Performance of SQL-Statements in Reports

Question

Hi
I have a very complex SQL-Statement in a Region-Report with Items in the where-clause:
select ....
where  idt_1 like :P1_IDT
and    idt_2 like :P1_IDT2
...it generates 100 Million records in the Temp Tablespace and produce either a timeout or an error-message that the Temp-Tablespace is not big enough.
If I replace the Items with real values it runs in a few seconds in the SQL-Workshop.
select ....
where  idt_1 like 10
and    idt_2 like 11
...If I use the Region-Type based "PL/SQL Function Body returning SQL Statement" and generate the Statment like this:
v_statment:= 'select ... where idt_1 like ' || :P1_IDT;
return v_statment;it runs in a few seconds too.
Any explanations?
Regards, Juergen

Answer 1

Jürgen,
John's recommendation is sound. Your last two examples ultimately use literal values in your query statement (that is, the query optimizer can use these values to determine the optimal query plan). The query plans for the last two queries may be entirely different than what was generated for your first query.
Additionally, if the selectivity of your first query shifted dramatically across subsequent executions, the query plan initially generated may not be suitable again.
Examining the tkprof output should elucidate all of this.
Joel