License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.ICDT.2019.23
URN: urn:nbn:de:0030-drops-103252
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2019/10325/
Koutris, Paraschos ;
Wijsen, Jef
Consistent Query Answering for Primary Keys in Logspace
Abstract
We study the complexity of consistent query answering on databases that may violate primary key constraints. A repair of such a database is any consistent database that can be obtained by deleting a minimal set of tuples. For every Boolean query q, CERTAINTY(q) is the problem that takes a database as input and asks whether q evaluates to true on every repair. In [Koutris and Wijsen, ACM TODS, 2017], the authors show that for every self-join-free Boolean conjunctive query q, the problem CERTAINTY(q) is either in P or coNP-complete, and it is decidable which of the two cases applies. In this paper, we sharpen this result by showing that for every self-join-free Boolean conjunctive query q, the problem CERTAINTY(q) is either expressible in symmetric stratified Datalog (with some aggregation operator) or coNP-complete. Since symmetric stratified Datalog is in L, we thus obtain a complexity-theoretic dichotomy between L and coNP-complete. Another new finding of practical importance is that CERTAINTY(q) is on the logspace side of the dichotomy for queries q where all join conditions express foreign-to-primary key matches, which is undoubtedly the most common type of join condition.
BibTeX - Entry
@InProceedings{koutris_et_al:LIPIcs:2019:10325,
author = {Paraschos Koutris and Jef Wijsen},
title = {{Consistent Query Answering for Primary Keys in Logspace}},
booktitle = {22nd International Conference on Database Theory (ICDT 2019)},
pages = {23:1--23:19},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-101-6},
ISSN = {1868-8969},
year = {2019},
volume = {127},
editor = {Pablo Barcelo and Marco Calautti},
publisher = {Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
address = {Dagstuhl, Germany},
URL = {http://drops.dagstuhl.de/opus/volltexte/2019/10325},
doi = {10.4230/LIPIcs.ICDT.2019.23},
annote = {Keywords: conjunctive queries, consistent query answering, Datalog, primary keys}
}
Keywords: |
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conjunctive queries, consistent query answering, Datalog, primary keys |
Collection: |
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22nd International Conference on Database Theory (ICDT 2019) |
Issue Date: |
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2019 |
Date of publication: |
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19.03.2019 |