We have similar problem and now we are try to find solution. When you
execute query on partion there is no sorting - DB use index to
retrieve data and if you need let say 50 rows it reads 50 rows using
index. But when you execute on parent table query optymizer do this:
-> Sort (cost=726844.88..748207.02 rows=8544855 width=37739)
(actual time=149864.868..149864.876 rows=50 loops=1)
it means 8544855 rows should be sorted and it takes long minutes. We
have simpler situation than you and I will try to find solution
tommorow :)
Michal Szymanski
http://blog.szymanskich.net
http://techblog.freeconet.pl/