We need to support consistent search behavior of our applications across different DB systems.
Generally search for objects by String fields in search pattern is expected to work like this:
customerId customerName
1 test
2 Test

Search for customer by customer.name = 'test' should return 1 AND 2 as results in all cases.
This is a problem on Oracle case sensitive systems however, where only 1 is returned.

To avoid this, Oracle allows to create function based indexes:
create index upper_name on customer ( upper(name));

Then query below should be used:
select customerId from customer where upper(name) = ?

Can it be implemented for all indexed columns by extending OracleDialect?

While was searching solution, found two other ways of case-insensitive search in Oracle.
1) For Oracle 10 it can be implemented by setting special
system environment variables: NLS_COMP and NLS_SORT
http://www.orafaq.com/node/91.
2) When using Criteria API call ignoreCase() method - it will generate lower function in sql when comparing strings.