Abstract
We consider the problem of computing answers to queries by using materialized views. Aside from its potential in optimizing query evaluation, the problem also arises in applications such as Global Information Systems, Mobile Computing and maintaining physical data independence. We consider the problem of finding a rewriting of a query that uses the materialized views, the problem of finding minimal rewritings, and finding complete rewritings (i.e., rewritings that use only the views). We show that all the possible rewritings can be obtained by considering containment mappings from the views to the query, and that the problems we consider are NP-complete when both the query and the views are conjunctive and don't involve built-in comparison predicates. We show that the problem has two independent sources of complexity (the number of possible containment mappings, and the complexity of deciding which literals from the original query can be deleted). We describe a polynomial time algorithm for finding rewritings, and show that under certain conditions, it will find the minimal rewriting. Finally, we analyze the complexity of the problems when the queries and views may be disjunctive and involve built-in comparison predicates.
Original language | English |
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Pages | 95-104 |
Number of pages | 10 |
State | Published - 1995 |
Externally published | Yes |
Event | Proceedings of the 14th ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems - San Jose, CA, USA Duration: 22 May 1995 → 25 May 1995 |
Conference
Conference | Proceedings of the 14th ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems |
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City | San Jose, CA, USA |
Period | 22/05/95 → 25/05/95 |