Collection<String> (Project project) { CommonProcessors.CollectUniquesProcessor<String> processor = new CommonProcessors.CollectUniquesProcessor<>(); FileBasedIndex.getInstance().processAllKeys(KEY, processor, project); final Collection<String> results = new ArrayList<>(processor.getResults()); final GlobalSearchScope searchScope = GlobalSearchScope.projectScope(project); for (Iterator<String> iterator = results.iterator(); iterator.hasNext(); ) { final String id = iterator.next(); if (FileBasedIndex.getInstance().processValues(KEY, id, null, (file, value) -> false, searchScope)) { iterator.remove(); } } return results; }