Apex Collections and dates

Question

Apex Collections and Dates
I made an earlier posting today on the forum titled “‘ORA-01861: literal does not match format string’ error after my hosting company upgraded to Apex 3.2.” The issue relates to Apex collections and dates. Prior to the hosting company upgrading Apex 3.2 from 3.1 all was working OK. It seemed a reasonable assumption that the issue relates to the upgrade to 3.2. Having tested the code against another Apex 3.2 installation I am satisfied that the issue is not with Apex 3.2. That said, I am still getting the issue on the hosting site.
To demonstrate the issue to my hosting company and this forum, I put together a simple one page application that demonstrates the issue using the least amount of code.
I created a page with an ‘On Load – Before header” process that sets up an Apex Collection with a single value of ’20-FEB-2009’ in the c001 element as follows:
if apex_collection.collection_exists(p_collection_name=>'THEISSUE') then
apex_collection.delete_collection(p_collection_name=>'THEISSUE');
end if;
apex_collection.create_collection(p_collection_name => 'THEISSUE');
APEX_COLLECTION.ADD_MEMBER(
p_collection_name => 'THEISSUE',
p_c001 => '20-FEB-2009');
I added an SQL REPORT region to the page which uses the Apex Collection as follows:
select to_date(c001,'DD-MON-YYYY') testdate
from apex_collections
where collection_name='THEISSUE'
and to_date('20-FEB-2009','DD-MON-YYYY')
= to_date(c001,'DD-MON-YYYY')
When the page is run I get the ‘ORA-01861: literal does not match format string’ error.
If I remove the following from the SQL Report Region:
and to_date('20-FEB-2009','DD-MON-YYYY')
= to_date(c001,'DD-MON-YYYY')
and run the page, the date is displayed OK, i.e., c001 is converted to a date OK. This made me wonder whether it does not like the line to_date('20-FEB-2009','DD-MON-YYYY')? So I changed the where code for the report to :
and to_date(c001,'DD-MON-YYYY')
= to_date(c001,'DD-MON-YYYY')
i.e., convert c001 to a date and compare it to itself. The rationale being that if the c001 converts to a date OK, then comparing c001 converted to a date with itself should not give an error. It did it gave the same error ‘ORA-01861’
It would seem on my hosting site since the upgrade, that Apex and Oracle have problems with Apex Collection elements being converted to dates as part of the where clause.
Now my understating of Oracle Apex collections in simple terms is that all Apex collections are held in a single Oracle table managed by a series of Apex functions. Given that all Apex collections are in the same table, could the issue be with the Oracle database when it is creating its execution plan for the query? Could Oracle be including the value of c001 from other collections (i.e., when c001 is not in a date format ) in the initial stages of its execution plan?
I hope the above make sense and thanks in advance.
Ian

Answer 1

Scott,
I believe I have found the answer the statistics on WWV_FLOW_COLLECTIONS$ and WWV_FLOW_COLLECTION_MEMBERS$. are out of date and Oracle is doing a full table scan instead of using the indices to select only the c001 columns that belong to the given collection_id. If I change my simple example to store the date value in c050 it works ok. (In all probability this will be the only collection on the hosted database to use c050).
I have asked the hosting company to gather stats on all the apex tables.
Thanks for your help
Ian