Update BaseFieldDefinition with data migrate

/**
* Extend poll choices more than 255 characters.
*/
function poll_update_8006() {
 $connection = Database::getConnection();
 $entity_definition_update_manager = Drupal::entityDefinitionUpdateManager();
 $entity_type_id = 'poll_choice';
 // Check if we have updates for entity type.
 if ($entity_definition_update_manager->needsUpdates()) {
   $changes = $entity_definition_update_manager->getChangeSummary();
   if (array_key_exists($entity_type_id, $changes)) {
     // Set tables to update.
     $tables_to_update = [
       $entity_type_id . '_field_data',
     ];
     $tables_data = [];
     // Copy content from entity tables.
     foreach ($tables_to_update as $table_to_update) {
       $tables_data[$table_to_update] = $connection->select($table_to_update)
         ->fields($table_to_update)
         ->execute()->fetchAll();
       $connection->truncate($table_to_update)->execute();
     }
     // Apply updates.
     $entity_field_manager = \Drupal::service('entity_field.manager');
     $entity_field_manager->clearCachedFieldDefinitions();
     $storage_definitions = $entity_field_manager->getFieldStorageDefinitions($entity_type_id);
     if ($storage_definitions['choice']) {
       $entity_definition_update_manager->updateFieldStorageDefinition($storage_definitions['choice']);
     }
     // Insert content into updated entity tables.
     foreach ($tables_data as $table_name => $table_data) {
       foreach ($table_data as $result) {
         $data = (array) $result;
         // Save the information in the table.
         $connection->insert($table_name)
           ->fields($data)
           ->execute();
       }
     }
   }
 }
}