International Business Machines Corporation
AUTOMATED OPTIMIZATION OF NUMBER-OF-FREQUENT-VALUE DATABASE STATISTICS

Abstract:

A maintenance subsystem of a database-management system (DBMS) receives a database query that requests access to data stored in a database column. The subsystem retrieves or infers frequent-value statistics for that column, each of which specifies the number of times one distinct value is stored in the column. The statistics are partitioned into Keep and Discard clusters and, using statistical or other computational methods based on the column's data distribution, the subsystem determines an optimal number of the statistics that should be kept by the DBMS in order to minimize cost, errors, or other parameters desired by an implementer. The subsystem then directly or indirectly directs a query-optimizer component of the DBMS to consider the optimal number of frequent-value statistics when selecting an optimal data-access plan. The selected plan is then used by the DBMS's storage-manager component to access the column when servicing the received query.