Answering queries using views

Alon Y. Levy*, Alberto O. Mendelzon, Yehoshua Sagiv

*Corresponding author for this work

Research output: Contribution to conferencePaperpeer-review

401 Scopus citations

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 languageEnglish
Pages95-104
Number of pages10
StatePublished - 1995
Externally publishedYes
EventProceedings of the 14th ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems - San Jose, CA, USA
Duration: 22 May 199525 May 1995

Conference

ConferenceProceedings of the 14th ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems
CitySan Jose, CA, USA
Period22/05/9525/05/95

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