ALTER TABLE book MODIFY COLUMN book_type VARCHAR(32);
ALTER TABLE library MODIFY COLUMN icon VARCHAR(255);
ALTER TABLE shelf MODIFY COLUMN icon VARCHAR(255);
ALTER TABLE book_metadata MODIFY COLUMN language VARCHAR(255);
ALTER TABLE book_metadata MODIFY COLUMN cover VARCHAR(1000);
ALTER TABLE pdf_viewer_preference MODIFY COLUMN zoom VARCHAR(64);
ALTER TABLE pdf_viewer_preference MODIFY COLUMN spread VARCHAR(64);
ALTER TABLE epub_viewer_preference MODIFY COLUMN theme VARCHAR(255);
ALTER TABLE epub_viewer_preference MODIFY COLUMN font VARCHAR(255);