Partition Pruning和Partition-Wise Joins

Partition Pruning

Partition pruning is an essential performance feature for data warehouses. In partition pruning, the optimizer analyzes FROM and WHERE clauses in SQL statements to eliminate unneeded partitions when building the partition access list. As a result, Oracle Database performs operations only on those partitions that are relevant to the SQL statement.

Partition pruning dramatically reduces the amount of data retrieved from disk and shortens processing time, thus improving query performance and optimizing resource utilization.

Partition-wise joins reduce query response time by minimizing the amount of data exchanged among parallel execution servers when joins execute in parallel. This significantly reduces response time and improves the use of both CPU and memory resources.

Partition-wise joins can be full or partial. Oracle Database decides which type of join to use.

Benefits of Partition-Wise Joins

Partition-wise joins offer benefits described in the following topics:

• Reduction of Communications Overhead

• Reduction of Memory Requirements

https://docs.oracle.com/cd/E11882_01/server.112/e25523/part_warehouse.htm