Performance with null parameters

Question

The below is the main cursor for a small report with some horrible performance. The report is taking 30 to 40 minutes to generate just a few rows of data. After checking my joins and whether the indexes were correct and all the other simple things, I began removing the lines on the bottom that are just used to insert incoming parameters. What I found is that if I comment out the two lines on the bottom of the statement (with v_person_id and v_sup_id), the query returns immediately if I pass a start and end date only and leave the other parameters as null. If I run the query with those lines in and pass null for those values also, it goes back to 30 minutes or so. I am confused as passing them as null should make the line evaluate to ppf.person_id = ppf.person_id. We use this technique with all of our reporting when we pass null values but for some reason it is failing horribly in this query. Can anyone see what I am doing wrong?
SELECT ppf.employee_number,
        ppf.full_name,
        loc.attribute3,
        loc.location_code,
        glc.segment1,
        glc.segment2,
        glc.segment3,
        org.name,
        (SELECT ppf1.employee_number||'~'||ppf1.full_name
             FROM per_all_people_f ppf1
            WHERE trunc(sysdate) between ppf1.effective_start_date and ppf1.effective_end_date
              AND ppf1.person_id = asg.supervisor_id
               AND rownum = 1) supervisor,
        past.per_system_status,
        hts.approval_status
  FROM hr.per_all_people_f ppf,
          hr.per_all_assignments_f asg,
        hr.per_assignment_status_types past,
          hr.hr_all_organization_units org,
       hr.hr_locations_all loc,
        hxc.hxc_timecard_summary hts,
        hr.per_person_type_usages_f ppu,
        gl.gl_code_combinations glc,
        hr.per_person_types ppt
WHERE ppu.effective_end_date BETWEEN ppf.effective_start_date AND ppf.effective_end_date
   AND ppu.effective_end_date BETWEEN asg.effective_start_date AND asg.effective_end_date
   AND (   (:v_start BETWEEN ppu.effective_start_date AND ppu.effective_end_date
        OR (:v_end BETWEEN ppu.effective_start_date AND ppu.effective_end_date
        OR (ppu.effective_start_date BETWEEN :v_start AND :v_end
   AND asg.primary_flag = 'Y'
   AND asg.assignment_type = 'E'
   AND asg.assignment_status_type_id = past.assignment_status_type_id
   AND asg.organization_id = org.organization_id
   AND asg.location_id = loc.location_id
   AND asg.default_code_comb_id = glc.code_combination_id
   AND ppf.person_id = ppu.person_id
   AND ppf.person_id = asg.person_id
   AND ppu.person_type_id = ppt.person_type_id
   AND ppt.user_person_type = 'Employee'
   AND ppf.person_id = hts.resource_id
   AND hts.start_time between :v_start and :v_end
   AND org.name = NVL(:v_department, org.name)
   AND loc.location_code = NVL(:v_location, loc.location_code)
   AND glc.code_combination_id = NVL(:v_gl_code_id, glc.code_combination_id)
   AND asg.supervisor_id = NVL(:v_sup_id, asg.supervisor_id)---------------------------------------------------------------
   AND ppf.person_id = NVL(:v_person_id, ppf.person_id)-------------------------------------------------------------------

Answer 1

user7726970 wrote:
Now I am more confused as we tried something similar yesterday and it did not help but your version makes it respond immediately. Thanks for this. Would you please explain a little why your version works where my version does not?
and decode(:v_sup_id,null,'x',asg.supervisor_id) = decode(:v_sup_id,null,'x',:v_sup_id)
and decode(:v_person_id,null,'x',ppf.person_id)  = decode(:v_person_id,null,'x',:v_person_id)that depends on your version. the example that i have posted is simply to verify if your variable is null then use a character 'x'. that is like where 'x' = 'x' which does not use any table column or simply does nothing at all. and if the variable is not null simply use the table column with the variable and i am assuming that the table column has an index on it will utilize it for performance.