/**
* Only reindex records for the given customer group ids.
*
* @param Mage_Index_Model_Event $event
* @return $this
*/
public function customerGroupSave(Mage_Index_Model_Event $event)
{
$limitToGroupIds = $event->getData('entity_ids');
$event->unsetData('entity_ids');
$this->_reindexEntity($event, $limitToGroupIds);
return $this;
}