Range Partitioniung problems

Question

Hi All,
I created a table as follows and wanted to test how a partition by range works.
CREATE TABLE test_partition
( emp_id NUMBER,
  time_period_from DATE,
  time_period_to DATE,
  time_period_desc VARCHAR(10),
  empfigure NUMBER, CONSTRAINT pk_test PRIMARY KEY (emp_id,time_period_from,time_period_to,time_period_desc)
  PARTITION BY RANGE(time_period_from)
  (PARTITION jan2009 VALUES LESS THAN ('01-Feb-2009') TABLESPACE tbl1,
   PARTITION feb2009 VALUES LESS THAN ('01-Mar-2009') TABLESPACE tbl1,
   PARTITION oth VALUES LESS THAN (MAXVALUE) TABLESPACE tbl1
   )I inserted the data as follows:
1000    2/1/2009    2/28/2009    'Month'    6000
1000    2/15/2009    2/15/2009    'Day'    4000
1000    2/16/2009    2/16/2009    'Day'    2000
1000    3/1/2009    3/31/2009    'Month'    10000
1000    3/15/2009    3/15/2009    'Day'    5000
1000    3/16/2009    3/16/2009    'Day'    5000
2000    2/1/2009    2/28/2009    'Month'    6000
2000    2/15/2009    2/15/2009    'Day'    4000
2000    2/16/2009    2/16/2009    'Day'    2000
2000    3/1/2009    3/31/2009    'Month'    10000
2000    3/15/2009    3/15/2009    'Day'    5000
2000    3/16/2009    3/16/2009    'Day'    5000Following are my Questions:
1)     How does partition help in this case when I do a select query,
Select * from test_partition where to_date(time_period_from) > ’01-Feb-2009’
and to_date(time_period_to) < ’01-Mar-2009’??
I could see from the plan table that all the partitions are scanned…
Then what is the use of partitions exactly?
2)     Is it that I need to force the user to use the partition explicitly in the select queries? If that is the case when there is an application where a user can select a date range in the front-end, then how do I dynamically determine which partition to use? Any samples for that?
3)     The most worrying part:
SELECT table_name, partition_name,num_rows
FROM user_tab_partitions
WHERE lower(table_name) = 'test_partition';
TABLE_NAME             PARTITION_NAME     NUM_ROWS
'TEST_PARTITION'     'FEB2009'     
'TEST_PARTITION'     'JAN2009'     
'TEST_PARTITION'     'OTH'    There are no rows inserted in partitions??? (Since num_rows is null in each case)

Answer 1

Ok just got into the concept of partitions.........
So this is what i did for the testing.... Still not able to get the concpet
(1)
/* Formatted on 2008/08/15 12:40 (Formatter Plus v4.8.8) */
CREATE TABLE test_partition
( emp_id VARCHAR2(30),
  time_period_from DATE,
  time_period_to DATE,
  time_period_desc VARCHAR(10),
  empfig NUMBER
  PARTITION BY RANGE(time_period_from)
  (PARTITION jan2008 VALUES LESS THAN( TO_DATE('01-Feb-2008','dd-mon-yyyy')) TABLESPACE esmdata,
   PARTITION feb2008 VALUES LESS THAN (TO_DATE('01-Mar-2008','dd-mon-yyyy') )TABLESPACE esmdata,
   PARTITION mar2008 VALUES LESS THAN (TO_DATE('01-Apr-2008','dd-mon-yyyy') )TABLESPACE esmdata,
   PARTITION oth VALUES LESS THAN (MAXVALUE) TABLESPACE esmdata
(2)
INSERT /*+ APPEND */ INTO  test_partition
   SELECT eid,
          time_period_from,
          time_period_to,
          time_period_desc,
          nof_disp_complete
     FROM emp_tab
    WHERE time_period_from BETWEEN to_date('01-jan-2008','dd-mon-yyyy') AND to_date('30-Apr-2008','dd-mon-yyyy')
(3)
analyze table TEST_PARTITION compute statistics;
(4)
SELECT *
    FROM test_partition
   WHERE time_period_from = '01-Mar-2008'
ORDER BY emp_id,
         time_period_from
toad  plan
Time     Plan
     SELECT STATEMENT               
3           3 PARTITION RANGE SINGLEPartition #: 1  Partitions accessed #3          
2                2 SORT ORDER BY     
1                     1 TABLE ACCESS FULL TABLEPartition #: 3  Partitions accessed #3
(5)
SELECT *
    FROM test_partition
   WHERE trunc(time_period_from) = '01-Mar-2008'
ORDER BY emp_id,
         time_period_from
toad plan
Time     Plan
     SELECT STATEMENT               
3           3 SORT ORDER BY          
2                2 PARTITION RANGE ALLPartition #: 2  Partitions accessed #1 - #4     
1                     1 TABLE ACCESS FULL TABLEPartition #: 2  Partitions accessed #1 - #4Not sure why all the partitions are scanned in the last case........... eventhough the data has been partitioned according to the date.....
Can you folks help me... Because I have queries which always has to go to the first of the months and select one months worth of data and hence using trunc('MM') and also last_day() fucntion in oracle..... Just wanted to check how to use the partitions in this case....
Also just to mention , there are nearly 1 million record in this table
regds,
Saff
Message was edited by:
saffron