Rewriting Queries Using Views with Access Patterns Under Integrity Constraints

Deutsch, Alin; Ludäscher, Bertram; Nash, Alan

doi:10.1007/978-3-540-30570-5_24

Cited by 49 publications

(66 citation statements)

References 20 publications

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“…In [2], a run-time optimization technique, that exploits the information about database dependencies that hold on the sources, is presented; [5] uses the structure of the query to minimize the accesses needed to retrieve all obtainable answers to a query. [9] solves the (quite general) problem of query answering using views [13] under integrity constraints and under access limitations by reducing it to the same problem under integrity constraints only; various extensions to the query languages are provided. In [20], the authors analyze the complexity of determining the feasibility of a query, i.e., determining whether there exists an equivalent query that is executable as is, while respecting the access limitations.…”

Section: Related Workmentioning

confidence: 99%

Conjunctive Query Containment under Access Limitations

Calì

Martinenghi

2008

Lecture Notes in Computer Science

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Abstract. Access limitations may occur when querying data sources over the web or heterogeneous data sources presented as relational tables: this happens, for instance, in Data Exchange and Integration, Data Warehousing, and Web Information Systems. Access limitations force certain attributes to be selected in order to access the tables. It is known that evaluating a conjunctive query under such access restrictions amounts to evaluating a possibly recursive Datalog program. We address the problem of checking containment of conjunctive queries under access limitations, which is highly relevant in query optimization. Checking containment in such a setting would amount to checking containment of recursive Datalog programs of a certain class, while, for general Datalog programs, this problem is undecidable. We propose a decision procedure for query containment based on the novel notion of crayfish-chase, showing that containment can be decided in co-nexptime, which improves upon the known bound of 2exptime. Moreover, by means of a direct proof, our technique provides a new insight into the structure of the problem.

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Section: Related Workmentioning

confidence: 99%

Conjunctive Query Containment under Access Limitations

Calì

Martinenghi

2008

Lecture Notes in Computer Science

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“…In this paper we focus on those problem settings where one is to find a rewriting of a given CQAC query in terms of given CQAC views, but an equivalent UCQAC rewriting does not exist, and thus the algorithm of [9] returns no answer. Further, Deutsch, Ludaescher, and Nash [16] provided approaches for solving the problem of rewriting queries using views with limited access patterns under integrity constraints, focusing on queries, views, and constraints over unions of conjunctive queries with negation. We comment on the contributions of [16] w.r.t.…”

Section: Let Q() :-P(a B) a ≤ B; V () :-P(x Y ) P(y X); And R() mentioning

confidence: 99%

“…Further, Deutsch, Ludaescher, and Nash [16] provided approaches for solving the problem of rewriting queries using views with limited access patterns under integrity constraints, focusing on queries, views, and constraints over unions of conjunctive queries with negation. We comment on the contributions of [16] w.r.t. the algorithms that we propose in this paper when discussing our specific contributions.…”

Section: Let Q() :-P(a B) a ≤ B; V () :-P(x Y ) P(y X); And R() mentioning

confidence: 99%

“…5 The size-limit restriction of Build-MaxCR is due to the fact that for CQAC queries and views, a view-based UCQAC MCR may have an unbounded number of CQAC disjuncts, see Example 2. To the best of our knowledge, the approaches of [16] do not provide for constructing size-limited contained rewritings of the input queries using views, which are addressed by our algorithm Build-MaxCR. 2.…”

Section: Let Q() :-P(a B) a ≤ B; V () :-P(x Y ) P(y X); And R() mentioning

confidence: 99%

“…In such scenarios, users might be interested in containing rewritings, which return a superset of the set of the query answers. Minimally containing rewritings (MiCRs) [16,17,18] are the containing rewritings that return the fewest false positives when answering the query.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Approximate Rewriting of Queries Using Views

Afrati

Chandrachud

Chirkova

et al. 2009

Advances in Databases and Information Systems

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Abstract. We study approximate, that is contained and containing, rewritings of queries using views. We consider conjunctive queries with arithmetic comparisons (CQACs), which capture the full expressive power of SQL select-project-join queries. For contained rewritings, we present a sound and complete algorithm for constructing, for CQAC queries and views, a maximally-contained rewriting (MCR) whose all CQAC disjuncts have up to a predetermined number of view literals. For containing rewritings, we present a sound and efficient algorithm pruned-MiCR, which computes a CQAC containing rewriting that does not contain any other CQAC containing rewriting (i.e., computes a minimally containing rewriting, MiCR) and that has the minimum possible number of relational subgoals. As a result, the MiCR rewriting produced by our algorithm may be very efficient to execute. Both algorithms have good scalability and perform well in many practical cases, due to their extensive pruning of the search space, see [1].

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Chase

Deutsch¹,

Nash²

2009

Encyclopedia of Database Systems

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Rewriting Queries Using Views with Access Patterns Under Integrity Constraints

Cited by 49 publications

References 20 publications

Conjunctive Query Containment under Access Limitations

Conjunctive Query Containment under Access Limitations

Approximate Rewriting of Queries Using Views

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