$config = MediaWikiServices::getInstance()->getConfigFactory()->makeConfig( 'CirrusSearch' );
$conn = new Connection( $config );$searcher = new Searcher( $conn, 0, 0, $config, [], $wgUser );

$db = wfGetDB( DB_REPLICA );
$titles = $db->selectFieldValues( 'page', 'page_title' );

foreach ( $titles as $text ) {
	$title = Title::newFromDBkey( $text );

	$docId = $config->makeId( $title->getArticleID() );
	$esSources = $searcher->get( [ $docId ], true );
	if ( !$esSources->isOK() ) {
		echo $title->getText();
	}
}