Jonathan Lewis has been working in the information technology industry for nearly 25 years, and has been using the Oracle relational database management system for more than 20. For the past 16 years, he has worked as a freelance consultant, often spending only one or two days at a time with any client to address critical performance problems. He also advises on design and implementation problems, and on how to make best use of the most appropriate Oracle features for a given project. Jonathan is also renowned throughout the world for his tutorials and seminars about the Oracle database engine and how to make best use of it. Having visited 42 countries at last count, his exceptional ability has earned him an O1 visa from the United States, allowing him to do consultancy and lecture work there. Jonathan has written two books about Oracle (Practical Oracle8i, Addison-Wesley, 2000; Cost-Based Oracle Fundamentals, Apress, 2005), and has contributed to two others (Oracle Insights, Apress, 2004; Oracle Database 10g New Features, Oracle Press, 2004). He also writes regularly for the UKOUG magazine, and occasionally for other publications around the world. In the limited amount of time he has leftover, Jonathan also publishes high-tech Oracle articles on his blog at jonathanlewis.wordpress.com.
Cost-Based Oracle Fundamentalsby Jonathan Lewis, Thomas Kyte
The question, "Why isnt Oracle using my index?" must be one of the most popular (or perhaps unpopular) questions ever asked on the Oracle help forums. Youve picked exactly the right columns, youve got them in the ideal order, youve computed statistics, youve checked for null columnsand the optimizer flatly refuses to use your
The question, "Why isnt Oracle using my index?" must be one of the most popular (or perhaps unpopular) questions ever asked on the Oracle help forums. Youve picked exactly the right columns, youve got them in the ideal order, youve computed statistics, youve checked for null columnsand the optimizer flatly refuses to use your index unless you hint it. What could possibly be going wrong?
If youve suffered the frustration of watching the optimizer do something completely bizarre when the best execution plan is totally obvious, or spent hours or days trying to make the optimizer do what you want it to do, then this is the book you need. Youll come to know how the optimizer thinks, understand why it makes mistakes, and recognize the data patterns that make it go awry. With this information at your fingertips, you will save an enormous amount of time on designing and trouble-shooting your SQL.
The cost-based optimizer is simply a piece of code that contains a model of how Oracle databases work. By applying this model to the statistics about your data, the optimizer tries to efficiently convert your query into an executable plan. Unfortunately, the model can't be perfect, your statistics can't be perfect, and the resulting execution plan may be far from perfect.
In Cost-Based Oracle Fundamentals, the first book in a series of three, Jonathan Lewisone of the foremost authorities in this fielddescribes the most commonly used parts of the model, what the optimizer does with your statistics, and why things go wrong. With this information, youll be in a position to fix entire problem areas, not just single SQL statements, by adjusting the model or creating more truthful statistics.
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