Complete and Equivalent Query Rewriting Using Views

Query rewriting using views is a technique for answering a query using a set of views instead of accessing the database relations directly. There are two categories of rewritings, i.e., equivalent rewriting using materialized views applied in query optimization, and maximally contained rewriting used in data integration. Although maximally contained rewriting is acceptable in data integration, there are cases where an equivalent rewriting is desired. More importantly, the maximally contained rewriting is a union of all the contained queries, many of which are redundant. This thesis gives an efficient algorithm to find a complete and equivalent rewriting that is a single conjunctive query. We proved that the algorithm is guaranteed to find all the complete and equivalent rewritings, and that the produced rewriting is guarantee to be equivalent without additional containment checking. We showed that our algorithm is much faster than other algorithms by complexity analysis and experiments.