Data Virtualization for Business Intelligence Systems

Chapter 6

Data Virtualization ServerQuery Optimization Techniques

6.1 Introduction

This is the last of four chapters that discuss the internals of data virtualization servers. Chapter 5 describes caching as a technique to improve the performance of queries. This chapter is devoted to the second technique called query optimization. This is the process of determining the best processing strategy for a query. Various techniques can be deployed by data virtualization servers for optimizing the queries entered by data consumers.

When working with languages such as SQL, MDX, XSLT, and XQuery, developers only have to specify what data they want. They don’t have to indicate how data should be retrieved from the data stores. That’s why they are sometimes ...