class ActiveRecord::ConnectionAdapters::TableDefinition

end
t.references :taggable, polymorphic: { default: 'Photo' }, index: false
t.references :tagger, polymorphic: true
t.references :tag, index: { name: 'index_taggings_on_tag_id' }
create_table :taggings do |t|

Can also be written as follows using references:

add_index :taggings, [:tagger_id, :tagger_type]
add_index :taggings, :tag_id, name: 'index_taggings_on_tag_id'
end
t.string :taggable_type, default: 'Photo'
t.string :tagger_type
t.integer :tag_id, :tagger_id, :taggable_id
create_table :taggings do |t|

So what can be written like this:
will also create an index, similar to calling {add_index}[rdoc-ref:ConnectionAdapters::SchemaStatements#add_index].
options, these will be used when creating the _type column. The :index option
column if the :polymorphic option is supplied. If :polymorphic is a hash of
TableDefinition#references will add an appropriately-named _id column, plus a corresponding _type

TableDefinition#timestamps that'll add +created_at+ and +updated_at+ as datetimes.
There's a short-hand method for each of the type values declared at the top. And then there's

end
t.timestamps null: false
t.string :name, :value, default: "Untitled"
t.string :item_number, index: true
t.integer :shop_id, :creator_id
create_table :products do |t|

can also be written as follows using the short-hand:

add_index :products, :item_number
end
t.column :updated_at, :datetime
t.column :created_at, :datetime
t.column :value, :string, default: "Untitled"
t.column :name, :string, default: "Untitled"
t.column :item_number, :string
t.column :creator_id, :integer
t.column :shop_id, :integer
create_table :products do |t|

What can be written like this with the regular calls to column:

in a single statement.
They use the type as the method name instead of as a parameter and allow for multiple columns to be defined
Instead of calling #column directly, you can also work with the short-hand definitions for the default types.

== Short-hand examples

td.column(:granted, :boolean, index: true)
# Assuming +td+ is an instance of TableDefinition

== Examples

This method returns self.

Create an index for the column. Can be either true or an options hash.
* :index -
Additional options are:

for available options.
See {connection.add_column}[rdoc-ref:ConnectionAdapters::SchemaStatements#add_column]
Instantiates a new column for the table.

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