MiniCount: Efficient Rewriting of COUNT-Queries Using Views

We present MiniCount, the first efficient sound and complete algorithm for finding maximally contained rewritings of conjunctive queries with count, using conjunctive views with count and conjunctive views without aggregation. An efficient and scalable solution to this problem yields significant benefits for data warehousing and decision support systems, as well as for powerful data integration systems.We first present a naive rewriting algorithm implicit in the recent theoretical results by Cohen et al. [5] and identify three independent sources of exponential complexity in the naive algorithm, including an expensive containment check. Then we present and discuss MiniCount and prove it sound and complete. We also present an experimental study that shows Mini- Count to be orders of magnitude faster than the naive algorithm, and to be able to scale to large numbers of views