Bucket-Based Query Rewriting with Disjunctive Data Source

Many algorithms for query rewriting using views have been proposed. Most of them are used for rewriting conjunctive queries with conjunctive views only. Only one inverse rule-based rewriting algorithm has been presented to deal with query rewriting with disjunctive views, in which a set of disjunctive inverse rules are created and used to generate the query rewritings. However, there has no been bucket-based algorithm for this issue. In this paper we apply the ideas of the previous bucket-based algorithms to deal with query rewriting using views in the presence of disjunctions in view definitions. We create a set of buckets over either a conjunctive view or a disjunctive view. Specially, when a bucket is over a disjunctive view, we present a method to remove the tuples that are in the view but not required by a given query. The rewritings obtained by our algorithm are contained in the original query.