Why doesnt partiotining elimination work?

First I do this..

a) create table a1 as select * from old_a where year = 1998
b) create table a2 as select * from old_a where year = 1999
c) create view v_a as select * from a1 union select * from a2
d) create check contraint on a1 (year = 1998)
e) create check contraint on a2 (year = 1999)
f) create primary keys on a1.year and a2.year

If I do...
Select * on v_a where year = 1999

The explain plan show that I access both tables a1 and a2; Why?
Oracle does partiotining elimination when having check contraints or not???
Help!!
Thanks
Marcus Received on Mon Aug 02 1999 - 14:44:44 CDT