[Man Eating Duck]

Originally Posted by kovidgoyal

It's been many years since the first version of custom column code was written, but the current code most definitely creates uniqueness constraints, as you can see in lines 885 onwards in db/backend.py

I suggest you create a new custom column, copy over the values using metadata search and replace and delete the old one.

That right, and as I said the old library never gave me any problems during regular use either. I have quite a few custom columns which makes manual duplication a tedious task, but luckily my library is not enormous, so copying to a new library is already finished.

Thanks to you both!