A distributed query processing strategy using placement dependency

We present an algorithm to make use of placement dependency information to process distributed queries. Our algorithm first partitions the referenced relations of a given query into a number of non-exclusive subsets such that the fragmented relations within a subset have placement dependency and the join operation(s) associated with the relations in the subset can be locally processed without data transfer. Each subset is associated with a set of sites and can be used to generate an execution plan for the given query. It does this by keeping the fragmented relations in the subset fragmented at the sites where they are situated, while replicating the other referenced relations at each of the processing sites. Among the alternatives, our algorithm picks the plan that gives the minimum response time. Our experimental results show that our algorithm improves response time significantly.