Performance Problem - "OR" condition

Question

All,
We have a query that is doing full outer join and the join condition has an "OR" condition
DB Version: 10.2.0.5
select /*+ opt_param('_optimizer_native_full_outer_join', 'force') */ *
from
tableA a
full outer join
tableB b
on
[(a.col1=b.col1) or (a.col2=b.col2) or (a.col3=b.col3)]
The above query is not using FULL HASH OUTER JOIN even when we forced it by using hint opt_param('_optimizer_native_full_outer_join', 'force')
even with the hint still the full outer join is executed as a union of left outer join and an anti-join
the above query taking 5 hrs to complete but when i remove the "OR" condition its running within 10 minutes(drastic chnage)
I used the following "OR" expansion:
select * from
{ select *
from
tableA a
full outer join
tableB b
on
(a.col1=b.col1) }
UNION
{ select *
from
tableA a
full outer join
tableB b
on
(a.col2=b.col2) }
UNION
{ select *
from
tableA a
full outer join
tableB b
on
(a.col3=b.col3) }
but by doing so it is using hash full outer join and query ran in just 10 minutes , but i am getting more rows than expected number of records
So please advice me on it, How can i make it work?
I will post explain plan and actual query if an one needed
Thanks

Answer 1

PLAN_TABLE_OUTPUT
Plan hash value: 3022803566
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 51095 | 8732K| | 15092 (1)| 00:04:32 |
| 1 | SORT UNIQUE | | 51095 | 8732K| 19M| 14311 (1)| 00:04:18 |
| 2 | VIEW | | 51095 | 8732K| | 13530 (1)| 00:04:04 |
| 3 | SORT UNIQUE | | 51095 | 93M| 199M| 13530 (1)| 00:04:04 |
| 4 | UNION-ALL | | | | | | |
| 5 | VIEW | | 51093 | 93M| | 5440 (2)| 00:01:38 |
| 6 | UNION-ALL | | | | | | |
|* 7 | FILTER | | | | | | |
| 8 | NESTED LOOPS OUTER | | 51090 | 10M| | 5303 (2)| 00:01:36 |
| 9 | TABLE ACCESS FULL | TABLE1 | 1310 | 134K| | 4 (0)| 00:00:01 |
| 10 | VIEW | | 39 | 4368 | | 4 (0)| 00:00:01 |
|* 11 | TABLE ACCESS FULL| TABLE2 | 39 | 4368 | | 4 (0)| 00:00:01 |
|* 12 | FILTER | | | | | | |
|* 13 | TABLE ACCESS FULL | TABLE2 | 66 | 7392 | | 4 (0)| 00:00:01 |
|* 14 | TABLE ACCESS FULL | TABLE1 | 39 | 4095 | | 4 (0)| 00:00:01 |
| 15 | FAST DUAL | | 1 | | | 2 (0)| 00:00:01 |
| 16 | FAST DUAL | | 1 | | | 2 (0)| 00:00:01 |
Even with hints in place its doing nested loop outer join
but when i remove the OR condition in join condition its using hash outer join
Edited by: rcc50886 on Jan 24, 2012 1:01 PM