change_ids_from_integer_to_bigint.rb

class ChangeIdsFromIntegerToBigint < ActiveRecord::Migration[5.1]
  def up
    do_migrate :integer, :bigint
  end

  def down
    do_migrate :bigint, :integer
  end

  private

  def do_migrate(type_from, type_to)
    ApplicationRecord.connection.tables.each do |table|
      begin
        klass = table.classify.constantize
        klass.columns.each do |column|
          next unless column.name =~ /\Aid\z|_id\z/ && column.type == type_from
          puts "#{table}, #{column.name}, #{column.type}, #{column.default.inspect}, #{column.null}"
          change_column table, column.name, type_to, default: column.default, null: column.null
        end
      rescue NameError => e
        # ignore
      end
    end
  end
end