Dynamic caching of query results for decision support systems

The response time of DSS (decision support system) queries is typically several orders of magnitude higher than the response time of OLTP (online transaction processing) queries. Since DSS queries are often submitted interactively, techniques for reducing their response time are becoming increasingly important. We argue that caching of query results is one such technique particularly well suited to the DSS environment. We have designed a query cache manager for such an environment. The cache manager can lookup query results from the cache either based on an exact query match or using a query split algorithm to efficiently find query results which subsume the submitted query. The cache manager dynamically maintains the cache content by deciding whether a newly generated query result should be admitted to the cache and if so, which query results should be evicted from the cache to free space for the new query result. The decisions are aimed at minimizing the query response time. The decisions are explicitly based on a cost function that considers the execution cost of each query, the size of each query result, the reference frequency to each result, the cost of maintenance of each result due to updates of the base tables, and the frequency of such updates. Experimental evaluation shows that our cache manager can improve performance on TPC-D like workloads.