Bind variable code takes more time to complete?

Question

Hello, My database is oracle11g.
I have same plsql code and first one is without bind variable and second one is with bind variable. Usually, bind variable should take less time. But here
the bind variable takes more time than the regular code... Can any one please explain why?
SQL> alter system flush shared_pool;
System altered.
SQL> declare
2 cursor c1 is select * from emp where rownum < 50;
3 l_start NUMBER DEFAULT DBMS_UTILITY.GET_TIME;
4 v_cnt number;
5 begin
6 for i in c1 loop
7 SELECT count(*) into v_cnt
8 FROM rate
9 WHERE rate_id IN (SELECT rate_id
10 FROM ratedetail
11 WHERE benefit_id = i.benefit_id)
12 AND effective_date =
13 TO_DATE ('2011-01-23 00:00:00', 'yyyy-MM-dd HH24:MI:SS')
14 AND rate_type_id = 1;
15 end loop;
16 DBMS_OUTPUT.PUT_LINE('total minutes....'||ROUND(ROUND((DBMS_UTILITY.GET_TIME - l_start)/100, 2)
/60,3));
17 end;
18 /
total minutes.....06
PL/SQL procedure successfully completed.
SQL> alter system flush shared_pool;
System altered.
SQL>
SQL> declare
2 cursor c1 is select benefit_id from emp where rownum < 50;
3 l_start NUMBER DEFAULT DBMS_UTILITY.GET_TIME;
4 v_cnt number;
5 begin
6 for i in c1 loop
7 execute immediate 'SELECT count(*)
8 FROM rate
9 WHERE rate_id IN (SELECT rate_id
10 FROM ratedetail
11 WHERE benefit_id = :x)
12 AND effective_date = trunc(sysdate)-202
13 AND rate_type_id = 1'
14 into v_cnt using i.benefit_id;
15 end loop;
16 DBMS_OUTPUT.PUT_LINE('total minutes....'||ROUND(ROUND((DBMS_UTILITY.GET_TIME - l_start)/100, 2)
/60,3));
17 end;
18 /
total minutes.....061
PL/SQL procedure successfully completed.
SQL>

Answer 1

Shrinika wrote:
Thanks for the clarification.. Now i understand...
One final question on this thread before i close this thread....
My database is set to CURSOR_SHARING=FORCE for some reason. It seems somebody applied a "quick and dirty fix" to "database is slow" problem. BAD PRACTICE
My question is, when we use bind variable, does it parse the sql code every time? or does it reuse the execution plan?
In my database, it reuse the execution plan... Just checking... When we set CURSOR_SHARING=FORCE, it should generate the execution plan
for every unqiue sql code... Is that correct? Am i confusing?If by "parse" you mean a "hard parse" (which generates execution plan), then the answer is NO. As you observed, it reuses execution plan.
For e.g. with CURSOR_SHARING=FORCE setting, following SQLs
select employee_no, first_name, last_name from employees where dept_no = 10 ;and
select employee_no, first_name, last_name from employees where dept_no = 20 ;would tend to reuse the same execution plan since both of these will be rewritten by oracle (before execution) as
select employee_no, first_name, last_name from employees where dept_no = :SYS01 ;Hope this helps.
Edited by: user503699 on Aug 14, 2010 3:55 AM