[HACKERS] Partitioning vs ON CONFLICT

Hi,

At the moment, partitioned tables have a restriction that prevents
them allowing INSERT ... ON CONFLICT ... statements:

postgres=# INSERT INTO cities SELECT 1, 'Crawley',105000 ON CONFLICT
(city_id) DO NOTHING;
ERROR:  ON CONFLICT clause is not supported with partitioned tables

Why do we have such a restriction?  And what would it take to remove it?

Thanks

Thom