IPB4: merging forum permissions from IPB4 permantently breaks permissions on MyBB forums

[MildlyInterested]

1. Merge IPB4 forum/database
2. Import Forum permissions during merge
3. All forums are visible to any group regardless of settings.

Individual group permissions still work so if the "Guest" group has no permissions to view the board at all that still works. If permissions to view the board are granted they can see everything again.

I propose to either completely disable the forum permissions import in the ipb4 script or to put a big warning in front of it.

[MildlyInterested]

Solved the issue: If the forumpermissions table is bigger than 16MB (can be seen in Admin CP --> Tools --> Cache Manager) the cache breaks because the cache column in the mybb_datacache table is set to mediumtext which only accepts strings of up to 16MB. Solution is to change it to longtext which accepts strings up to 4GB.