Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

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CHAPTER 13 ■ PARTITIONING
Figure 13-4. Range-hash composite partition example
So, composite partitioning gives you the ability to break up your data by range and, when
a given range is considered too large or further partition elimination could be useful, to break
it up further by hash or list. It is interesting to note that each range partition need not have the
same number of subpartitions; for example, suppose you were range partitioning on a date
column in support of data purging (to remove all old data rapidly and easily). In the year 2004,
you had equal amounts of data in “odd” code numbers in the CODE_KEY_COLUMN and in “even”
code numbers. But in 2005, you knew the number of records associated with the odd code
number was more than double, and you wanted to have more subpartitions for the odd code
values. You can achieve that rather easily just by defining more subpartitions:
ops$tkyte@ORA10G> CREATE TABLE composite_range_list_example
2 ( range_key_column date,
3 code_key_column int,
4 data varchar2(20)
5 )
6 PARTITION BY RANGE (range_key_column)
7 subpartition by list(code_key_column)
8 (
9 PARTITION part_1
10 VALUES LESS THAN(to_date('01/01/2005','dd/mm/yyyy'))
11 (subpartition part_1_sub_1 values( 1, 3, 5, 7 ),
12 subpartition part_1_sub_2 values( 2, 4, 6, 8 )