Use the freeResult DAO method

bin/cli.class.php

@@ -432,11 +432,7 @@ class civicrm_cli_csv_file extends civicrm_cli {
       $this->row++;
       if ($this->row % 1000 == 0) {
         // Reset PEAR_DB_DATAOBJECT cache to prevent memory leak
-        $GLOBALS['_DB_DATAOBJECT']['RESULTS'] = array();
-        $GLOBALS['_DB_DATAOBJECT']['RESULTSEQ'] = 1;
-        $GLOBALS['_DB_DATAOBJECT']['RESULTFIELDS'] = array();
-        // Forces garbage collection
-        memory_get_usage(TRUE);
+        CRM_Core_DAO::freeResult();
       }
       $params = $this->convertLine($data);
       $this->processLine($params);