Represents the schema of an SQL table in an abstract way. This class provides methods for manipulating the schema representation.
Inside migration files, the t
object in create_table is actually of this type:
class SomeMigration < ActiveRecord::Migration[7.0]
def up
create_table :foo do |t|
puts t.class # => "ActiveRecord::ConnectionAdapters::TableDefinition"
end
end
def down
...
end
end
- #
- B
- C
- F
- I
- N
- R
- T
Attributes
[R] | as | |
[R] | check_constraints | |
[R] | comment | |
[R] | foreign_keys | |
[R] | if_not_exists | |
[R] | indexes | |
[R] | name | |
[R] | options | |
[R] | temporary |
Class Public methods
new( conn, name, temporary: false, if_not_exists: false, options: nil, as: nil, comment: nil, ** ) Link
# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 306 def initialize( conn, name, temporary: false, if_not_exists: false, options: nil, as: nil, comment: nil, ** ) @conn = conn @columns_hash = {} @indexes = [] @foreign_keys = [] @primary_keys = nil @check_constraints = [] @temporary = temporary @if_not_exists = if_not_exists @options = options @as = as @name = name @comment = comment end
Instance Public methods
[](name) Link
Returns a ColumnDefinition for the column with name name
.
check_constraint(expression, **options) Link
column(name, type, index: nil, **options) Link
Instantiates a new column for the table. See connection.add_column for available options.
Additional options are:
-
:index
- Create an index for the column. Can be eithertrue
or an options hash.
This method returns self
.
Examples
# Assuming +td+ is an instance of TableDefinition
td.column(:granted, :boolean, index: true)
Short-hand examples
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 do |t|
t.column :shop_id, :integer
t.column :creator_id, :integer
t.column :item_number, :string
t.column :name, :string, default: "Untitled"
t.column :value, :string, default: "Untitled"
t.column :created_at, :datetime
t.column :updated_at, :datetime
end
add_index :products, :item_number
can also be written as follows using the short-hand:
create_table :products do |t|
t.integer :shop_id, :creator_id
t.string :item_number, index: true
t.string :name, :value, default: "Untitled"
t.timestamps null: false
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. The :index
option will also create an index, similar to calling add_index. 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
add_index :taggings, :tag_id, name: 'index_taggings_on_tag_id'
add_index :taggings, [:tagger_id, :tagger_type]
Can also be written as follows using references:
create_table :taggings do |t|
t.references :tag, index: { name: 'index_taggings_on_tag_id' }
t.references :tagger, polymorphic: true
t.references :taggable, polymorphic: { default: 'Photo' }, index: false
end
# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 410 def column(name, type, index: nil, **options) name = name.to_s type = type.to_sym if type if @columns_hash[name] if @columns_hash[name].primary_key? raise ArgumentError, "you can't redefine the primary key column '#{name}'. To define a custom primary key, pass { id: false } to create_table." else raise ArgumentError, "you can't define an already defined column '#{name}'." end end if @conn.supports_datetime_with_precision? if type == :datetime && !options.key?(:precision) options[:precision] = 6 end end @columns_hash[name] = new_column_definition(name, type, **options) if index index_options = index.is_a?(Hash) ? index : {} index(name, **index_options) end self end
columns() Link
Returns an array of ColumnDefinition objects for the columns of the table.
foreign_key(to_table, **options) Link
index(column_name, **options) Link
Adds index options to the indexes hash, keyed by column name This is primarily used to track indexes that need to be created after the table
index(:account_id, name: 'index_projects_on_account_id')
references(*args, **options) Link
Adds a reference.
t.references(:user)
t.belongs_to(:supplier, foreign_key: true)
t.belongs_to(:supplier, foreign_key: true, type: :integer)
See connection.add_reference for details of the options you can use.
remove_column(name) Link
remove the column name
from the table.
remove_column(:account_id)
timestamps(**options) Link
Appends :datetime
columns :created_at
and :updated_at
to the table. See connection.add_timestamps
t.timestamps null: false
# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 464 def timestamps(**options) options[:null] = false if options[:null].nil? if !options.key?(:precision) && @conn.supports_datetime_with_precision? options[:precision] = 6 end column(:created_at, :datetime, **options) column(:updated_at, :datetime, **options) end