method

change_table

v7.1.3.4 - Show latest stable - 1 note - Class: ActiveRecord::ConnectionAdapters::SchemaStatements

change_table(table_name, base = self, **options) public

A block for changing columns in table.

# change_table() yields a Table instance
change_table(:suppliers) do |t|
  t.column :name, :string, limit: 60
  # Other column alterations here
end

The options hash can include the following keys:

:bulk

Set this to true to make this a bulk alter query, such as

ALTER TABLE `users` ADD COLUMN age INT, ADD COLUMN birthdate DATETIME ...

Defaults to false.

Only supported on the MySQL and PostgreSQL adapter, ignored elsewhere.

Add a column

change_table(:suppliers) do |t|
  t.column :name, :string, limit: 60
end

Change type of a column

change_table(:suppliers) do |t|
  t.change :metadata, :json
end

Add 2 integer columns

change_table(:suppliers) do |t|
  t.integer :width, :height, null: false, default: 0
end

Add created_at/updated_at columns

change_table(:suppliers) do |t|
  t.timestamps
end

Add a foreign key column

change_table(:suppliers) do |t|
  t.references :company
end

Creates a company_id(bigint) column.

Add a polymorphic foreign key column

change_table(:suppliers) do |t|
  t.belongs_to :company, polymorphic: true
end

Creates company_type(varchar) and company_id(bigint) columns.

Remove a column

change_table(:suppliers) do |t|
  t.remove :company
end

Remove several columns

change_table(:suppliers) do |t|
  t.remove :company_id
  t.remove :width, :height
end

Remove an index

change_table(:suppliers) do |t|
  t.remove_index :company_id
end

See also Table for details on all of the various column transformations.

Show source

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 496
      def change_table(table_name, base = self, **options)
        if supports_bulk_alter? && options[:bulk]
          recorder = ActiveRecord::Migration::CommandRecorder.new(self)
          yield update_table_definition(table_name, recorder)
          bulk_change_table(table_name, recorder.commands)
        else
          yield update_table_definition(table_name, base)
        end
      end

September 25, 2008

18 thanks

All methods

change_table :table do |t|

  t.column # adds an ordinary column. Ex: t.column(:name, :string)
  t.index # adds a new index.
  t.timestamps
  t.change # changes the column definition. Ex: t.change(:name, :string, :limit => 80)
  t.change_default # changes the column default value.
  t.rename # changes the name of the column.
  t.references
  t.belongs_to
  t.string
  t.text
  t.integer
  t.float
  t.decimal
  t.datetime
  t.timestamp
  t.time
  t.date
  t.binary
  t.boolean
  t.remove
  t.remove_references
  t.remove_belongs_to
  t.remove_index
  t.remove_timestamps
end