/**
  * Perform search 
  */
 protected function performSearch()
 {
     include_once './Services/Search/classes/Lucene/class.ilLuceneSearcher.php';
     include_once './Services/Search/classes/Lucene/class.ilLuceneQueryParser.php';
     $qp = new ilLuceneQueryParser($this->search_cache->getQuery());
     $qp->parse();
     $searcher = ilLuceneSearcher::getInstance($qp);
     $searcher->setType(ilLuceneSearcher::TYPE_USER);
     $searcher->search();
     $this->showSearchForm();
     include_once './Services/Search/classes/class.ilRepositoryUserResultTableGUI.php';
     $user_table = new ilRepositoryUserResultTableGUI($this, 'performSearch', false, ilRepositoryUserResultTableGUI::TYPE_GLOBAL_SEARCH);
     $user_table->setLuceneResult($searcher->getResult());
     $user_table->parseUserIds($searcher->getResult()->getCandidates());
     $GLOBALS['tpl']->setVariable('SEARCH_RESULTS', $user_table->getHTML());
     return true;
 }