Prompt on DATE forces FULL TABLE SCAN

Question

When using a prompt on a datetime field OBIEE sends a SQL to the Database with the TIMESTAMP COMMAND.
Due to Timestamp the Oracle database does a Full Table Scan. The field ATIST is a date with time on the physical database.
By Default ATIST was configured as TIMESTAMP in the rpd physical layer. The SQL request is sent to a Oracle 10 Database.
That is the query sent to the database:
-------------------- Sending query to database named PlantControl1 (id: <<10167>>):
select distinct T1471.ATIST as c1,
T1471.GUTMENGEMELD2 as c2
from
AGRUECK T1471 /* Fact_ARBEITSGANGMELDUNGEN */
where ( T1471.ATIST = TIMESTAMP '2005-04-01 13:48:05' )
order by c1, c2
The result takes more than half a minute to appear.
Because BIEE is using "TIMESTAMP" , the database performs a full table scan instead of using the index.
By using TO_DATE instead of timestamp the result appears after a second.
select distinct T1471.ATIST, T1471.GUTMENGEMELD2 as c2
from
AGRUECK T1471 /* Fact_ARBEITSGANGMELDUNGEN */
where ( T1471.ATIST = to_date('2005.04.01 13:48:05', 'yyyy.mm.dd hh24:mi:ss') );
Is there any way resolving the issue?
PS:When the field ATIST is configured as date at the physical layer the SQL performs well is it uses the command "to_date" instead of "timestamp". But this cuts the time of the date, When it is configured as DATETIME, OBIEE uses TIMESTAMP again.
What I need is a working date + time field.
Anybody has encountered a similiar problem?

Answer 1

To be honest I haven't come across many scenarios where the Time has been important. Most of our reporting stops at Day level.
What is the real world business question being asked here that requires DayTime?
Incidentally if you change your datatype on the base table you will see it works fine.
CREATE TABLE daytime( daytime TIMESTAMP );
CREATE UNIQUE INDEX dt ON daytime  (daytime)
SQL> set autotrace traceonly
SQL> SELECT * FROM daytime
  2  WHERE daytime = TIMESTAMP '2007-04-01 13:00:45';
no rows selected
Execution Plan
Plan hash value: 3985400340
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |      |     1 |    13 |     1   (0)| 00:00:01 |
|*  1 |  INDEX UNIQUE SCAN| DT   |     1 |    13 |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   1 - access("DAYTIME"=TIMESTAMP' 2007-04-01 13:00:45.000000000')
Statistics
          1  recursive calls
          0  db block gets
          1  consistent gets
          0  physical reads
          0  redo size
        242  bytes sent via SQL*Net to client
        362  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          0  rows processed
SQL>However if its a date it would appear to do some internal function call which I guess is the source of the problem ...
| Id  | Operation         | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |         |     1 |     9 |     2   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| DAYTIME |     1 |     9 |     2   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   1 - filter(INTERNAL_FUNCTION("DAYTIME")=TIMESTAMP' 2007-04-01
              13:00:45.000000000')