| | |
Summary: Accurate Estimation of the Cost of Spatial Selections
Ashraf Aboulnaga Jeffrey F. Naughton
Computer Sciences Department
University of Wisconsin - Madison
{ashraf,naughton}@cs.wisc.edu
Abstract
Optimizing queries that involve operations on spatial data
requires estimating the selectivity and cost of these oper-
ations. In this paper, we focus on estimating the cost of
spatial selections, or window queries, where the query win-
dows and data objects are general polygons. Cost estima-
tion techniques previously proposed in the literature only
handle rectangular query windows over rectangular data
objects, thus ignoring the very significant cost of exact ge-
ometry comparison (the refinement step in a "filter and re-
fine" query processing strategy). The cost of the exact ge-
ometry comparison depends on the selectivity of the filtering
step and the average number of vertices in the candidate
objects identified by this step. In this paper, we introduce
a new type of histogram for spatial data that captures the
|
