CHAPTER 9

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Object Statistics

Although the CBO makes its decisions about how to optimize a statement using data from various sources, the majority of the important information the CBO needs comes from object statistics. Most of this chapter is dedicated to an explanation of object statistics, although we will conclude this chapter with a few short points about other sources of information that the CBO uses.

In principle, and largely in practice, the use of object statistics as the basis for optimization is ideal. For example, we need some way to distinguish a tiny configuration table with ten rows from a transactional table with terabytes of data—object ...

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