The cost-based optimizer optimizes
execution plans for star schema queries, heavily used in data warehousing, while the
rule-based optimizer has not been enhanced to deal effectively with these types of
queries or leverage many other such business intelligence query features.
Oracle Corporation was quite frank about its intention to make the cost-based optimizer
the optimizer for the Oracle database through a period of years when both
optimizer types were supported. In fact, since Oracle Database 10g, the rule-based
optimizer is no longer supported.
We will remind youof one fact of database design at this point. As good as the costbased
optimizer is today, it is not a magic potion that remedies problems brought on
by a poor database and application design or a badly selected hardware and storage
platform. When performance problems occur today, they are most often due to bad
design and deployment choices.
116 | Chapter 4: Oracle Data Structures
Accepting the Verdict of the Optimizer
Some of you may doubt the effectiveness of Oracle query optimization if you are on an
old Oracle database release, especially prior to Oracle Database 10g where tuning often
required running scripts.
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