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|Title:||Making Queries Tractable on Big Data with Preprocessing||Authors:||Fan, Wenfei
|Issue Date:||2013||Source:||Proceedings of the VLDB Endowment, 6 (1), p. 685-696||Abstract:||A query class is traditionally considered tractable if there exists a polynomial-time (PTIME) algorithm to answer its queries. When it comes to big data, however, PTIME al- gorithms often become infeasible in practice. A traditional and e ective approach to coping with this is to preprocess data o -line, so that queries in the class can be subsequently evaluated on the data e ciently. This paper aims to pro- vide a formal foundation for this approach in terms of com- putational complexity. (1) We propose a set of -tractable queries, denoted by T0 Q, to characterize classes of queries that can be answered in parallel poly-logarithmic time (NC) after PTIME preprocessing. (2) We show that several natu- ral query classes are -tractable and are feasible on big data. (3) We also study a set TQ of query classes that can be ef- fectively converted to -tractable queries by re-factorizing its data and queries for preprocessing. We introduce a form of NC reductions to characterize such conversions. (4) We show that a natural query class is complete for TQ. (5) We also show that T0 Q P unless P = NC, i.e., the set T0 Q of all -tractable queries is properly contained in the set P of all PTIME queries. Nonetheless, TQ = P, i.e., all PTIME query classes can be made -tractable via proper re- factorizations. This work is a step towards understanding the tractability of queries in the context of big data.||Document URI:||http://hdl.handle.net/1942/15806||ISSN:||2150-8097||e-ISSN:||2150-8097||DOI:||http://www.vldb.org/pvldb/vol6/p685-geerts.pdf||Category:||A2||Type:||Journal Contribution|
|Appears in Collections:||Research publications|
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