RE: index hint ignored?

[Fink, Dan]

Title: Message

Gerald,

    Is veh_year a nullable column? If so, an index lookup may give you incorrect results (nulls are not indexed), so a full table scan will be used.

    Of course, is a full table scan a bad choice? Don't worry about the access path, find the plan that incurs the fewest I/Os and returns the quickest.

 

Dan Fink

-----Original Message-----
From: Cunningham, Gerald [mailto:[EMAIL PROTECTED]]
Sent: Friday, January 31, 2003 11:31 AM
To: Multiple recipients of list ORACLE-L
Subject: index hint ignored?

Hi there.

 

I have a non-unique index on a table, and I'm trying to force Oracle to use the index - but it always does a FTS. Why? (I've tried it with and without the alias)

 

 

SQL> set autotrace traceonly
SQL> SELECT /*+ INDEX(A,vehicle_veh_year_indx) */ DISTINCT veh_year
  2  FROM TIREADVISOR.vehicle A
  3  ORDER BY veh_year DESC;

 

20 rows selected.

 

Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=118 Card=20 Bytes=80)

   1    0   SORT (ORDER BY) (Cost=118 Card=20 Bytes=80)
   2    1     SORT (UNIQUE) (Cost=67 Card=20 Bytes=80)
   3    2       TABLE ACCESS (FULL) OF 'VEHICLE' (Cost=16 Card=19607 Bytes=78428)

 

 

===

 

 

select TABLE_NAME, INDEX_NAME, COLUMN_NAME, COLUMN_POSITION
from dba_ind_columns
where INDEX_OWNER = 'TIREADVISOR'
and TABLE_NAME = ('VEHICLE') order by 1,2,4,3

TABLE_NAME                     INDEX_NAME
------------------------------ ------------------------------
COLUMN_NAME          COLUMN_POSITION
-------------------- ---------------
VEHICLE                        VEHICLE_PK
VEH_ID                             1

 

VEHICLE                        VEHICLE_VEH_YEAR_INDX
VEH_YEAR                           1

 

 

 

Thanks for any help!

 

- Jerry