Is limiting needed in forall statements?

Question

Hello,
Could you please help me understand what the advantage is (if any) of looping and limiting during forall updates? I saw this simplified version in one the programs here at work and don't understand what the looping and limiting is for.
declare
cursor c1 is
select column1, column2 from tablea;
type aaa is table of c1%rowtype;
var1 aaa;
begin
open c1;
loop
fetch bulk collect into var1 limit 2500;
forall i in var1.first .. var1.last
update tableb
set column2 = var1(i).column2
where column1 = var1(i).column1;
exit when var1.count < 2500;
end loop;
close c1;
end;

Answer 1

arizona9952 wrote:
Hello,
Could you please help me understand what the advantage is (if any) of looping and limiting during forall updates? I saw this simplified version in one the programs here at work and don't understand what the looping and limiting is for.The advantage is that you can control the amount of memory your process needs to consume (PGA). There is a finite amount on every system, the amount available to you will depend on a number of factors (do some research if you're interested in this).
In my opinion you should always be using LIMITs when performing bulk operations.
As an aside, the code you've posted could be done as a single UPDATE statement (or MERGE), in about 95% of the cases you'll be better off with a single SQL statement if you can get away with it.