how bag's might work in migrations

gistfile1.rb

class SetupDatabase < ActiveRecord::Migration
  def self.up
    create_table :categories do |t|
      t.bag_for :category
      t.references :sector
      t.timestamps
    end
    add_bag_indexes_for(:categories)
  end
end

gistfile2.rb

module Bagman
  module TableBuilder
    def self.build_table(table, bag = nil)
      table.text :bag
      if bag
        bag.columns.select{|c| c.options[:index] }.each do |column|
          index_name = case column.options[:index]
                       when TrueClass
                        "index_#{column.name}"
                       else
                        options[:index]
                       end
          table.string index_name
        end
      end
    end

    def self.add_indexes(table, table_name, bag)
      bag.columns.select{|c| c.options[:index] }.each do |column|
        index_name = case column.options[:index]
                     when TrueClass
                      "index_#{column.name}"
                     else
                      options[:index]
                     end
        table.add_index(table_name, index_name)
      end
    end

  end
end

class ActiveRecord::ConnectionAdapters::TableDefinition
  def bag_for(klass_symbol)
    klass = klass_symbol.to_s.classify.constantize
    Bagman::TableBuilder.build_table(self, klass.bag)
  end
end

module ActiveRecord::ConnectionAdapters::SchemaStatements 
  def add_bag_indexes_for(table)
    klass = table.to_s.classify.constantize
    table_name = table.to_s.pluralize.to_sym
    Bagman::TableBuilder.add_indexes(self, table_name, klass.bag)
  end
end