[MDL-31386] Correctly order answers in a lesson backup

mod/lesson/backup/moodle2/backup_lesson_stepslib.php

@@ -170,7 +170,14 @@ class backup_lesson_activity_structure_step extends backup_activity_structure_st
                   FROM {lesson_pages}
                  WHERE lessonid = ? ORDER BY prevpageid",
                 array(backup::VAR_PARENTID));
-        $answer->set_source_table('lesson_answers', array('pageid' => backup::VAR_PARENTID));
+
+        // We use SQL here as answers must be ordered by id so that the restore gets them in the right order
+        $answer->set_source_sql('
+                SELECT *
+                FROM {lesson_answers}
+                WHERE pageid = :pageid
+                ORDER BY id',
+                array('pageid' => backup::VAR_PARENTID));
 
         // Check if we are also backing up user information
         if ($this->get_setting_value('userinfo')) {