Re: Massive Update commit every 1000 records
- From: Alex Fatkulin <afatkulin@xxxxxxxxx>
- To: wellmetus@xxxxxxxxx
- Date: Fri, 13 Nov 2009 15:16:19 -0500
There could be a couple of answers which depend on how your table is organized.
If you have an index on SSN then one of the things you might try is a
simple loop like that:
begin
loop
update sales set ssn=mod(ssn, 10000)
where ssn > 9999
and rownum <= 1000;
commit;
exit when sql%rowcount < 1000;
end loop;
end;
though that might be slow in certain cases (if your clustering factor
for ssn isn't good, for example).
You might try bulk collect/update a shot and see how something like
this will perform for you:
declare
cursor l_cur is select rowid from sales where ssn > 9999;
type l_tab is table of rowid index by binary_integer;
l_buffer l_tab;
begin
open l_cur;
loop
fetch l_cur bulk collect into l_buffer limit 1000;
forall i in 1 .. l_buffer.count
update sales set ssn=mod(ssn,10000) where
rowid=l_buffer(i);
commit;
exit when l_buffer.count < 1000;
end loop;
close l_cur;
end;
that should be faster compared to row-by-row stuff in your example.
Another thing you could consider is dong CTAS and then swapping the tables.
On Fri, Nov 13, 2009 at 2:50 PM, Roger Xu <wellmetus@xxxxxxxxx> wrote:
> Hi List,
>
> Background: 9i (9.2.0.8.0) HP-UX B.11.31 U ia64
>
> We need to shrink SSN to the last 4 digit.
>
> update sales set ssn=to_number(substr(to_char(ssn),-4));
>
> But the sales table is quite large and we want to commit every 1000 records.
>
> Does anyone have a better idea to do this rather than below?
>
> Thanks,
>
> Roger
>
>
> declare
> cursor c12 is select ssn from sales for update of ssn;
> n number := 0;
> begin
> for eachc12 in c12 loop
> if eachc12.ssn is not null then
> n := n + 1;
> update sales set ssn=to_number(substr(to_char(ssn),-4)) where current
> of c12;
> if ( n = 1000 )
> then
> commit;
> end if;
> end if;
> end loop;
> commit;
> end;
>
--
Alex Fatkulin,
http://afatkulin.blogspot.com
http://www.linkedin.com/in/alexfatkulin
--
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