Originally Posted by Dopedangel
Currently calibre cant import metadata from file names to custom columns. If it could do that having a specific old filename column would not be needed. As a workaround if you don't use the publisher field you could use that to import file-names.
File-names usually do not have publisher fields and you need the original file-names to correct your library so once you are done you can update the publisher field.
Dopedangel the problem arises in the scenario where:
1) You read metadata from the books and you don't use Regular Expressions.
In the scenario where you read directly from filename your suggestion is good.