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http://hdl.handle.net/1942/26385
Title: | From Relation Algebra to Semi-Join Algebra: An Approach for Graph Query Optimization | Authors: | HELLINGS, Jelle Pilachowski, Catherine L. Van Gucht, Dirk GYSSENS, Marc Wu, Yuqing |
Issue Date: | 2017 | Publisher: | ASSOC COMPUTING MACHINERY | Source: | Proceedings of the 16th international symposium on database programming languages (DBPL 2017), ASSOC COMPUTING MACHINERY, (Art N° 5) | Abstract: | Many graph query languages rely on the composition operator to navigate graphs and select nodes of interests, even though evaluating compositions of relations can be costly. Often, this need for composition can be reduced by rewriting towards queries that use semi-joins instead. In this way, the cost of evaluating queries can be significantly reduced. We study techniques to recognize and apply such rewritings. Concretely, we study the relationship between the expressive power of the relation algebras, that heavily rely on composition, and the semi-join algebras, that replace the composition operator in favor of the semi-join operators. As our main result, we show that each fragment of the relation algebras where intersection and/or difference is only used on edges (and not on complex compositions) is expressively equivalent to a fragment of the semi-join algebras. This expressive equivalence holds for node queries that evaluate to sets of nodes. For practical relevance, we exhibit constructive steps for rewriting relation algebra queries to semi-join algebra queries, and prove that these steps lead to only a well-bounded increase in the number of steps needed to evaluate the rewritten queries. In addition, on node-labeled graphs that are sibling-ordered trees, we establish new relationships among the expressive power of Regular XPath, Conditional XPath, FO-logic, and the semi-join algebra augmented with restricted fixpoint operators. | Notes: | [Hellings, Jelle; Gyssens, Marc] Hasselt Univ, Hasselt, Belgium. [Pilachowski, Catherine L.; Van Gucht, Dirk] Indiana Univ, Bloomington, IN USA. [Wu, Yuqing] Pomona Coll, Claremont, CA 91711 USA. | Document URI: | http://hdl.handle.net/1942/26385 | ISBN: | 9781450353540 | DOI: | 10.1145/3122831.3122833 | ISI #: | 000426964700005 | Rights: | © 2017 ACM. | Category: | C1 | Type: | Proceedings Paper | Validations: | ecoom 2019 |
Appears in Collections: | Research publications |
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File | Description | Size | Format | |
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dbpl2017_paper.pdf | Peer-reviewed author version | 816.61 kB | Adobe PDF | View/Open |
a5-hellings.pdf Restricted Access | Published version | 843.44 kB | Adobe PDF | View/Open Request a copy |
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