Functional indexes ignored in sql plan (12.1.0.2 - FORCE)

Hi,

We had a 12.1.0.2.

cursor_sharing=FORCE

The following query (from T24 banking application):

select t.recid from ftn1_account t where NVL(NUMCAST(EXTRACTVALUES(t.xmlrecord,'/row/c2')),0)=3439;

Which was using the corresponding functional index based on:  NVL(NUMCAST(EXTRACTVALUE(XMLRECORD,'/row/c2')),0)

From now, the same query, just full scans the table.

Exec time is 17m.

Workaround:

cursor_sharing=EXACT

Functionnal index is used.

Exec time back to the hundredth of  18 second.

But because the application's queries are not binded, the cost in term of CPU is high (but we have plenty of them...).