The paths in the database now are relative of the config BOOKS_PATH and COVER_PATH
For updating the database this query should be use:
for (var i = db.books.find(); i.hasNext(); ) {
var book = i.next();
db.books.update({_id: book["_id"]}, {$set: {path: book["path"].slice(6), cover: book["cover"].slice(7), coversmall: book["coversmall"].slice(7)}});
}
