diff --git a/src/acdhOeaw/arche/oaipmh/search/BaseSearch.php b/src/acdhOeaw/arche/oaipmh/search/BaseSearch.php
index aaad912..ce6b394 100644
--- a/src/acdhOeaw/arche/oaipmh/search/BaseSearch.php
+++ b/src/acdhOeaw/arche/oaipmh/search/BaseSearch.php
@@ -26,7 +26,6 @@
 
 namespace acdhOeaw\arche\oaipmh\search;
 
-use DateTime;
 use PDO;
 use Psr\Log\AbstractLogger;
 use zozlak\queryPart\QueryPart;
@@ -247,7 +246,7 @@ private function findQuery(string $id, string $from, string $until,
         $delDataQP     = $this->deleted->getDeletedData();
         $setDataQP     = $this->sets->getSetData();
         $query         = "
-            WITH valid AS (
+            WITH valid AS MATERIALIZED (
                 SELECT id
                 FROM
                     resources