Fast Updates for 8 million records..!!

Question

Hi All,
I was wondering is there any fast method for updating 8 million records out of 10 million table?
For eg :
I am having a customer table of 10m records and columns are cust_id, cust_num and cust_name.
i need to update 8m records out of 10m customer table as follows.
update customer set cust_id=46 where cust_id=75;
The above statement will update 8m records. And cust_id is indexed.
But if i fire the above update statement we'll face rollback segment problem..
Even if i use ROWNUM and commit after 100K records still its gonna take huge time and also i know CTAS will be lot lot faster but for this scenario i guess its not possible.. Right?
Any help is much appreciated...
Thanks.

Answer 1

You didn't specify what version you're on, but have you looked at dbms_redefinition?
create table cust (cust_num number, constraint cust_pk primary key (cust_num), cust_id number, name varchar2(10));
create index cust_id_idx on cust(cust_id);
insert into cust values( 1, 1, 'a');
insert into cust values( 2, 2, 'b');
insert into cust values( 3, 1, 'c');
insert into cust values( 4, 4, 'd');
insert into cust values( 5, 1, 'e');
select * From cust;
create table cust_int (cust_num number, cust_id number, name varchar2(10));
exec dbms_redefinition.start_redef_table(user,'cust', 'cust_int', 'cust_num cust_num, decode(cust_id, 1, 99, cust_id) cust_id, name name');
declare
i pls_integer;
begin
dbms_redefinition.copy_table_dependents( user, 'cust', 'cust_int', copy_indexes=>dbms_redefinition.cons_orig_params, copy_triggers=>true, copy_constraints=>true, copy_privileges=>true, ignore_errors=>false, num_errors=>i);
dbms_output.put_line('Errors: ' || i);
end;
exec dbms_redefinition.finish_redef_table(user, 'cust', 'cust_int');
select * From cust;
select table_name, index_name from user_indexes;
You would probably want to run a sync_interim_table in there before the finish.
Good luck.