Class | ActiveRecord::ConnectionAdapters::TableDefinition |
In: |
lib/active_record/connection_adapters/abstract/schema_definitions.rb
|
Parent: | Object |
Represents a SQL table in an abstract way. Columns are stored as a ColumnDefinition in the columns attribute.
columns | [RW] |
Instantiates a new column for the table. The type parameter is normally one of the migrations native types, which is one of the following: :primary_key, :string, :text, :integer, :float, :decimal, :datetime, :timestamp, :time, :date, :binary, :boolean.
You may use a type not in this list as long as it is supported by your database (for example, "polygon" in MySQL), but this will not be database agnostic and should usually be avoided.
Available options are (none of these exists by default):
Please be aware of different RDBMS implementations behavior with :decimal columns:
This method returns self.
# Assuming td is an instance of TableDefinition td.column(:granted, :boolean) # granted BOOLEAN td.column(:picture, :binary, :limit => 2.megabytes) # => picture BLOB(2097152) td.column(:sales_stage, :string, :limit => 20, :default => 'new', :null => false) # => sales_stage VARCHAR(20) DEFAULT 'new' NOT NULL td.column(:bill_gates_money, :decimal, :precision => 15, :scale => 2) # => bill_gates_money DECIMAL(15,2) td.column(:sensor_reading, :decimal, :precision => 30, :scale => 20) # => sensor_reading DECIMAL(30,20) # While <tt>:scale</tt> defaults to zero on most databases, it # probably wouldn't hurt to include it. td.column(:huge_integer, :decimal, :precision => 30) # => huge_integer DECIMAL(30)
Instead of calling column directly, you can also work with the short-hand definitions for the default types. They use the type as the method name instead of as a parameter and allow for multiple columns to be defined in a single statement.
What can be written like this with the regular calls to column:
create_table "products", :force => true do |t| t.column "shop_id", :integer t.column "creator_id", :integer t.column "name", :string, :default => "Untitled" t.column "value", :string, :default => "Untitled" t.column "created_at", :datetime t.column "updated_at", :datetime end
Can also be written as follows using the short-hand:
create_table :products do |t| t.integer :shop_id, :creator_id t.string :name, :value, :default => "Untitled" t.timestamps end
There‘s a short-hand method for each of the type values declared at the top. And then there‘s TableDefinition#timestamps that‘ll add created_at and updated_at as datetimes.
TableDefinition#references will add an appropriately-named _id column, plus a corresponding _type column if the :polymorphic option is supplied. If :polymorphic is a hash of options, these will be used when creating the _type column. So what can be written like this:
create_table :taggings do |t| t.integer :tag_id, :tagger_id, :taggable_id t.string :tagger_type t.string :taggable_type, :default => 'Photo' end
Can also be written as follows using references:
create_table :taggings do |t| t.references :tag t.references :tagger, :polymorphic => true t.references :taggable, :polymorphic => { :default => 'Photo' } end