Error in modifying Object Value in Triggers defined on Object Tables

Question

Hi,
While practising with Triggers, the following error was encountered. Could anyone suggest what is the reason and solution for the problem.
An Object Type and an object Table are created.
create or replace
type typPerson is object
(id number,
firstname varchar2(30),
lastname varchar2(30)
create table person_obj_tab of typPerson
/Below is the trigger that modifies data according to some scenario.
Create Or Replace Trigger Trg_B_Iou_POT
before insert or update on  person_obj_tab
for each row
begin
  :new.object_value:= typperson(15,'Object1','Changed') ;
end;
/Trigger created.
I executed the below insert statement, and I got the following error.
SQL> insert into person_obj_tab values (10,'Object1','From Trigger');
insert into person_obj_tab values (10,'Object1','From Trigger')
ERROR at line 1:
ORA-03113: end-of-file on communication channel
Process ID: 4153
Session ID: 136 Serial number: 305
SQL> select 1 from dual;
ERROR:
ORA-03114: not connected to ORACLEBut when the trigger code is changed, the above insert statement works,
Create Or Replace Trigger Trg_B_Iou_POT
before insert or update on  person_obj_tab
for each row
begin
  :new.id:= 15;
  :new.firstname := 'Object1' ;
  :new.lastname := 'Changed';
end;
SQL> insert into person_obj_tab values (10,'Object','Original');
1 row created.
Question:
1) Trigger of version 1 did not report any error during compilation, but during DML execution, hangs for sometime and gives the above error.
2) Whether direct assignment of Objects of greater size is possible inside triggers built on object Tables?
3) Suppose an object contain multiple attributes (say more than 20), then how to assign them inside a trigger?
Thanks,
Sudher

Answer 1

Hi Sudher,
I have at least one possible reason for this behaviour.
The pseudo-column object_value returns system-generated names for the columns of an object table.
I don't know if you can use it for a complete instance you want to modify.
And I recognized that you don't use the constructor for inserting data in your table.
Why not?
Following suggestion:
create or replace
type typPerson is object
(id number,
firstname varchar2(30),
lastname varchar2(30)
create table person_obj_tab of typPerson
Create Or Replace Trigger Trg_B_Iou_POT
before insert or update on  person_obj_tab
for each row
begin
  :new.id := 15;
  :new.firstname := 'Object1';
  :new.lastname := 'Changed';
end;
insert into person_obj_tab values (typperson(10,'Object1','From Trigger'));
select * from person_obj_tab;When you modify the attributes always for themselves, it works.
Triggers in my opinion have the issue to modify or set some choosen columns, but not all.