CHAPTER 4Simple B-tree Access
In this chapter, we will examine the arithmetic the optimizer uses to calculate the cost of using a simple B-tree index to access a single table. The investigation will not be exhaustive, and will focus only on the general principles, skimming over the numerous special cases where the optimizer "tweaks" the numbers a little
I shall basically be covering range scans, including full scans and index-only scans, with a brief mention of unique scans. There are other uses of indexes, of course—we have already seen fast full scans in Chapter 2, and we will be exploring skip scans, and index joins in volumes 2 and 3
This chapter requires you to be familiar with the concept of selectivity and how the optimizer calculates ...
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