is prohibited.
Section III
Efficiency of
Analytical Processing
6 Karayannidis, Tsois, & Sellis
Copyright ?© 2007, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of
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Chapter.VI
Advanced.Ad.Hoc.Star.
Query.Processing
Nikos Karayannidis
National Technical University of Athens, Greece
Aris Tsois
National Technical University of Athens, Greece
Timos Sellis
National Technical University of Athens, Greece
Abstract
Star queries are the most prevalent kind of queries in data warehousing, online
analytical processing (OLAP), and business intelligence applications. Thus, there
is an imperative need for efficiently processing star queries. To this end, a new class
of fact table organizations has emerged that exploits path-based surrogate keys in
order to hierarchically cluster the fact table data of a star schema. In the context
of these new organizations, star query processing changes radically. In this chapter,
we present a complete abstract processing plan that captures all the necessary
steps in evaluating such queries over hierarchically clustered fact tables. Furthermore,
we realize the abstract operations in terms of physical operations over the
CUBE File data structure. Finally we discuss star query optimization issues over
the presented abstract plan.
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