Bypassing Joins in Disjunctive Queries
Michael Steinbrunn, Klaus Peithner, Guido Moerkotte, Alfons Kemper · MADOC (University of Mannheim) · 1995
In this paper we develop a novel optimization strategy for disjunctive queries involving join predicates. This work is an extension of our previously published approach [KMPS94] for optimizing disjunctive selection predicates by generating two output streams from selection operators: a "true"-stream for objects (tuples) satisfying the selection predicate and a "false"-stream for those objects not satisfying the predicate. Then, each stream undergoes an individual, "customized" optimization. Here, we extend the basic idea of [KMPS94] to disjunctive queries with join operators. Analogously to selections, we propose to generate two output streams from a join operator: one "true"-stream for pairs of objects (of the two input streams) that satisfy the join predicate and one "false"- stream for those pairs not satisfying it. In combination with the extended selection predicate processing, this provides a large potential for efficiently evaluating disjunctive queries because it allows to "byp...