On the complexity of the view-selection problem

Abstract

A commonly used technique for improving query response time over very large databases is to precompute (`materialize') frequently asked queries (`views'). The problem is to select an appropriate set of views, given a limited amount of resources. Harinarayan, Rajaraman and Ulman formalized this technique in which queries are modeled by a weighted partial order, and selecting a set of views whose materialization minimizes the average query response time is equivalent to selecting a subset of nodes of the partial order that minimizes a suitably defined cost function. Because this problem is NP-hard, the focus is on approximability and heuristics. A greedy heuristic together with a `benefit' criterion is proposed to measure its performance.