private function getColumnTypes(): void
  {
    $rows = DataLayer::getAllTableColumns();
    foreach ($rows as $row)
    {
      $key = '@'.$row['table_name'].'.'.$row['column_name'].'%type@';
      $key = strtoupper($key);

      $value = $row['column_type'];
      if (isset($row['character_set_name'])) $value .= ' character set '.$row['character_set_name'];

      $this->replacePairs[$key] = $value;
    }

    $this->io->text(sprintf('Selected %d column types for substitution', sizeof($rows)));
  }