Merge pull request #1135 from noplanman/1125-fix_migration_script

Fix migration script for older versions of MySQL.

Author: noplanman

CHANGELOG.md

@@ -11,6 +11,7 @@ Exclamation symbols (:exclamation:) note something of importance e.g. breaking c
 ### Deprecated
 ### Removed
 ### Fixed
+- Correct SQL migration script for older versions of MySQL.
 ### Security
 
 ## [0.63.1] - 2020-06-24

utils/db-schema-update/0.62.0-0.63.0.sql

@@ -5,7 +5,10 @@ ALTER TABLE `poll` ADD COLUMN `close_date` timestamp NULL DEFAULT NULL COMMENT '
 
 ALTER TABLE `poll_answer` DROP PRIMARY KEY, ADD PRIMARY KEY (`poll_id`, `user_id`);
 
-ALTER TABLE `message` DROP CONSTRAINT `message_ibfk_6`;
+ALTER TABLE `message`
+    DROP FOREIGN KEY IF EXISTS `message_ibfk_6`,
+    DROP INDEX IF EXISTS `message_ibfk_6`;
+
 ALTER TABLE `message`
     ADD COLUMN `via_bot` bigint NULL DEFAULT NULL COMMENT 'Optional. Bot through which the message was sent' AFTER `reply_to_message`,
     ADD KEY `via_bot` (`via_bot`),