Optimal column layout for hybrid workloads

Data-intensive analytical applications need to support both efficient reads and writes. However, what is usually a good data layout for an update-heavy workload, is not well-suited for a read-mostly one and vice versa. Modern analytical data systems rely on columnar layouts and employ delta stores to inject new data and updates. We show that for hybrid workloads we can achieve close to one order of magnitude better performance by tailoring the column layout design to the data and query workload. Our approach navigates the possible design space of the physical layout: it organizes each column’s data by determining the number of partitions, their corresponding sizes and ranges, and the amount of buffer space and how it is allocated. We frame these design decisions as an optimization problem that, given workload knowledge and performance requirements, provides an optimal physical layout for the workload at hand. To evaluate this work, we build an in-memory storage engine, Casper, and we show that it outperforms state-of-the-art data layouts of analytical systems for hybrid workloads. Casper delivers up to 2.32x higher throughput for update-intensive workloads and up to 2.14x higher throughput for hybrid workloads. We further show how to make data layout decisions robust to workload variation by carefully selecting the input of the optimization.http://www.vldb.org/pvldb/vol12/p2393-athanassoulis.pdfPublished versionPublished versio

Market access and seaport efficiency: the case of container handling in Norway

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/Comprehensive studies on the impact of market access on port efficiency are scarce, and the problem that market access indicators are potentially endogenous lacks treatment in maritime economics. This paper offers both theoretical and empirical advances to fill these research gaps. First, it pioneers in the use of Stochastic semi-Nonparametric Envelopment of Z variables Data for measuring port efficiency, and further develops the methodology for panel data and proposes an instrumental variable extension for dealing with endogenous market access indicators. Second, it advances the empirical port literature by developing a unique panel dataset on Norwegian container ports encompassing a comprehensive set of foreland and hinterland connectivity measures. Our comprehensive assessment suggests that the role of market access in determining port efficiency is uncertain.Market access and seaport efficiency: the case of container handling in NorwaypublishedVersio

Employee perceived effect of leadership training: comparing public and private organizations

This study reports on the effectiveness of a year-long field experiment involving training in transformational and transactional leadership in the public and private sectors. Using before and after training assessments by employees of several hundred Danish leaders, the analysis shows that transformational leadership training is associated with increases in behaviors linked to both transformational leadership and the use of verbal rewards, but only for public sector organizations. There is no impact in private sector organizations. Transactional leadership training appears to be equally effective in stimulating the use of pecuniary rewards in both public and private organizations

GroupFinder: A New Approach to Top-K Point-of-Interest Group Retrieval

The notion of point-of-interest (PoI) has existed since paper road maps began to include markings of useful places such as gas stations, hotels, and tourist attractions. With the introduction of geopositioned mobile devices such as smartphones and mapping services such as Google Maps, the retrieval of PoIs relevant to a user’s intent has became a problem of automated spatio-textual information retrieval. Over the last several years, substantial research has gone into the invention of functionality and efficient implementations for retrieving nearby PoIs. However, with a couple of exceptions existing proposals retrieve results at single-PoI granularity. We assume that a mobile device user issues queries consisting of keywords and an automatically supplied geo-position, and we target the common case where the user wishes to find nearby groups of PoIs that are relevant to the keywords. Such groups are relevant to users who wish to conveniently explore several options before making a decision such as to purchase a specific product. Specifically, we demonstrate a practical proposal for finding top-k PoI groups in response to a query. We show how problem parameter settings can be mapped to options that are meaningful to users. Further, although this kind of functionality is prone to combinatorial explosion, we will demonstrate that the functionality can be supported efficiently in practical settings. 1

Seeing eye to eye: can leadership training align perceptions of leadership?

There is a huge gap between how employees see leaders' behavior and how leaders see themselves regardless of sector and functional area. Because this gap can be a serious problem in managing organizations, scholars have investigated how the gap can be reduced. This article focuses on leadership training and tests whether and under what conditions it narrows the gap. Using quantitative and qualitative data from a randomized field experiment with several hundred Danish leaders from public and private organizations, we find that a yearlong leadership training course decreases the differences between leader and employee perceptions of transformational and transactional leadership behaviors in public sector organizations but not in private organizations. The findings imply that leadership training can be one way for public organizations to align perceptions of leadership.18 month embargo; published online: 30 June 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]