11g Partitioning Enhancements Oracle 11g New Features Tips by Burleson Consulting June 27, 2008

Oracle 11g SQL New Features Tips

Partitioning in Oracle is instrumental in supporting large databases and data warehousing requirements. While this feature dramatically improves manageability, performance, and availability, Oracle relies on the Remote DBA to manually define each partition.  In data warehousing environments, the creation of new partitions is a monotonous but necessary element of scheduled maintenance.  Oracle 11g has introduced a new partitioning feature, called Interval Partitioning, that allows Oracle to automatically create new partitions as data is inserted.  While there are certain limitations to using interval partitioning, it has proven to be a very effective feature when used in the appropriate context.  This section will demonstrate how to use this feature, discuss its limitations, and provide recommendations for making the most of this exciting enhancement. 

Partitioning is the division of tables, indexes, or index-organized tables into smaller pieces.  These smaller pieces are called partitions which can be managed and accessed independently.  This concept is commonly characterized as a divide-and-conquer approach to managing large tables and indexes.  When defining a partitioned table, one or more columns are used as keys to match the row into the appropriate partition. Data loads in partitioned tables will fail if one or more records cannot be matched to an existing partition. 

Interval partitioning is an enhancement to range partitioning.  Range partitioning allows an object to be partitioned by a specified range on the partitioning key.  For example, if a table was used to store sales data, it might be range partitioned by a DATE column, with each month in a different partition.  Therefore, every month a new partition would need to be defined in order to store rows for that month.  If a row was inserted for a new month before a partition was defined for that month, the following error would result:

ORA-14400: inserted partition key does not map to any partition 

If this situation occurs, data loading will fail until the new partitions are created.  This can cause serious problems in larger data warehouses where complex reporting has many steps and dependencies in a batch process.  Mission critical reports might be delayed or incorrect due to this problem. 

Interval partitioning can simplify the manageability by automatically creating the new partitions as needed by the data.  Interval partitioning is enabled in the table’s definition by defining one or more range partitions and including a specified interval.  For example, consider the following table:

create table
pos_data (
   start_date        DATE,
   store_id          NUMBER,
   inventory_id      NUMBER(6),
   qty_sold          NUMBER(3),
)
PARTITION BY RANGE (start_date)
INTERVAL(NUMTOYMINTERVAL(1, 'MONTH'))
( 
   PARTITION pos_data_p2 VALUES LESS THAN (TO_DATE('1-7-2007', 'DD-MM-YYYY')),
   PARTITION pos_data_p3 VALUES LESS THAN (TO_DATE('1-8-2007', 'DD-MM-YYYY'))
); 

Here, two partitions have been defined and an interval of one month has been specified.  If data is loaded into this table with a later date than the greatest defined partition, Oracle will automatically create a new partition for the new month.  In the table above, the greatest defined interval is between July 1, 2007 and August 1, 2007.  Inserting a row that has a date later than August 1, 2007 would raise an error with normal range partitioning.  However, with interval partitioning, Oracle determines the high value of the defined range partitions, called the transition point, and creates new partitions for data that is beyond that high value.

insert into pos_data (start_date, store_id, inventory_id, qty_sold)
values ( '15-AUG-07', 1, 1, 1);

SELECT
   TABLE_NAME,
   PARTITION_NAME,
   PARTITION_POSITION,
   HIGH_VALUE
FROM
   Remote DBA_TAB_PARTITIONS
WHERE
   TABLE_NAME='POS_DATA'
ORDER BY
   PARTITION_NAME;

PARTITION_NAME    HIGH_VALUE 

POS_DATA_P0       TO_DATE(' 2007-07-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN')

POS_DATA_P1       TO_DATE(' 2007-08-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN')

SYS_P81    TO_DATE(' 2007-09-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN')

Notice that a system generated partition named SYS_P81 has been created upon inserting a row with a partition key greater than the transition point.  Oracle will manage the creation of new partitions for any value beyond the high value.  Therefore, the values do not need to be inserted in sequence.

 

This is an excerpt from the new book Oracle 11g New Features: Expert Guide to the Important New Features by John Garmany, Steve Karam, Lutz Hartmann, V. J. Jain, Brian Carr. You can buy it direct from the publisher for 30% off.