database_tasks.rb

# From activerecord/lib/active_record/tasks/database_tasks.rb ~line 199

# ...

      def load_seed
        if seed_loader
          ActiveRecord::Base.transaction do  # <- Wrapped seeder in a transaction block
            seed_loader.load_seed            #
          end                                #
        else
          raise "You tried to load seed data, but no seed loader is specified. Please specify seed " +
                "loader with ActiveRecord::Tasks::DatabaseTasks.seed_loader = your_seed_loader\n" +
                "Seed loader should respond to load_seed method"
        end
      end
      
# ...