Return value from database function taking a lot more time than the query

Question

Hi guys,
I have a Query that does a call to a database function. The function takes in a few parameters and returns a Date. Now, the query within the function takes barely .05 seconds. However, doing a select get_join_dates from dual is taking almost 6 seconds for each call.
Here is the Query:
select s.student_id, s.student_name, s.organization_code
from   student s
where  s.student_id = :p_student_id
and    s.student_enrollment_date = get_join_dates( :p_year,
                                                   :p_month,
                                                   :p_student_id,
                                                   s.organization_code );And here is the database function. The select inside this function barely takes 0.05 seconds per call. This function gets called 3 times in my case as there are 3 records in the org_body table for this student.
create or replace function
get_join_dates( p_yyyy in org_body.fiscal_yyyy%type,
                       p_month in  org_body.fiscal_mm%type,
                       p_student_id in student.student_id%type,
                       p_organization_code in org_body.organization_code%type) return date as
    t_enrollment_date  date;
    cursor cur_latest_enrollment_date is
      select max(enrollment_date)
      from   org_body
      where  fiscal_yyyy = p_yyyy
      and    fiscal_mm = p_month
      and    student_id = p_student_id
      and    organization_code = p_organization_code;
  BEGIN
    open cur_latest_enrollment_date ;
    fetch cur_latest_enrollment_date into t_enrollment_date;
    close cur_latest_enrollment_date ;
    return t_enrollment_date;
  exception
    when others then
      null;
end;owever, when I run the following statement below, it takes close to 6 seconds to retrieve a record. In turn, my Query is becoming really slow and taking almost 35 seconds. Imagine that with more records.
select get_join_dates( 2010, '01', '2167543', 'PSYCH01' ) from dual;If I run my query with this condition below, it takes 0.5 seconds.
select s.student_id, s.student_name, s.organization_code
from   student s
where  s.student_id = :p_student_id
and      s.student_enrollment_date = '01-JAN-10'Any ideas would be greatly appreciated.

Answer 1

Any reason why you are doing this with the stored function?
You could just do this with SQL. Embed the query in the function as a subquery in your initial query from STUDENT.
select s.student_id, s.student_name, s.organization_code
from   student s
where  s.student_id = :p_student_id
and    s.student_enrollment_date =
(select max(enrollment_date)
      from   org_body
      where  fiscal_yyyy = :p_year
      and    fiscal_mm = :p_month
      and    student_id = s.student_id
      and    organization_code = s.organization_code);Why your function is not performing: I cannot say that with the information you have provided.
Maybe sqltrace a call and see what the reason is.