Please list the releases that have been downloaded for more than 20000 times.
releases refer to groupName; downloaded for more than 20000 times refers to totalSnatched > 20000;
SELECT groupName FROM torrents WHERE totalSnatched > 20000
database name:db_id music_tracker
torrents table torrents Cols: groupName dtype text, totalSnatched dtype integer, artist dtype text, groupYear dtype integer, releaseType dtype text, groupId dtype integer, id dtype integer, 
tags table tags Cols: index dtype integer, id dtype integer, tag dtype text, 
