Zend_Db_Adapater_Oracle and "UPPER" problem

Following problem:

Table with 1000 000 Records

If i use the following query with Zend_Db_Adapter_Oracle:

SELECT COUNT(*) FROM XYZ WHERE (UPPER(ATTRIBUTE)='XXX') AND UPPER(OBJECT)='XX'

I takes a round 15sec.

If i use OCI_CONNECT (native php) i takes 3 seconds. If i remove (UPPER) from the query with the Zend Adapater its altough 3 seconds.

Does somone has an idea how to user upper and altough run an fast query? :-)

use a function based index: http://use-the-index-luke.com/sql/where-clause/functions/case-insensitive-search

however, that doesn't explain why it works better with a different connection type, sure you issue the same statement twice? or maybe caching effects?