Spatial Joins

This chapter describes algorithms, cost models and optimization techniques for spatial joins. Joins are among the most common queries in Spatial Database Management Systems. Due to their importance and high processing cost, a number of algorithms have been proposed covering all possible cases of indexed and non-indexed inputs. We first describe some popular methods for processing binary spatial joins and provide models for selectivity and cost estimation. Then, we discuss evaluation of multiway spatial joins by integrating binary algorithms and synchronous tree traversal. Going one step further, we show how analytical models can be used to combine the various join operators in optimal evaluation plans. The chapter can serve as a comprehensive reference text to the researcher who wants to learn about this important spatial query operator and to the developer who wants to include spatial query processing modules in a Database System.