Abstract: Techniques for making aggregated entries in a database table which aggregate information from other entries in tables in the database system. The techniques permit the aggregated entries to contain not only metric values aggregated from the other entries by techniques such as averaging in which the individual values are lost, but also sets of individual values from the other entries. One area of application for the techniques is the roll up tables used in the management systems for database management systems to reduce the size of historic information about events that have occurred in the database management system. Each roll up entry in a roll up table is an aggregated entry that contains information about some number of events. A roll up entry that uses the techniques contains a representation of a set whose values are the occurrence times of the events that are represented by the rollup record.

Abstract: A method evaluates a plurality of candidate index sets for a workload of database statements in a database system by first generating baseline statistics for each statement in the workload. An index superset is formed by combining an existing or current index set and a proposed index set. A candidate index set is derived from the index superset, the candidate index being one of the plurality of candidate index sets. Statistics for a statement are generated by first creating an execution plan which represents an efficient series of steps for executing the statement given the candidate index set. The execution plan is evaluated, and statistics based on the evaluation of the execution plan are generated and recorded. The cost of the execution plan is then determined and statistics are generated. Statistics for each candidate index set are rolled up and presented to a user or an index tuning mechanism.