Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

CHAPTER 8 ■ TRANSACTIONS 271
last_ddl_time = last_ddl_time + 1;
If we halted the UPDATE loop partway through, how would we restart it? We could not just
rerun it, as we would end up adding 2 to some dates, and 1 to others. If we fail again, we would
add 3 to some, 2 to others, 1 to the rest, and so on. We need yet more complex logic—some
way to “partition” the data. For example, we could process every OBJECT_NAME that starts with A,
and then B, and so on:
ops$tkyte@ORA10G> create table to_do
2 as
3 select distinct substr( object_name, 1,1 ) first_char
4 from T
5 /
Table created.
ops$tkyte@ORA10G> begin
2 for x in ( select * from to_do )
3 loop
4 update t set last_ddl_time = last_ddl_time+1
5 where object_name like x.first_char || '%';
6
7 dbms_output.put_line( sql%rowcount || ' rows updated' );
8 delete from to_do where first_char = x.first_char;
9
10 commit;
11 end loop;
12 end;
13 /
22257 rows updated
1167 rows updated
135 rows updated
1139 rows updated
2993 rows updated
691 rows updated
...
2810 rows updated
6 rows updated
10 rows updated
2849 rows updated
1 rows updated
2 rows updated
7 rows updated
PL/SQL procedure successfully completed.
Now, we could restart this process if it fails, since we would not process any object name
that had already been processed successfully. The problem with this approach, however, is
that unless we have some attribute that evenly partitions the data, we will end up having a