Thanks kovidgoyal ..
Sure .. I just want to modify my own local library with these custom values. Also, this is for one time only, i.e. download metadata, save values in custom columns, revert back my code changes.
For me, I followed
http://manual.calibre-ebook.com/sub_groups.html and created custom column with lookup key "#genre", heading as "Genre" and type as "Comma-separated text, like tags, shown in the tag browser". My question is how to save (the shown sample static data) in database ?
Another question, is it possible to escape commas and dots characters in values in this genre column ?
Thanks