Conjunctive query containment revisited: Extended Abstract

Chandra Chekuri, Anand Rajaraman

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We consider the problems of conjunctive query containment and minimization, which are known to be NP-complete, and show that these problems can be solved in polynomial time for the class of acyclic queries. We then generalize the notion of acyclicity and define a parameter called query width that captures the “degree of cyclicity” of a query: in particular, a query is acyclic if and only if its query width is 1. We give algorithms for containment and minimization that run in time polynomial in nk, where n is the input size and k is the query width. These algorithms naturally generalize those for acyclic queries, and are of practical significance because many queries have small query width compared to their sizes. We show that we can obtain good bounds on the query width of Q using the treewidth of the incidence graph of Q. Finally, we apply our containment algorithm to the practically important problem of finding equivalent rewritings of a query using a set of materialized views.

Original languageEnglish (US)
Title of host publicationDatabase Theory - ICDT 1997 - 6th International Conference, Proceedings
EditorsFoto Afrati, Phokion Kolaitis
Number of pages15
ISBN (Print)9783540622222
StatePublished - 1997
Externally publishedYes
Event6th International Conference on Database Theory, ICDT 1997 - Delphi, Greece
Duration: Jan 8 1997Jan 10 1997

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other6th International Conference on Database Theory, ICDT 1997

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Computer Science(all)


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