Single-round multiway join algorithms first reshuffle data over many servers and then evaluate the query at hand in a parallel and communication-free way. A key question is whether a given distribution policy for the reshuffle is adequate for computing a given query, also referred to as parallel-correctness. This paper extends the study of the complexity of parallel-correctness and its constituents, parallel-soundness and parallel-completeness, to unions of conjunctive queries with and without negation. As a by-product it is shown that the containment problem for conjunctive queries with negation is coNEXPTIME-complete.
@InProceedings{geck_et_al:LIPIcs.ICDT.2016.9, author = {Geck, Gaetano and Ketsman, Bas and Neven, Frank and Schwentick, Thomas}, title = {{Parallel-Correctness and Containment for Conjunctive Queries with Union and Negation}}, booktitle = {19th International Conference on Database Theory (ICDT 2016)}, pages = {9:1--9:17}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-002-6}, ISSN = {1868-8969}, year = {2016}, volume = {48}, editor = {Martens, Wim and Zeume, Thomas}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2016.9}, URN = {urn:nbn:de:0030-drops-57787}, doi = {10.4230/LIPIcs.ICDT.2016.9}, annote = {Keywords: Conjunctive queries, distributed evaluation} }
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