Abstract: A method, apparatus, and computer instructions for selecting and recommending of clustering indexes are provided. Baseline run time cost estimates are calculated based on database designs. Workload benefit of a candidate clustering design is calculated and compared to the baseline costs. If the workload benefit outweighs the baseline costs, clustering dimension solutions originated from the record identifier (RID) based index are identified. A clustering design is selected based on the identified clustering dimension solutions and the total number of recommended clustering dimensions for a given table. Based on the number of dimensions observed, either a multidimensional clustering solution or a RID based clustering index is recommended.

Abstract: A method executed by a data processor for scanning a reverse range. The scan is conducted in an index for a table having an upper end and a lower end. The reverse range has a start key value for defining the reverse range, and the index has a set of keys representing a set of records and record attributes in the table. Each key in the set of keys has a RID designating a record in the table and a key value corresponding to an attribute of the record in the table. The method includes the steps of searching the index for a start key, selecting an upper bound of the reverse range, and, if the upper bound is the first key in the index, indicating that the index does not contain any key value within the reverse range, or, if the upper bound is not the first key in the index, then fetching each key below the upper bound in the index.