Update taking too much time

Question

I have 2 tables
     clean_d(d_name,d_code) <D_CODE COLUMN IS BLANK>
     dict_d(d_name,dr_code).. d_name is primary key for dict_d table.
I have to join the tables on d_name field and update d_code column in clean_d with corresponding dr_code from dict_d.
the following query is been running for last 1 hr..
UPDATE CLEAN_D A SET
     A.D_CODE = ( SELECT B.DR_CODE FROM DICT_D B
     WHERE UPPER(A.D_NAME) = UPPER( B.D_NAME)) ;
using Oracle9i ..
Sugg. please ...
thanks in adv.
Regards,
ravi Kumar M

Answer 1

Hi,
you can use function-based indexes for those tables to improve query time.
--created 2 tables with ~10000 rows
create table clean_d(d_name varchar2(40), d_code int);
insert into clean_d select lower(object_name)||rownum, null from all_objects;
create unique index i1_clean_d on clean_d(d_name);
create table dict_d(d_name varchar2(40), dr_code int);
insert into dict_d select object_name||rownum, dbms_random.value(1, 100000) from all_objects;
create unique index i1_dict_d on dict_d(d_name);
exec dbms_stats.gather_table_stats(user, 'CLEAN_D', estimate_percent=>100, cascade=>true, method_opt=>'for all columns size 100')
exec dbms_stats.gather_table_stats(user, 'DICT_D', estimate_percent=>100, cascade=>true, method_opt=>'for all columns size 100')
explain plan for
UPDATE CLEAN_D A SET
A.D_CODE = ( SELECT B.DR_CODE FROM DICT_D B
WHERE UPPER(A.D_NAME) = UPPER( B.D_NAME))
| Id | Operation | Name | Rows | Bytes | Cost |
| 0 | UPDATE STATEMENT | | 10681 | 219K| 6 |
| 1 | UPDATE | CLEAN_D | | | |
| 2 | TABLE ACCESS FULL | CLEAN_D | 10681 | 219K| 6 |
|* 3 | TABLE ACCESS FULL | DICT_D | 107 | 2782 | 6 |
--Killed session after 5 minutes
oratest> UPDATE CLEAN_D A SET
2 A.D_CODE = ( SELECT B.DR_CODE FROM DICT_D B
3 WHERE UPPER(A.D_NAME) = UPPER( B.D_NAME))
4 /
UPDATE CLEAN_D A SET
ERROR at line 1:
ORA-00028: your session has been killed
Elapsed: 00:05:04.07
But if the FB indexes are created, the different plan will be created
create index f1_clean_d on clean_d(upper(d_name));
create index f1_dict_d on dict_d(upper(d_name));
exec dbms_stats.gather_index_stats(user, 'F1_CLEAN_D', estimate_percent=>100)
exec dbms_stats.gather_index_stats(user, 'F1_DICT_D', estimate_percent=>100)
PLAN_TABLE_OUTPUT
| Id | Operation | Name | Rows | Bytes | Cost |
| 0 | UPDATE STATEMENT | | 10681 | 219K| 6 |
| 1 | UPDATE | CLEAN_D | | | |
| 2 | TABLE ACCESS FULL | CLEAN_D | 10681 | 219K| 6 |
| 3 | TABLE ACCESS BY INDEX ROWID| DICT_D | 107 | 2782 | 2 |
|* 4 | INDEX RANGE SCAN | F1_DICT_D | 43 | | 1 |
Predicate Information (identified by operation id):
4 - access(UPPER("B"."D_NAME")=UPPER(:B1))
oratest> UPDATE CLEAN_D A SET
2 A.D_CODE = ( SELECT B.DR_CODE FROM DICT_D B
3 WHERE UPPER(A.D_NAME) = UPPER( B.D_NAME))
4 /
10681 rows updated.
Elapsed: 00:00:03.02
Ooops, only a couple of seconds.
Andrey