Instead of trigger is NOT firing for merge statements in Oracle 10gR2

Question

The trigger fires fine for a update statement, but not when I use a merge statement
with an update clause. Instead I get the normal error for the view ( which is a union all view, and therefore not updatable.)
The error is :-
ORA-01733: virtual column not allowed here
oracle release is 10.2.0.2 for AIX 64L
Is this a known bug ?
I've used a multi-table insert statement to work around the problem for inserts, but
for updates, I'd really like to be able to use a merge statement instead of an update.
Mark.

Answer 1

This is my cut-down version :-
In this case case I'm getting an :-
ORA-01446: cannot select ROWID from, or sample, a view with DISTINCT, GROUP BY, etc.
rather then the ora-01733 error I get in the real code ( which is an update from an involved
XML expression - cast to a table form)
create table a ( a int primary key , b char(30) ) ;
create table b ( a int primary key , b char(30) ) ;
create view vw_a as
select *
from a
union all
select *
from b ;
ALTER VIEW vw_a ADD (
PRIMARY KEY
(a) DISABLE);
DROP TRIGGER TRG_IO_U_ALL_AB;
CREATE OR REPLACE trigger TRG_IO_U_ALL_AB
instead of update ON vw_a
for each row
begin
update a targ
set b = :new.b
where targ.a = :new.a
if SQL%ROWCOUNT = 0
then
     update b targ
     set b      = :new.b
     where targ.a = :new.a
end if ;
end ;
insert into a values (1,'one');
insert into a values (2,'two');
insert into a values (3,'three');
insert into b values (4,'quatre');
insert into b values (5,'cinq');
insert into b values (6,'six');
commit;
create table c as select a + 3 as a, b from a ;
commit;
merge into vw_a targ
using (select * from c ) src
on ( targ.a = src.a )
when matched
then update
set targ.b = src. b
select * from vw_a ;
rollback ;
update vw_a b
set b = ( select c.b from c where b.a = c.a )
where exists ( select c.b from c where b.a = c.a ) ;
select * from vw_a ;
rollback ;