Bulk Collect in Oracle PL/SQL

Below are some examples:

create table BULK_COLLECT_TEST as select * from PER_ALL_PEOPLE_F;

Table created.

insert into BULK_COLLECT_TEST

select * from BULK_COLLECT_TEST;

20000 rows created.

--BLOCK1:Using Loops
declare
 cursor c1
 is select object_name from BULK_COLLECT_TEST;
 rec1 c1%rowtype;
 begin
      open c1;
    loop
       fetch c1 into rec1;
    exit when c1%notfound;
    null;
    end loop;
 end;

total Elapsed Time is : 45 Secs

--BLOCK2: Using Bulk Collecting
declare
  cursor c1 is select object_name from BULK_COLLECT_TEST;
  type c1_type is table of c1%rowtype;
  rec1 c1_type;
begin
open c1;
   fetch c1 bulk collect into rec1;
end;

total Elapsed Time is : 5 Sec

So bulk collecting the rows shows a huge performance improvement over fetching row by row.

Some cases there are many rows to process, we can limit the number of rows to bulk collect, process those rows and fetch again.
Otherwise process memory gets bigger and bigger as you fetch the rows.

--Bulk Collect Example using LIMIT :
declare
 cursor c1 is select object_name from BULK_COLLECT_TEST;
 type c1_type is  table of c1%rowtype;
 rec1 c1_type;
begin
    open c1;
    loop
    fetch c1 bulk collect into rec1 limit 200;
    for i in 1..rec1.count loop
    null;
    end loop;
    exit when c1%notfound;
    end loop;
end;


Example:-
-----------

declare
type array is table of number index by binary_integer;
l_data array;
cursor c is select empno from emp;
begin
open c;
loop
fetch c bulk collect into l_data limit 10;
if ( c%notfound )
then
dbms_output.put_line
( 'Cursor returned NOT FOUND but array has ' || l_data.count
|| ' left to process' );
else
dbms_output.put_line
( 'We have ' || l_data.count
|| ' to process' );
end if;
exit when c%notfound;
end loop;
close c;
end;