What I want to do, is replacing some lossy files, with new lossless - but I don't want to lose the history of the songs.
Added date isn't touched here at all - that said, statistics will be some kind of wrong after using this function.
* Starting with an empty database.
* 2016-08-15: Adding 15 MP3 files
--> The filetype statistics shows that I've added these tracks on 2016-08-15.
* 2016-08-18: Replacing these 15 MP3 files by 15 FLAC files
--> The filetype statistics now shows that I've added 15 FLAC files on 2016-08-15 and no MP3 files at all.
Correct would be, if statistics shows 15 added MP3 files on 2016-08-15 and 15 deleted MP3 and 15 added FLAC files on 2016-08-18...
But to get this working, you would need another table in the database to track these values.
@Sven: Correctly observed, this is not possible at the moment since deletions/replacements are not tracked (and it might be a very hard task to do, since it affects more than just this function)