SQL tuning suggestions.

Question

Hi
I am not a sql programmer and developers have given me this sql to have a look. I made the following recommendations after going through the sql. Is there anything else that can be added . I did not add about stats because they are representative and up to date.
SELECT /*+ PARALLEL(q1,4) */ *
FROM
(SELECT /*+ FIRST_ROWS(20) */
br.resource_id,
br.resource_code,
x.resource_seq_num employee_resource_number,
br.organization_id,
bd.department_id,
bd.department_code,
pf.full_name employee_name,
(SELECT xxdl_eam_util_pkg.xxdl_eam_get_resource_code(pf.person_id, bd.department_id)
FROM dual)
maximum_cost_resource,
pf.person_id,
x.wip_entity_id wo_id,
(SELECT weo1.wip_entity_name
FROM wip_eam_work_orders_v weo1
WHERE weo1.wip_entity_id = x.wip_entity_id)
wo_number,
CAST(x.start_date AS
TIMESTAMP) start_date,
CAST(x.completion_date AS
TIMESTAMP) completion_date,
wor.operation_seq_num wo_operation_number,
wor.resource_seq_num wo_resource_number,
wor.usage_rate_or_amount HOURS,
BRE.effective_start_date instance_start_date,
BRE.effective_end_date instance_end_date,
BRE.instance_id,
crc.resource_rate AS
resource_cost,
(SELECT xxdl_eam_util_pkg.xxdl_eam_get_all_res_code(pf.person_id, bd.department_id)
FROM dual)
all_resources
FROM per_all_people_f pf,
wip_eam_work_orders_v weo,
wip_operations wo,
wip_operation_resources wor,
(SELECT instance_id,
wip_entity_id,
operation_seq_num,
resource_seq_num,
start_date,
completion_date
FROM wip_op_resource_instances_v) x,
bom_dept_res_instances bdri,
bom_resource_employees BRE,
bom_department_resources bdr,
bom_resources br,
cst_resource_costs crc,
bom_departments bd
WHERE br.organization_id = bd.organization_id
AND bdr.resource_id = br.resource_id
AND bdr.department_id = bd.department_id
AND BRE.resource_id = br.resource_id
AND pf.effective_start_date <=sysdate
AND pf.effective_end_date >= sysdate
AND pf.person_id = BRE.person_id
AND wo.department_id = bd.department_id
AND wor.operation_seq_num(+) = wo.operation_seq_num
AND wor.wip_entity_id(+) = wo.wip_entity_id
AND wor.organization_id(+) = wo.organization_id
AND weo.wip_entity_id = wo.wip_entity_id
AND weo.organization_id = wo.organization_id
-- AND weo.organization_id = 6921
AND DECODE(bd.disable_date,null, sysdate,bd.disable_date) >= sysdate
AND DECODE(br.disable_date,null, sysdate,br.disable_date) >= sysdate
AND DECODE(wo.disable_date,null, sysdate,wo.disable_date) >= sysdate
AND crc.resource_id(+) = BRE.resource_id
AND x.wip_entity_id = wor.wip_entity_id
AND x.operation_seq_num = wor.operation_seq_num
AND x.resource_seq_num = wor.resource_seq_num
AND x.instance_id(+) = BRE.instance_id
AND bdri.department_id = bd.department_id
AND bdri.resource_id = br.resource_id
AND weo.organization_id = 6921
AND bdri.department_id = 5004
UNION
SELECT /*+ FIRST_ROWS(20) */ DISTINCT NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
pf.full_name employee_name,
NULL,
pf.person_id,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL HOURS,
NULL,
NULL,
NULL,
NULL,
NULL
FROM per_all_people_f pf,
wip_eam_work_orders_v weo,
wip_operations wo,
wip_operation_resources wor,
bom_dept_res_instances bdri,
bom_resource_employees BRE,
bom_department_resources bdr,
bom_resources br,
cst_resource_costs crc,
bom_departments bd
WHERE br.organization_id = bd.organization_id
AND bdr.resource_id = br.resource_id
AND bdr.department_id = bd.department_id
AND BRE.resource_id = br.resource_id
AND pf.effective_start_date <=sysdate
AND pf.effective_end_date >= sysdate
AND pf.person_id = BRE.person_id
AND wo.department_id = bd.department_id
AND wor.operation_seq_num(+) = wo.operation_seq_num
AND wor.wip_entity_id(+) = wo.wip_entity_id
AND wor.organization_id(+) = wo.organization_id
AND weo.wip_entity_id = wo.wip_entity_id
AND weo.organization_id = wo.organization_id
AND DECODE(bd.disable_date,null, sysdate,bd.disable_date) >= sysdate
AND DECODE(br.disable_date,null, sysdate,br.disable_date) >= sysdate
AND DECODE(wo.disable_date,null, sysdate,wo.disable_date) >= sysdate
AND crc.resource_id(+) = BRE.resource_id
AND bdri.department_id = bd.department_id
AND bdri.resource_id = br.resource_id
AND weo.organization_id = 6921
AND bdri.department_id = 5004
AND NOT EXISTS
(SELECT instance_id,
wip_entity_id operation_seq_num,
resource_seq_num
FROM wip_op_resource_instances_v)
) q1
ORDER BY department_id,
resource_code,
employee_name,
wo_number
My suggestions:
. Try to use UNION ALL instead of UNION. If you can eliminate UNION all together and flatten the query that will be even better.
2. You are using the function in a select statement xxdl_eam_util_pkg.xxdl_eam_get_resource_code(pf.person_id, bd.department_id)This will slow the performance. Try to get rid of this. Function calls in select are expensive.
3. Dont use the parallel hint and optimize. It wont get you consistent results.
4. Use of per_all_people_F is expensive. The UNION again complicates things. per_all_people_f has to be scanned 2x times.
5. Where does the application get the values for department id? Whether user inputs a value or whether it is hard coded . Most likely user will input value and each time it may be different. If that is the case, then you may be hitting bind peeking. There is not much hope for this. Not much can be done. Whatever you do this can happen. Only way is to pin the plan if you can use literals instead of binds. But that is not possible I think.
6. AND DECODE(bd.disable_date,null, sysdate,bd.disable_date) >= sysdate
AND DECODE(br.disable_date,null, sysdate,br.disable_date) >= sysdate
AND DECODE(wo.disable_date,null, sysdate,wo.disable_date) >= sysdate
Those statements, if you can rewrite would be good. If there are indexes on any of those columns, they are more than likely not used.
7. Are the outer joins really required. If not required remove them.
8. There is a 'WITH' clause in 10g . Try to use that for your subqueries or main query where applicable. It will save some I/O.
9. Try to tune without any hints. Remove the first rows as well and see the difference.
I know that the sql is definately bad and can be rewritten but I am not able to exactly write it for them.
Any inputs or thoughts?
MSK

Answer 1

Hi,
Any suggestions for reading on Sql tuning
I am looking for a practical book with solutions .
And books showing the Sql internal workings ?Take a look on Amazon some Jonathan Lewis books.
I will also recommend you to take a look on the following blogs:
- http://jonathanlewis.wordpress.com/
- http://www.juliandyke.com/
- http://richardfoote.wordpress.com/
- http://tkyte.blogspot.com/
And also any good interview based good Oracle DBA books ?You can take a look on my blog for some common DBA interview questions.
http://oraclenz.com/category/interview-tips/
Regards,
Francisco Munoz Alvarez
www.oraclenz.com