Mattermost restore fails for Gitlab 18.5.0-ce.0 Omnibus

Hi,

I moved Gitlab 18.5.0-ce.0 Omnibus from Ubuntu 20.04 to an other server running Ubuntu 24.04. All worked like a charm excepted for Mattermost restore.

The backup / restore process followed : https://docs.gitlab.com/integration/mattermost/#back-up-gitlab-mattermost

When i try to restore the db SQL file i am getting many of the following errors :

ERROR:  must be owner of schema public
ERROR:  permission denied for schema public
ERROR:  type "public.channel_bookmark_type" does not exist
ERROR:  permission denied for schema public
ERROR:  type "public.channel_type" does not exist
ERROR:  permission denied for schema public

So checking the PostreSQL version 16.10. PostgreSQL 16 introduced a change to the rules around role permissions. And so i applied the fix given here : https://forum.mattermost.com/t/pq-permission-denied-for-schema-public/14273

GRANT ALL ON DATABASE mattermost_production TO gitlab_mattermost;
ALTER DATABASE mattermost_production OWNER TO gitlab_mattermost;
GRANT USAGE, CREATE ON SCHEMA PUBLIC TO gitlab_mattermost;

Then i tried again to restore. For now i am getting the following error :

sudo -u mattermost sh -c "zcat mattermost_dbdump_2025-10-21.sql.gz | /opt/gitlab/embedded/bin/psql -U gitlab_mattermost -h /var/opt/gitlab/postgresql -p 5432 mattermost_production"
SET
SET
SET
SET
SET
 set_config 
------------
 
(1 row)

SET
SET
SET
SET
ERROR:  must be able to SET ROLE "gitlab-psql"
ERROR:  type "channel_bookmark_type" already exists
ALTER TYPE
ERROR:  type "channel_type" already exists

Regards