I've been trying to find out of a while now if there are any plans (or work in progress) for allowing Calibre to use a different database than SQLite; I didn't have much success
, maybe someone can answer this for me?
I might be able/willing to help such an effort.
As a side note, for me, the database is one of the major issues of Calibre: I have a large collection of about 15000 books, *lots* of tags, authors, etc. and almost all operations involving the database are slow: searching, adding new books, e.g. right now calibre is frozen for >15 minutes after trying to delete about 1000 tags at once... (and no, my computer is not old/slow, has plenty of ram, disks defragged, etc.
)