Multiple-Site Distributed Spatial Query Optimization Using Spatial Semijoins

In this paper, we present our strategy for distributed spatial query optimization that involves multiple sites. Previous work in the area of distributed spatial query processing and optimization focuses only on strategies for performing spatial joins and spatial semijoins, and distributed spatial queries that only involve two sites. We propose a strategy for optimizing a distributed spatial query using spatial semijoins that can involve any number of sites in a distributed spatial database. In this initial work we focus on minimizing the data transmission cost of a distributed spatial query by identifying and initiating semijoins from the smaller relations in order to reduce the larger relations and minimize the cost of data transmission. We compare the performance of our strategy against the naïve approach of shipping entire relations to the query site. We find that our strategy minimizes the data transmission cost in all cases, and significantly in specific situations.