Strange behavior with large Object Types

Question

I recognized that calling a method on an Oracle Object Type takes longer when the instance gets bigger.

The code below just adds rows to a collection stored in the Object Type and calls the empty dummy-procedure in the loop.

Calls are taking longer when more rows are in the collection. When I just remove the call to dummy, performance is much better (the collection still contains the same number of records):

Calling dummy:               Not calling dummy:
11                           0
81                           0
158                          0

Code to reproduce:

Create Type t_tab Is Table Of VARCHAR2(10000);

Create Type test_type As Object(
  tab t_tab,
  Member Procedure dummy
);

Create Type Body test_type As
  Member Procedure dummy As Begin
    Null;  --# Do nothing
  End dummy;
End;


Declare
  v_test_type  test_type := New test_type( New t_tab() );

  Procedure run_test As
    start_time  NUMBER := dbms_utility.get_time;
  Begin
    For i In 1 .. 200 Loop
      v_test_Type.tab.Extend;
      v_test_Type.tab(v_test_Type.tab.Last) := Lpad(' ', 10000);
      v_test_Type.dummy();  --# Removed this line in second test
    End Loop;
    dbms_output.put_line( dbms_utility.get_time - start_time );
  End run_test;

Begin
  run_test;
  run_test;
  run_test;
End;

I tried with both 10g and 11g.
Can anyone explain/reproduce this behavior?

Answer 1

Found out myself, the problem is described in Using SELF IN OUT NOCOPY with Member Procedures:

In member procedures, if SELF is not declared, its parameter mode defaults to IN OUT.

So with every procedure call my whole object was copied twice, and as size was increasing this took longer and longer.

---

The solution is to use SELF IN OUT NOCOPY test_type as first parameter of my procedure declaration:

Create Type test_type As Object(
  tab t_tab,
  Member Procedure dummy(SELF IN OUT NOCOPY test_type)
);

and is still called without parameter

v_test_type.dummy();

---

Performance is back to normal:

0
0
0