GEOMETRIC APPROACH TO PREDICATE SELECTIVITY

摘要

The disclosure relates to technology for estimating selectivity of non-join multi-column (NJMC) predicates of multi-column table (MCT) database queries is disclosed. The selectivity may be geometrically estimated by representing the full space of the MCT as one polyhedron having at least one dimension for each column of the MCT, and representing the NJMC predicate space as another polyhedron having at least one dimension for each column of a predicate space determined by applying the NJMC predicate to the MCT. Then the selectivity of the NJMC predicate may be estimated by computing a percentage of the size of the NJMC predicate space polyhedron to the size of the full space polyhedron. This more accurate estimate helps database query optimizers produce better query execution plans that utilize system resources more efficiently.