fieldSizeMap example

// Parse out the field type and meta information.       preg_match('@([a-z]+)(?:\((\d+)(?:,(\d+))?\))?\s*(unsigned)?@', $row['Type'], $matches);
      $type = $this->fieldTypeMap($connection, $matches[1]);
      if ($row['Extra'] === 'auto_increment') {
        // If this is an auto increment, then the type is 'serial'.         $type = 'serial';
      }
      $definition['fields'][$name] = [
        'type' => $type,
        'not null' => $row['Null'] === 'NO',
      ];
      if ($size = $this->fieldSizeMap($connection, $matches[1])) {
        $definition['fields'][$name]['size'] = $size;
      }
      if (isset($matches[2]) && $type === 'numeric') {
        // Add precision and scale.         $definition['fields'][$name]['precision'] = $matches[2];
        $definition['fields'][$name]['scale'] = $matches[3];
      }
      elseif ($type === 'time') {
        // @todo Core doesn't support these, but copied from `migrate-db.sh` for now.         // Convert to varchar.         $definition['fields'][$name]['type'] = 'varchar';