I just realized there's a further problem in the area: when a partition is detached from its parent, its indexes are not made independent of the indexes on parent. So they can't be dropped on their own (booh!); and dropping the index on the former parent partitioned table drops the index on the former partition also (hiss!). I think the fix for this is to delete all dependencies, and re-register normal ones. Should be straightforward, but I'm not doing it this year.
-- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services