diff --git a/question/engine/datalib.php b/question/engine/datalib.php
index 0c0f2eb8494..a9063a4b491 100644
--- a/question/engine/datalib.php
+++ b/question/engine/datalib.php
@@ -768,22 +768,6 @@ ORDER BY
                 $qubaids->usage_id_in_params());
     }
 
-    /**
-     * This function is a work-around for poor MySQL performance with
-     * DELETE FROM x WHERE id IN (SELECT ...). We have to use a non-standard
-     * syntax to get good performance. See MDL-29520.
-     * @param string $test sql fragment.
-     * @param array $params used by $test.
-     */
-    protected function delete_attempt_steps_for_mysql($test, $params) {
-        // TODO once MDL-29589 is fixed, eliminate this method, and instead use the new $DB API.
-        $this->db->execute('
-                DELETE qas, qasd
-                  FROM {question_attempt_steps}     qas
-             LEFT JOIN {question_attempt_step_data} qasd ON qasd.attemptstepid = qas.id
-                 WHERE qas.questionattemptid ' . $test, $params);
-    }
-
     /**
      * Delete all the steps for a question attempt.
      * @param int $qaids question_attempt id.
@@ -795,19 +779,12 @@ ORDER BY
         }
         list($test, $params) = $this->db->get_in_or_equal($stepids, SQL_PARAMS_NAMED);
 
-        if ($deletefiles) {
-            $this->delete_response_files($context->id, $test, $params);
-        }
-
-        if ($this->db->get_dbfamily() == 'mysql') {
-            $this->delete_attempt_steps_for_mysql($test, $params);
-            return;
-        }
+        $this->delete_response_files($context->id, $test, $params);
 
         $this->db->delete_records_select('question_attempt_step_data',
                 "attemptstepid $test", $params);
         $this->db->delete_records_select('question_attempt_steps',
-                "attemptstepid $test", $params);
+                "id $test", $params);
     }
 
     /**