Inserting into a doubly nested table through an object view

Question

Can anyone give me an example of an INSTEAD OF trigger that will mediate an INSERT into a doubly nested table of an Object View? Is there syntax that will allow it?

Answer 1

Here's some code to demonstrate. Note that relational tables, not an object table, are used to store object instances:
create or replace type TInnerNestedTable
is table of varchar2(20)
create or replace type TOuterNestedTable
is table of TInnerNestedTable
create or replace type TMyObject
is object
     id     varchar2(20)
,     tab     TOuterNestedTable
create
table     T_MY_OBJECT
     id          varchar2(20)     not null
,     primary key (id)
create
table     T_MY_OBJECT_TAB_OUTER
     id          varchar2(20)     not null
,     outerIndex     integer          not null
,     primary key (id, outerIndex)
,     foreign key (id) references T_MY_OBJECT on delete cascade
create
table     T_MY_OBJECT_TAB_INNER
     id          varchar2(20)     not null
,     outerIndex     integer          not null
,     innerIndex     integer          not null
,     innerValue     varchar2(20)
,     primary key (id, outerIndex, innerIndex)
,     foreign key (id, outerIndex) references T_MY_OBJECT_TAB_OUTER on delete cascade
create or replace view V_MY_OBJECT
of TMyObject
with object identifier (id)
as
select     t.id
,     cast(multiset(
          select     cast(multiset(
                    select     i.innerValue
                    from     T_MY_OBJECT_TAB_INNER i
                    where     i.id = o.id
                    and     i.outerIndex = o.outerIndex
               ) as TInnerNestedTable)
          from     T_MY_OBJECT_TAB_OUTER o
          where     o.id = t.id
     ) as TOuterNestedTable)
from     T_MY_OBJECT t
create or replace trigger TR_II_V_MY_OBJECT
instead of insert on V_MY_OBJECT
for each row
begin
     insert
     into     T_MY_OBJECT
          id
     values     (
          :new.id
     insert
     into     T_MY_OBJECT_TAB_OUTER
          id
     ,     outerIndex
     select     :new.id
     ,     rownum
     from     table(:new.tab) o;
     insert
     into     T_MY_OBJECT_TAB_INNER
          id
     ,     outerIndex
     ,     innerIndex
     ,     innerValue
     select     :new.id
     ,     o.outerIndex
     ,     rownum
     ,     value(i)
     from     (
          select     :new.id
          ,     rownum outerIndex
          ,     value(o) innerTab
          from     table(:new.tab) o
          ) o
     ,     table(o.innerTab) i;
end;
insert
into     V_MY_OBJECT
values     (
     new TMyObject(
          'A'
     ,     TOuterNestedTable(
               TInnerNestedTable('A','B','C')
          ,     TInnerNestedTable('AA')
          ,     TInnerNestedTable('AB')
insert
into     V_MY_OBJECT
values     (
     new TMyObject(
          'B'
     ,     TOuterNestedTable(
               TInnerNestedTable('X','Y','Z')
          ,     TInnerNestedTable('Hello', 'World!')
/Selecting from the view shows the results:
select     value(o)
from     V_MY_OBJECT o
VALUE(O)(ID, TAB)
TMYOBJECT('A', TOUTERNESTEDTABLE(TINNERNESTEDTABLE('A', 'B', 'C'), TINNERNESTEDTABLE('AA'), TINNERNESTEDTABLE('AB')))
TMYOBJECT('B', TOUTERNESTEDTABLE(TINNERNESTEDTABLE('X', 'Y', 'Z'), TINNERNESTEDTABLE('Hello', 'World!')))
2 rows selected.Hope that helps...
Gerard