A Strategy for Optimizing a Multi-site Query in a Distributed Spatial Database

Abstract

In this paper, we present a novel strategy for distributed spatial query optimization that involves multiple sites. Most 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 new strategy, called the Restricted strategy, for optimizing a distributed spatial query. It uses spatial semijoins and can involve any number of sites in a distributed spatial database. The Restricted strategy improves upon an existing strategy by sending group approximations, instead of sending approximations for all objects, in order to reduce the number of comparisons between objects and thereby minimize the CPU and data transmission cost. A performance evaluation of our strategy finds that it significantly minimizes the number of data comparisons and CPU time of distributed spatial queries.