Please help me optimize this

Question

1. This code fragment:
declare
procedure t(ent in varchar)
is
begin
for reg in (
select
/*+nocache*/
opds_psap_numero,
min(opds_data_inicio_tarde) as opds_data_inicio_tarde
from operacoes_diagrama_sap, projeto_sap
where
opds_psap_numero = psap_numero and
psap_pep like ent
group by
opds_psap_numero
) loop
dbms_output.put_line('just teste');
end loop;
end;
begin
t('PR42E-075001%');
end;
Execution Time
***SCRIPT START 29-mar-2007 17:33:25 ***
***SCRIPT END 29-mar-2007 17:35:13 ***
Time = 2 minutes (aprox)
==============================================
2. But this code fragment (the same as before but with static sql):
declare
procedure t(ent in varchar)
is
begin
for reg in (
select
/*+nocache*/
opds_psap_numero,
min(opds_data_inicio_tarde) as opds_data_inicio_tarde
from operacoes_diagrama_sap, projeto_sap
where
opds_psap_numero = psap_numero and
psap_pep like 'PR42E-075001%'
group by
opds_psap_numero
) loop
dbms_output.put_line('just teste');
end loop;
end;
begin
t('PR42E-075001%');
end;
Execution Time
***SCRIPT START : 29-mar-2007 17:39:29***
***SCRIPT END 29-mar-2007 17:39:30***
Time 1 sec
================================================
I need the code of the first example (I must pass an 'in" parameter to the procedure), but with performance of the second.
This query runs very fast when posted in sqlnavigator.
it returns approx 1000 lines and i have an index at projeto_sap.psap_pep field
What am i doing wrong?
Please if you dont understand let me know. English is not my first language. From hot Brazil hehe

Answer 1

Your second fragment has a string literal 'PR42E-075001%' for the LIKE operator in your WHERE clause. The first fragment uses a PL/SQL parameter, effectively a bind variable.
The optimizer can choose the index for the second fragment because it knows the index will be effective. But the first fragment could have any value for the variable. The optimizer chooses a path that is best for "any value" AND YOU WIND UP WITH A PLAN THAT ...
Hmm, I hit the caps lock by accident there, but it seems strangely appropriate.
Anyway, you can try adding a hint to your query:
/*+ nocache index( projeto_sap index_name */