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.