Add a comment explaining the use and doubts about this patch

diff --git a/modules/gmysqlbackend/enable-foreign-keys.mysql.sql b/modules/gmysqlbackend/enable-foreign-keys.mysql.sql
index 9ecdeb9c68f359facc3f82afc9349ab464d1cc54..391936c0062fd3e9be3783cfc08309db5c7edd5f 100644 (file)
--- a/modules/gmysqlbackend/enable-foreign-keys.mysql.sql
+++ b/modules/gmysqlbackend/enable-foreign-keys.mysql.sql
@@ -1,3 +1,13 @@
+/*
+Using this SQL causes Mysql to create foreign keys on your database. This will
+make sure that no records, comments or keys exists for domains that you already
+removed. This is not enabled by default, because we're not sure what the
+consequences are from a performance point of view. If you do have feedback,
+please let us know how this effects your setup.
+
+Please note that it's not possible to apply this, before you cleaned up your
+database, as the foreign keys do not exist.
+*/
 ALTER TABLE records ADD CONSTRAINT `records_domain_id_ibfk` FOREIGN KEY (`domain_id`) REFERENCES `domains` (`id`) ON DELETE CASCADE ON UPDATE CASCADE;
 ALTER TABLE comments ADD CONSTRAINT `comments_domain_id_ibfk` FOREIGN KEY (`domain_id`) REFERENCES `domains` (`id`) ON DELETE CASCADE ON UPDATE CASCADE;
 ALTER TABLE domainmetadata ADD CONSTRAINT `domainmetadata_domain_id_ibfk` FOREIGN KEY (`domain_id`) REFERENCES `domains` (`id`) ON DELETE CASCADE ON UPDATE CASCADE;