Breaking a single query using for loop to improve performance

Question

Hi,
This is a continuation of my previous post which I marked Answered and few things are were left from my side and I was advised to post a new thread...
[Will it be a good ply|http://forums.oracle.com/forums/thread.jspa?threadID=880922&tstart=0]
will it be applicable to any query because I took this to simplify the thing to explain my case
which is actually........... pull the data from some tables using joins and insert into some other tables .....
I used few procedures for diff conditions one of them use plain' insert into select' and others use bulk collect technique.
I followed the simple strategy (for DML ) by Tom Kytes ..and Steven Feuerstein
Use single statement whenever it is possible..
if not use PL/SQL with bulk collect to avoid for loop.
Please correct me if I am wrong.
Thanks and Regards,
Hesh.

Answer 1

A simple test can prove the case
SQL> set serveroutput on
SQL>
SQL> create table t
  2  as
  3  select * from all_objects where 1=2
  4  /
Table created.
SQL> declare
  2    ltime integer;
  3  begin
  4      ltime := dbms_utility.get_time;
  5      insert into t select * from all_objects;
  6      ltime := dbms_utility.get_time - ltime;
  7
  8      dbms_output.put_line(ltime);
  9  end;
10  /
187
PL/SQL procedure successfully completed.
SQL> rollback
  2  /
Rollback complete.
SQL> declare
  2      ltime integer;
  3      type tbl is table of t%rowtype index by pls_integer;
  4      l_tbl tbl;
  5      cursor c
  6      is
  7      select * from all_objects;
  8  begin
  9      ltime := dbms_utility.get_time;
10      open c;
11      loop
12          fetch c bulk collect into l_tbl limit 500;
13          exit when c%notfound;
14
15          forall i in 1..l_tbl.count
16            insert into t values l_tbl(i);
17      end loop;
18
19      ltime := dbms_utility.get_time - ltime;
20
21      dbms_output.put_line(ltime);
22  end;
23  /
390
PL/SQL procedure successfully completed.
SQL> rollback
  2  /
Rollback complete.