Migrates all your IDs to bigint. Useful when migrating from Rails < 5.1 to Rails 5.1+

all_to_bigint.rb

class AllToBigint < ActiveRecord::Migration[5.1]
  def up
    switch_all_to(__method__, :bigint)
  end

  def down
    switch_all_to(__method__, :integer)
  end

  private

  def switch_all_to(direction, new_type)
    remove_and_restore_fk direction: direction do
      # force require all models
      Rails.application.eager_load!

      index_by_table_name = ActiveRecord::Base.descendants.reject { |klass| klass.abstract_class || (klass.name.deconstantize == "MenuCir") }.index_by(&:table_name)

      index_by_table_name.each do |table_name, model|
        next if %w[schema_migrations ar_internal_metadata].include? table_name

        change_column table_name.to_sym, :id, new_type, auto_increment: true unless model.name.start_with?('HABTM')

        model.reflect_on_all_associations(:belongs_to).each do |association|
          if association.name == :left_side
            change_column table_name.to_sym, :"#{association.klass.name.demodulize.underscore}_id", new_type
          else
            change_column table_name.to_sym, :"#{association.name}_id", new_type
          end
        end
      end

      # friendly_id_slugs (if you use FriendlyID)
      change_column :friendly_id_slugs, :id, new_type, auto_increment: true
      change_column :friendly_id_slugs, :sluggable_id, new_type
    end
  end

  def remove_and_restore_fk(direction:)
    # Remove all FK to avoid having to deal with dependencies
    # remove all your foreign keys (manually)

    # omissis - I had to copy them from schema.rb. This is needed to avoid FK errors

    yield
    
    # omissis
    
    # add them again (manually)
  end
end