What-If Query Processing Policy of Main-Memory OLAP System
主存OLAP系统中what-if查询处理策略

A what-if analysis can provide a more meaningful information than classical OLAP (on-line analysis processing). Multi-Scenario hypothesis upon historical data needs efficient what-if data view support. Two novel algorithms of deltaMap and pre-merge, which can greatly improve the performance of delta table algorithm with set operations, are proposed. To analyze the performance of query re-writing algorithm and delta cube algorithm under different what-if update conditions, a global performance analysis and comparison are presented in the experiment section. This paper proposes a cost model for a what-if analysis processing engine, based on different algorithms with parameters such as application scenario, what-if update rate, complexity of what-if updates, memory storage policy, cardinality of query result set etc, that can be used as a practical framework in a what-if analysis system.