An Extended Technique for Query Reformulation using Aggregated Materialized Views

Materialized views which are stored views of the database offer opportunities for significant performance gain in query evaluation by providing fast access to pre-computed data. Whether a materialized view can be used in answering a query depends on the relationship between the view and the query. In previous works. Only one-to-one or containment mapping from views to a query has 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 “group-by” clause and aggregation. Views including relations not referred to in the given query are utilized. Attributes missing from a view can be recovered under certain conditions. We identify the conditions where a view can be used in reformulating a query and the algorithms that can effectively test these conditions and reformulate the query. The proposed conditions and corresponding algorithms provide a significant and practical extension to the usability of materialized views in query processing.