Just to add info about the first trouble (challenges?) I faced with my migrated DB:
When trying to upgrade my Mattermost 7.3.0 to 7.4.0 today Mattermost Boards refused to start, its DB migration failed.
The reason was the props attribute (normally JSON content) in the Users table, where (probably during the migration) some “null” Strings crept in (so no NULL SQL values, a literal String saying “null”).
This was easy to fix though:
UPDATE Users SET props = '{}' WHERE props = 'null';
Mattermost Boards / Focalboard startet fine afterwards.
I just hope there are not much more quirks like this hidden in the migrated data… :-/ That’s something I feared could happen with a migration approach like pg_loader. (If I didn’t just make a stupid mistake during migration, not sure…)
To help people googling for it, the error message I got was:
cannot activate plugin: error initializing the DB: driver: postgres, message: failed to execute migration, command: executing_query, originalError: pq: kann nicht aus skalarem Wert löschen, query: \n\n\n INSERT INTO Preferences (UserId, Category, Name, Value) SELECT Id, 'focalboard', 'welcomePageViewed', replace((Props->'focalboard_welcomePageViewed')::varchar, '\"', '') FROM Users WHERE Props->'focalboard_welcomePageViewed' IS NOT NULL ON CONFLICT DO NOTHING;\n INSERT INTO Preferences (UserId, Category, Name, Value) SELECT Id, 'focalboard', 'hiddenBoardIDs', replace(replace(replace((Props->'hiddenBoardIDs')::varchar, '\"[', '['), ']\"', ']'), '\\\"', '\"') FROM Users WHERE Props->'hiddenBoardIDs' IS NOT NULL ON CONFLICT DO NOTHING;\n INSERT INTO Preferences (UserId, Category, Name, Value) SELECT Id, 'focalboard', 'tourCategory', replace((Props->'focalboard_tourCategory')::varchar, '\"', '') FROM Users WHERE Props->'focalboard_tourCategory' IS NOT NULL ON CONFLICT DO NOTHING;\n INSERT INTO Preferences (UserId, Category, Name, Value) SELECT Id, 'focalboard', 'onboardingTourStep', replace((Props->'focalboard_onboardingTourStep')::varchar, '\"', '') FROM Users WHERE Props->'focalboard_onboardingTourStep' IS NOT NULL ON CONFLICT DO NOTHING;\n INSERT INTO Preferences (UserId, Category, Name, Value) SELECT Id, 'focalboard', 'onboardingTourStarted', replace((Props->'focalboard_onboardingTourStarted')::varchar, '\"', '') FROM Users WHERE Props->'focalboard_onboardingTourStarted' IS NOT NULL ON CONFLICT DO NOTHING;\n INSERT INTO Preferences (UserId, Category, Name, Value) SELECT Id, 'focalboard', 'version72MessageCanceled', replace((Props->'focalboard_version72MessageCanceled')::varchar, '\"', '') FROM Users WHERE Props->'focalboard_version72MessageCanceled' IS NOT NULL ON CONFLICT DO NOTHING;\n INSERT INTO Preferences (UserId, Category, Name, Value) SELECT Id, 'focalboard', 'lastWelcomeVersion', replace((Props->'focalboard_lastWelcomeVersion')::varchar, '\"', '') FROM Users WHERE Props->'focalboard_lastWelcomeVersion' IS NOT NULL ON CONFLICT DO NOTHING;\n\n UPDATE Users SET props = (props - 'focalboard_welcomePageViewed' - 'hiddenBoardIDs' - 'focalboard_tourCategory' - 'focalboard_onboardingTourStep' - 'focalboard_onboardingTourStarted' - 'focalboard_version72MessageCanceled' - 'focalboard_lastWelcomeVersion');\n \n\n \n\n \n\n\n