Browsing by Author "Arroyuelo, Diego"

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    Optimal Joins Using Compressed Quadtrees
    (2022) Arroyuelo, Diego; Navarro, Gonzalo; Reutter, Juan L.; Rojas-Ledesma, Javiel
    Worst-case optimal join algorithms have gained a lot of attention in the database literature. We now count several algorithms that are optimal in the worst case, and many of them have been implemented and validated in practice. However, the implementation of these algorithms often requires an enhanced indexing structure: to achieve optimality one either needs to build completely new indexes or must populate the database with several instantiations of indexes such as B+-trees. Either way, this means spending an extra amount of storage space that is typically one or two orders of magnitude more than what is required to store the raw data.
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    Optimizing RPQs over a compact graph representation
    (2024) Arroyuelo, Diego; Gomez-Brandon, Adrian; Hogan, Aidan; Navarro, Gonzalo; Rojas-Ledesma, Javiel
    We propose techniques to evaluate regular path queries (RPQs) over labeled graphs (e.g., RDF). We apply a bit-parallel simulation of a Glushkov automaton representing the query over a ring: a compact wavelet-tree-based index of the graph. To the best of our knowledge, our approach is the first to evaluate RPQs over a compact representation of such graphs, where we show the key advantages of using Glushkov automata in this setting. Our scheme obtains optimal time, in terms of alternation complexity, for traversing the product graph. We further introduce various optimizations, such as the ability to process several automaton states and graph nodes/labels simultaneously, and to estimate relevant selectivities. Experiments show that our approach uses 3-5x\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\times $$\end{document} less space, and is over 5x\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\times $$\end{document} faster, on average, than the next best state-of-the-art system for evaluating RPQs.