Fundamentals of Database Systems by Elmasri Ramez & Navathe Shamkant

Author:Elmasri, Ramez & Navathe, Shamkant [Navathe, Shamkant]
Language: eng
Format: epub
Publisher: Addison Wesley
Published: 2011-04-29T04:00:00+00:00

In general, a B-tree node may contain additional information needed by the algorithms that manipulate the tree, such as the number of entries q in the node and a pointer to the parent node. Next, we illustrate how to calculate the number of blocks and levels for a B-tree.

Example 4. Suppose that the search field is a nonordering key field, and we construct a B-tree on this field with p = 23. Assume that each node of the B-tree is 69 percent full. Each node, on the average, will have p * 0.69 = 23 * 0.69 or approximately 16 pointers and, hence, 15 search key field values. The average fan-out fo = 16. We can start at the root and see how many values and pointers can exist, on the average, at each subsequent level:

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