def clear
      flush
      with_tmpfile do |path, file|
        file.write(@format.header)
        file.close
        # Clear replaces the database file like a compactification does
        with_flock(File::LOCK_EX) do
          File.rename(path, @file)
        end
      end
      open
    end
def clear
      flush
      with_tmpfile do |path, file|
        file.write(@format.header)
        file.close
        # Clear replaces the database file like a compactification does
        with_flock(File::LOCK_EX) do
          File.rename(path, @file)
        end
      end
      open
    end
Clear the database log and yield