Early Separation of Filter and Refinement Steps in Spatial Query Optimization

The spatial query has been processed in two steps, the filter step and the refinement step, due to a large volume and high complexity of the spatial data. However, this approach has been considered only in the query execution phase after completing the query optimization phase. This paper presents query optimization strategies which take the characteristics of spatial databases into account. The first strategy is the separation of filter and refinement steps not in the query execution phase but in the query optimization phase. As the second strategy, several refinement operations can be combined in processing a complex query, and as the third strategy several filter operations can also be combined. We call the optimization technique utilizing these strategies the Early Separated Filter And Refinement (ESFAR). This paper also presents a rule-based optimization technique for ESFAR.