APEX 4.1 APEX_UTIL.CLEAR_PAGE_CACHE Bug

Question

Hi,
I found the following issue in APEX 4.1. It's easiest described with an example:
Before going into a page process suppose P1_X = 'abc' in session state;
-- First page process (coming in P1_X = 'abc')
l_backup := :P1_X;
apex_util.clear_page_cache(:app_page_id);
:P1_X := l_backup;
-- Second page process (following the page process above)
-- This prints the value of P1_X to the screen
sys.htp.p(':P1_X: ' || nvl(:P1_X, 'null'));
-- Results:
-- APEX 4.0: (expected value)
:P1_X: abc
-- APEX 4.1 (incorrect)
:P1_X: nullIf I change +:P1_X := l_backup;+ line to apex_util.set_session_state('P1_X', l_backup); the output is:
-- Results (correct):
-- APEX 4.0:
:P1_X: abc
-- APEX 4.1
:P1_X: abcIf I change the +:P1_X := l_backup;+ line to +:P1_X := 'def';+ the output is:
-- Results (correct):
-- APEX 4.0:
:P1_X: def
-- APEX 4.1
:P1_X: defIt appears in 4.1 that any time a page item is set following a clear cache call (this issue also happens for clear_app_cache) and the page item value is the same as it was before the clear cache value (using a bind variable set) then its value is null in session state once the page process completes.
This was found in APEX version 4.1.1.00.23 and compared against 4.0.2.00.09
Martin
http://www.ClariFit.com
http://www.TalkApex.com
Edited by: Martin Giffy D'Souza on Oct 5, 2012 3:36 PM

Answer 1

Hi Martin,
thanks for reporting this. This change was introduced during a code reorg in 4.1.
The reason for the current behaviour is our dynamic code exec implementation:
1. create cursor and parse as user
2. for all bind variables:
3.      save session state value in local variable array
4.      bind local value in cursor
5. execute cursor
6. for all bind variables:
7.     if current bind value is different to local variable array value:
8.         save current value in session state Step 7 only detects a change if the bind variable value itself has been modified in the dynamic pl/sql block. I filed bug #14731783 to fix this, but we will probably ship it with the first patch set.
As a work-around, you should be able to use
l_backup := :P1_X;
apex_util.clear_page_cache(:app_page_id);
apex_util.set_session_state('P1_X', l_backup);
which does not rely on the dynamic code exec for writing back the original value of P1_X.
Regards,
Christian