Performance Tuning - Question 110

What is the main reason to create a reverse key index on a column?

A. The column is populates using a sequence.

B. The column contains many different values.

C. The column is mainly used for value range scans.

D. The column implementing an inverted list attribute.

Answer: A

Explanation:

The Reverse Key Index (RKI) is a special type of B-Tree index. The RKI is useful when an index is built on a column that contains sequential numbers.

Incorrect Answers

B: B-Tree index will be appropriate choice for the column with many different values.

C: The column is mainly used for value range scans is not good candidate for the Reverse Key Index. Reverse Key indexes are only useful for equality and non-equality searches. Queries that perform range scans (e.g., using BETWEEN, >, <) on columns that are Reverse Key indexed will not be able to use the index and will cause full table scans.

D: The RKI does not work for the column implementing an inverted list attribute.

OCP: Oracle 9i Performance Tuning Study Guide, Joseph C. Johnson, p. 156-158

Chapter 3: SQL Application Tuning and Design