ActiveRecord::Schema

Active Record Schema

Allows programmers to programmatically define a schema in a portable DSL. This means you can define tables, indexes, etc. without using SQL directly, so your applications can more easily support multiple databases.

Usage:

ActiveRecord::Schema.define do
  create_table :authors do |t|
    t.string :name, null: false
  end

  add_index :authors, :name, :unique

  create_table :posts do |t|
    t.integer :author_id, null: false
    t.string :subject
    t.text :body
    t.boolean :private, default: false
  end

  add_index :posts, :author_id
end

ActiveRecord::Schema is only supported by database adapters that also support migrations, the two features being very similar.

Methods
D
Class Public methods
define(info = {}, &block)

Eval the given block. All methods available to the current connection adapter are available within the block, so you can easily use the database definition DSL to build up your schema ( create_table, add_index, etc.).

The info hash is optional, and if given is used to define metadata about the current schema (currently, only the schema's version):

ActiveRecord::Schema.define(version: 20380119000001) do
  ...
end

Source: show | on GitHub 

# File activerecord/lib/active_record/schema.rb, line 43
def self.define(info = {}, &block)
  new.define(info, &block)
end