Performance Tuning :: Nested Select / Instead Of Trigger And Views - No Index Used?

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi
PL/SQL Release 10.2.0.4.0 - Production
CORE 10.2.0.4.0 Production
TNS for Solaris: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - Production

5 rows selected.

I have a problem with views and nested selects which I cannot explain. Here is a trimed down version of the research I have done. notice the following:

1) all code is executed from the same user CDRNORMALCODE. this user has all views and procedural code
2) all data is owned by a different user CDRDATA. This user has no views and no code.

My problem is this:

If I reference the table directly with a delete statement that uses a nested select (i.e. IN clause with select), the index I expect and want is used.But if I execute the same delete but reference even the most simple of views (select * from <table>) instead of the table itself, then a full table scan is done of the table.

Here is an execute against the table directly (owned by cdrdata). Notice the reference to the table in the table schema on line 3. Also please notice INDEX RANGE SCAN BSNSS_CLSS_CASE_RULE_FK1 at the bottom of the plan.

SQL> show user
USER is "CDRNORMALCODE"
SQL>
SQL> explain plan for
2 delete

[code]...

OK, here is an update. The views I am useing normally have instead of triggers on them. If I remove the instead of trigger the problem looks like it goes away, when I put the trigger back the problem comes back.But why would an instead-of-trigger change the query plan for a view?

SQL> DELETE FROM PLAN_TABLE;

5 rows deleted.

SQL> explain plan for
2 delete
3 from BSNSS_CLSS_MNR_CASE_RULE_SV

[code]...