code: public function getSourceColumnNames(GetPropertyOptionsEvent $event)
      {
          if (($event->getEnvironment()->getDataDefinition()->getName() !== 'tl_metamodel_attribute')
              || ($event->getPropertyName() !== 'select_srcsorting')
          ) {
              return;
          }
  
          $model         = $event->getModel();
          $table         = $model->getProperty('tag_srctable');
          $schemaManager = $this->connection->getSchemaManager();
  
          if (!$table || !$schemaManager->tablesExist([$table])) {
              return;
          }
  
          $result = [];
  
          foreach ($schemaManager->listTableColumns($table) as $column) {
              $result[$column->getName()] = $column->getName();
          }
  
          $event->setOptions($result);
      }
docs: Retrieve all column names of type int for the current selected table.
  
  @param GetPropertyOptionsEvent $event The event.
  
  @return void