research-article

Tractable Orders for Direct Access to Ranked Answers of Conjunctive Queries

Authors:

Nikolaos Tziavelis,

Wolfgang Gatterbauer,

Benny Kimelfeld,

Mirek RiedewaldAuthors Info & Claims

ACM Transactions on Database Systems, Volume 48, Issue 1

Article No.: 1, Pages 1 - 45

https://doi.org/10.1145/3578517

Published: 13 March 2023 Publication History

Abstract

We study the question of when we can provide direct access to the k-th answer to a Conjunctive Query (CQ) according to a specified order over the answers in time logarithmic in the size of the database, following a preprocessing step that constructs a data structure in time quasilinear in database size. Specifically, we embark on the challenge of identifying the tractable answer orderings, that is, those orders that allow for such complexity guarantees. To better understand the computational challenge at hand, we also investigate the more modest task of providing access to only a single answer (i.e., finding the answer at a given position), a task that we refer to as the selection problem, and ask when it can be performed in quasilinear time. We also explore the question of when selection is indeed easier than ranked direct access.

We begin with lexicographic orders. For each of the two problems, we give a decidable characterization (under conventional complexity assumptions) of the class of tractable lexicographic orders for every CQ without self-joins. We then continue to the more general orders by the sum of attribute weights and establish the corresponding decidable characterizations, for each of the two problems, of the tractable CQs without self-joins. Finally, we explore the question of when the satisfaction of Functional Dependencies (FDs) can be utilized for tractability and establish the corresponding generalizations of our characterizations for every set of unary FDs.

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Cited By

Tziavelis NGatterbauer WRiedewald M(2024)Ranked Enumeration for Database QueriesACM SIGMOD Record10.1145/3703922.370392453:3(6-19)Online publication date: 8-Nov-2024
https://dl.acm.org/doi/10.1145/3703922.3703924
Arenas MMerkl TPichler RRiveros C(2024)Towards Tractability of the Diversity of Query Answers: Ultrametrics to the RescueProceedings of the ACM on Management of Data10.1145/36958332:5(1-26)Online publication date: 7-Nov-2024
https://dl.acm.org/doi/10.1145/3695833
Esmailpour ASintos S(2024)Improved Approximation Algorithms for Relational ClusteringProceedings of the ACM on Management of Data10.1145/36958312:5(1-27)Online publication date: 7-Nov-2024
https://dl.acm.org/doi/10.1145/3695831

Index Terms

Tractable Orders for Direct Access to Ranked Answers of Conjunctive Queries
1. Theory of computation
  1. Computational complexity and cryptography
    1. Complexity classes
  2. Theory and algorithms for application domains
    1. Database theory
      1. Database query languages (principles)
      2. Database query processing and optimization (theory)

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cover image ACM Transactions on Database Systems

ACM Transactions on Database Systems Volume 48, Issue 1

March 2023

112 pages

ISSN:0362-5915

EISSN:1557-4644

DOI:10.1145/3585397

Editor:
Christopher Jermaine
Rice University, USA

Issue’s Table of Contents

Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than the author(s) must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from [email protected].

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Association for Computing Machinery

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Publication History

Published: 13 March 2023

Online AM: 02 January 2023

Accepted: 14 November 2022

Revised: 07 December 2021

Received: 07 December 2021

Published in TODS Volume 48, Issue 1

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Google PhD Fellowships
German Research Foundation (DFG) Project
National Science Foundation (NSF)
French government under management of Agence Nationale de la Recherche as part of the “Investissements d’avenir” program

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Cited By

Tziavelis NGatterbauer WRiedewald M(2024)Ranked Enumeration for Database QueriesACM SIGMOD Record10.1145/3703922.370392453:3(6-19)Online publication date: 8-Nov-2024
https://dl.acm.org/doi/10.1145/3703922.3703924
Arenas MMerkl TPichler RRiveros C(2024)Towards Tractability of the Diversity of Query Answers: Ultrametrics to the RescueProceedings of the ACM on Management of Data10.1145/36958332:5(1-26)Online publication date: 7-Nov-2024
https://dl.acm.org/doi/10.1145/3695833
Esmailpour ASintos S(2024)Improved Approximation Algorithms for Relational ClusteringProceedings of the ACM on Management of Data10.1145/36958312:5(1-27)Online publication date: 7-Nov-2024
https://dl.acm.org/doi/10.1145/3695831
Tziavelis NCarmeli NGatterbauer WKimelfeld BRiedewald MGeerts FNgo HSintos S(2023)Efficient Computation of Quantiles over JoinsProceedings of the 42nd ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems10.1145/3584372.3588670(303-315)Online publication date: 18-Jun-2023
https://dl.acm.org/doi/10.1145/3584372.3588670
Tian RZhang WWang FZhou JAlhudhaif AAlenezi F(2023)Cardinality estimation of activity trajectory similarity queries using deep learningInformation Sciences: an International Journal10.1016/j.ins.2023.119398646:COnline publication date: 1-Oct-2023
https://dl.acm.org/doi/10.1016/j.ins.2023.119398

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