +types then a migration containing the appropriate `add_column` and +`remove_column` statements will be created. ```bash $ rails generate migration AddPartNumberToProducts part_number:string @@ -220,6 +225,8 @@ class CreateProducts < ActiveRecord::Migration[5.0] create_table :products do |t| t.string :name t.string :part_number + + t.timestamps end end end @@ -247,7 +254,7 @@ end ``` This migration will create a `user_id` column and appropriate index. -For more `add_reference` options, visit the [API documentation](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_reference). +For more `add_reference` options, visit the [API documentation](https://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_reference). There is also a generator which will produce join tables if `JoinTable` is part of the name: @@ -460,7 +467,6 @@ number of digits after the decimal point. * `default` Allows to set a default value on the column. Note that if you are using a dynamic value (such as a date), the default will only be calculated the first time (i.e. on the date the migration is applied). -* `index` Adds an index for the column. * `comment` Adds a comment for the column. Some adapters may support additional options; see the adapter specific API docs @@ -479,7 +485,7 @@ add_foreign_key :articles, :authors This adds a new foreign key to the `author_id` column of the `articles` table. The key references the `id` column of the `authors` table. If the -column names can not be derived from the table names, you can use the +column names cannot be derived from the table names, you can use the `:column` and `:primary_key` options. Rails will generate a name for every foreign key starting with @@ -491,9 +497,6 @@ NOTE: Active Record only supports single column foreign keys. `execute` and `structure.sql` are required to use composite foreign keys. See [Schema Dumping and You](#schema-dumping-and-you). -NOTE: The SQLite3 adapter doesn't support `add_foreign_key` since SQLite supports -only [a limited subset of ALTER TABLE](https://www.sqlite.org/lang_altertable.html). - Removing a foreign key is easy as well: ```ruby @@ -518,12 +521,12 @@ Product.connection.execute("UPDATE products SET price = 'free' WHERE 1=1") For more details and examples of individual methods, check the API documentation. In particular the documentation for -[`ActiveRecord::ConnectionAdapters::SchemaStatements`](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html) +[`ActiveRecord::ConnectionAdapters::SchemaStatements`](https://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html) (which provides the methods available in the `change`, `up` and `down` methods), -[`ActiveRecord::ConnectionAdapters::TableDefinition`](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html) +[`ActiveRecord::ConnectionAdapters::TableDefinition`](https://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html) (which provides the methods available on the object yielded by `create_table`) and -[`ActiveRecord::ConnectionAdapters::Table`](http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/Table.html) +[`ActiveRecord::ConnectionAdapters::Table`](https://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/Table.html) (which provides the methods available on the object yielded by `change_table`). ### Using the `change` Method @@ -946,7 +949,7 @@ If `:ruby` is selected, then the schema is stored in `db/schema.rb`. If you look at this file you'll find that it looks an awful lot like one very big migration: ```ruby -ActiveRecord::Schema.define(version: 20080906171750) do +ActiveRecord::Schema.define(version: 2008_09_06_171750) do create_table "authors", force: true do |t| t.string "name" t.datetime "created_at" |