Query reformulation using materialized views in data warehouse environment

Materialized views offer opportunities for significant performance gain in query evaluation by providing fast access to pi-e-computed data. The question of when and how to use a materialized view in processing agiven query is a difficult one attracting a significant amount of research. In previous works, only materialized views whose relations are contained in those of a query have been used and, as a result, certain potentially useful materialized views were excluded from consideration. Proposed in this paper are new ways of utilizing materialized views in answering a query with aggregation operations; Views including relations not referred to in the given query are utilized. We identify the conditions where a materialized view can be used in reformulating a query. Also presented are algorithms to find the most efficient reformulated query. The proposed conditions and corresponding algorithms provide significant and practical performance improvements o the data warehousing environment. 1