SQL report performance problem

Question

I have a SQL classic report in Apex 4.0.2 and database 11.2.0.2.0 with a performance problem.
The report is based on a PL/SQL function returning a query. The query is based on a view and pl/sql functions. The Apex parsing schema has select grant on the view only, not the underlying objects.
The generated query runs in 1-2 sec in sqlplus (logged in as the Apex parsing schema user), but takes many minutes in Apex. I have found, by monitoring the database sessions via TOAD, that the explain plan in the Apex and sqlplus sessions are very different.
The summary:
In sqlplus SELECT STATEMENT ALL_ROWS Cost: 3,695                                                                            
In Apex SELECT STATEMENT ALL_ROWS Cost: 3,108,551                                                        
What could be the cause of this?
I found a blog and Metalink note about different explain plans for different users. They suggested to set optimizer_secure_view_merging='FALSE', but that didn't help.

Answer 1

Hmmm, it runs fast again in SQL Workshop. I didn't expect that, because both the application and SQL Workshop use SYS.DBMS_SYS_SQL to parse the query.
Only the explain plan doesn't show anything.
To add: I changed the report source to the query the pl/sql function would generate, so the selects are the same in SQL Workshop and in the application. Still in the application it's horribly slow.
So, Apex does do something different in the application compared to SQL Workshop.
Edited by: InoL on Aug 5, 2011 4:50 PM