Multi-way Spatial Joins Using R-Trees: Methodology and Performance Evaluation

We propose a new multi-way spatial join algorithm called M-way R-tree join which synchronously traverses M R-trees. The M-way R-tree join can be considered as a generalization of the 2-way R-tree join. Although a generalization of the 2-way R-tree join has recently been studied, it did not properly take into account the optimization techniques of the original algorithm. Here, we extend these optimization techniques for M-way joins. Since the join ordering was considered to be important in the M-way join literature (e.g., relational join), we especially consider the ordering of the search space restriction and the plane sweep. Additionally, we introduce indirect predicates in the M-way join and propose a further optimization technique to improve the performance of the M-way R-tree join. Through experiments using real data, we show that our optimization techniques significantly improve the performance of the M-way spatial join.