Using TRUNC function on partitioned column

Question

Hi All,
I have a table as follows:
STEP1
CREATE TABLE TEST_PARTITION
EMP_ID VARCHAR2(10 BYTE),
CREATE_DT DATE,
EMP_RGN_NM VARCHAR2(2 BYTE),
DSPTCH_CNT NUMBER
PARTITION BY RANGE (CREATE_DT)
SUBPARTITION BY LIST(EMP_RGN_NM)
SUBPARTITION TEMPLATE(
SUBPARTITION RGN_E VALUES ('E') ,
SUBPARTITION RGN_MW VALUES ('MW') ,
SUBPARTITION RGN_SW VALUES ('SW') ,
SUBPARTITION RGN_W VALUES ('W') ,
SUBPARTITION RGN_SE VALUES ('SE')
PARTITION aug2008 VALUES LESS THAN (TO_DATE('01-Sep-2008', 'DD-MON-YYYY')),
PARTITION sep2008 VALUES LESS THAN (TO_DATE('01-Oct-2008', 'DD-MON-YYYY')),
PARTITION oth VALUES LESS THAN (MAXVALUE)
ENABLE ROW MOVEMENT;
STEP 2
insert into TEST_PARTITION values(1000,TO_DATE('01-Aug-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',10)
insert into TEST_PARTITION values(1000,TO_DATE('02-Aug-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',20);
insert into TEST_PARTITION values(1000,TO_DATE('03-Aug-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',0);
insert into TEST_PARTITION values(1000,TO_DATE('01-sep-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',10);
insert into TEST_PARTITION values(1000,TO_DATE('02-sep-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',10);
insert into TEST_PARTITION values(1000,TO_DATE('01-Oct-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',10);
insert into TEST_PARTITION values(1001,TO_DATE('01-Aug-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',1);
insert into TEST_PARTITION values(1001,TO_DATE('02-Aug-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',2);
insert into TEST_PARTITION values(1001,TO_DATE('03-Aug-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',0);
insert into TEST_PARTITION values(1001,TO_DATE('01-sep-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',10);
insert into TEST_PARTITION values(1001,TO_DATE('02-sep-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',5);
insert into TEST_PARTITION values(1001,TO_DATE('01-Oct-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',10);
insert into TEST_PARTITION values(1001,TO_DATE('02-Oct-2008 12:02:02', 'DD-MON-YYYY HH:MI:SS'),'SE',10);
STEP 3
I need to get all the dispatches on 1st of August and hence issue the statement as follows:
select * from test_partition where TRUNC(CREATE_DT)='01-Aug-2008' and EMP_RGN_NM = 'SE'
Using a function over the partitioned column, will it avaoid partition pruning? I mean will it scan all the partitiones instead of going to specific partition?
I need this urgently since we are having a discussion on this in few minutes from now.
Thanks so much
Saff

Answer 1

What about a function based index ?
SQL> select * from test_partition where TRUNC(CREATE_DT)='01-Aug-2008' and EMP_RGN_NM = 'SE';
Execution Plan
| Id  | Operation              | Name           | Rows  | Bytes | Cost (%CPU)| Pstart| Pstop |
|   0 | SELECT STATEMENT       |                |     1 |    32 |     4   (0)|       |       |
|   1 |  PARTITION RANGE ALL   |                |     1 |    32 |     4   (0)|     1 |     3 |
|   2 |   PARTITION LIST SINGLE|                |     1 |    32 |     4   (0)|   KEY |   KEY |
|   3 |    TABLE ACCESS FULL   | TEST_PARTITION |     1 |    32 |     4   (0)|   KEY |   KEY |
Note
   - 'PLAN_TABLE' is old version
SQL> create index idx on test_partition (TRUNC(CREATE_DT));
Index created.
SQL> select * from test_partition where TRUNC(CREATE_DT)='01-Aug-2008' and EMP_RGN_NM = 'SE';
Execution Plan
| Id  | Operation                          | Name           | Rows  | Bytes | Cost (%CPU)| Pstart| Pstop |
|   0 | SELECT STATEMENT                   |                |     1 |    32 |     2   (0)|       |       |
|   1 |  TABLE ACCESS BY GLOBAL INDEX ROWID| TEST_PARTITION |     1 |    32 |     2   (0)| ROWID | ROWID |
|   2 |   INDEX RANGE SCAN                 | IDX            |     1 |       |     1   (0)|       |       |
Note
   - 'PLAN_TABLE' is old version
I need this urgently since we are having a discussion on this in few minutes from now.It is not our problem, but yours.
Nicolas.