Question

I’m working on oracle 9i. I have a table with 135,000,000 records, partitioned where each partition having approx. 10,000,000 rows. all indexed and everything.

I need to delete around 70,000,000 rows from this as the new business requirement.

So I created a backup of the rows to be deleted as separate table.

Table1 <col1, col2........> -- main table (135,000,000 rows)

Table2 <col1, col2........> -- backup table (70,000,000 rows)

Tried the below delete query.

Delete from table1 t1 where exists (select 1 from table2 t2 where t2.col1 = t1.col1)

but it takes infinite hours.

then tried

declare
cursor c1 is 
select col1 from table2;
c2 c1%rowtype;
cnt number;
begin
cnt :=0;
open c1;
loop
    fetch c1 into c2;
    exit when c1%notfound;

    delete from table1 t1 where t1.col1 = c2.col1;
    if cnt >= 100000 then
        commit;
    end if;
    cnt:=cnt+1;
end loop;
close c1;
end;

even still its been running for more than 12 hours. and still not completed.

Please note that there are multiple indexes on table1 and an index on col1 on table2. all the tables and indexes are analysed.

Please advise if there is any way of optimizing for this scenario.

Thanks guys.

Answer 1

Drop all indexes (backup the create statements)
Use the select statement that used to build the backup table, create from it a DELETE command
Recreate all index