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ORACLE8i- P27: We want information information.” Possibly you recognize these words as the primary interest of a somewhat clandestine group, and as told by a character called Number 2 to Patrick McGoohan’s character Number 6 (in the old TV show The Prisoner). Indeed, in this day, information is king, and the speedy, accurate, and reliable retrieval of this information is paramount. | 1040 CHAPTER 24 DATABASE PARTITIONING Purging data from unused partitions Backup and restoration of unused partitions Reorganization Index building Partition-Wise Joins A partition-wise join is a large join operation divided into smaller parts and executed in parallel. The results of the smaller joins are then brought back together as if the separation had never taken place. This utilizes Oracle s capabilities of both parallel processing and partitioning. For a partition-wise join to occur the following conditions must exist Both tables in the join statement must be equipartitioned. Either the tables or the indexes in the join operation must use the same partitioning method. Both tables or indexes must have the same partitioning columns. Both tables or indexes must have the same number of partitions. In range partitioning the same partition bounds are required. In composite partitioning only one of the tables need be equipartitioned. Example of a Partition-Wise Join Figure 24.1 represents four equipartitioned objects tables and indexes in a project task relationship. The PROJECTS and TASKS tables are divided into two partitions each by project number. The indexes have the same partitioning bounds. Specifically PROJECTS is a table with two partitions range-partitioned on column PRO-JECT_NO. The first partition contains project numbers up to 200000. The second partition contains project numbers up to 400000. PROJECTS_N1 is an index on column PROJECT_NO of the PROJECTS table. Both the table and index are range-partitioned on column PROJECT_NO into two partitions which have the same partition bounds as the PROJECTS table s partitions. These are the elements that begin to develop the requirements listed just above. Please purchase PDF Split-Mewon www.verypdfecom to removfibihis watermark. PARTITION-WISE JOINS 1041 FIGURE 24.1 Equipartitioned tables and indexes TASKS is a table with two partitions range-partitioned on column PROJECT_NO this is the same as the PROJECTS .
