mysqldump creates conditional comments that lead to errors when restoring

[Jochen Kunze]

Hello,
I use mysqldump (Ver 10.13 Distrib 5.5.52, for solaris10 (i386)) to make dumps of my wordpress database. When I try to restore the dump with mysqldumper, there are several errors concerning conditional comments, which are inserted in the dump by mysql dump. Something like these:

/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `wp_commentmeta` (
`meta_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
...
...
KEY `meta_key` (`meta_key`(191))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_520_ci;
/*!40101 SET character_set_client = @saved_cs_client */;

or

/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

The error message is "Cannot set <variable_name> to null".

When I remove all these conditional comments the import is no problem and everything is fine.

My questions: Is it save to remove these comments or to force the import in case of SQL errors? Which function do these statements have?

I understand that some variables are stored and after all is done are restored. But Why?