Nice tips about rails

Add a column in a migration and populate it immediately after.
reset_column_information

Example

	class AddNameToUser < ActiveRecord::Migration
  		def self.up
    		add_column :users, :name, :string
    		User.reset_column_information
    		User.find(:all).each do |user|
      			user.name = user.first_name + ' ' + user.last_name
    		end
    		remove_column :users, :first_name
    		remove_column :users, :last_name
		end
  	end

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