Hong Su from Inside the Oracle Optimizer:
The Join Factorization transformation was introduced in Oracle 11g Release 2 and applies to UNION ALL queries. Join factorization is a cost-based transformation. It can factorize common computations from branches in a UNION ALL query which can lead to huge performance improvement.
Yet another reason to upgrade to 11gR2.
Filed in Links
on 25 Feb 11 | Tags: performance