Yes, weird, original here for people who want to actually be able to read it 
It might be. This migration deletes versioned cache views that have _x tacked to the end (where x is a digit). But the table that it misses is an unversioned table (without _x).
@sheng_hualuo can you try running this from a rails console?
DiscourseGamification::LeaderboardCachedView.regenerate_all