Comment 7 for bug 1253637

The problem isn't the db, although IIRC sqlite does not enforce type
constraints, so it is possible to store floats in an integer column.
However, calibre code in general treats ratings as floating points in
many contexts, for example when calculating averag4e ratings in the Tag
Browser. Therefore, it is better to code defensively and explicitly
convert to int, so you can be sure of what you get.