An extended query reformulation technique using materialized views

Materialized views offer opportunities for significant performance gain in query evaluation by providing fast access to pre-computed data. The question of when and how to use a materialized view in processing a given query is a difficult one attracting a significant amount of research. 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. Views including relations not referred to in an original query, which were excluded in previous works, are utilized. Attributes missing from a view can be recovered under certain conditions. We present the conditions where a view may be used in these ways and 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