Forecasting the cost of processing multi-join queries via hashing for main-memory databases (Extended version)

Database management systems (DBMSs) carefully optimize complex multi-join queries to avoid expensive disk I/O. As servers today feature tens or hundreds of gigabytes of RAM, a significant fraction of many analytic databases becomes memory-resident. Even after careful tuning for an in-memory environment, a linear disk I/O model such as the one implemented in PostgreSQL may make query response time predictions that are up to 2X slower than the optimal multi-join query plan over memory-resident data. This paper introduces a memory I/O cost model to identify good evaluation strategies for complex query plans with multiple hash-based equi-joins over memory-resident data. The proposed cost model is carefully validated for accuracy using three different systems, including an Amazon EC2 instance, to control for hardware-specific differences. Prior work in parallel query evaluation has advocated right-deep and bushy trees for multi-join queries due to their greater parallelization and pipelining potential. A surprising finding is that the conventional wisdom from shared-nothing disk-based systems does not directly apply to the modern shared-everything memory hierarchy. As corroborated by our model, the performance gap between the optimal left-deep and right-deep query plan can grow to about 10X as the number of joins in the query increases.Comment: 15 pages, 8 figures, extended version of the paper to appear in SoCC'1

Improving Primo Usability and Teachability with Help from the Users

In the aftermath of a consortium migration to a shared cloud-based resource management and discovery system, a small college library implemented a web usability test to uncover the kinds of difficulties students had with the new interface. Lessons learned from this study led to targeted changes, which simplified aspects of searching, but also enhanced the librarians’ ability to teach more effectively. The authors discuss the testing methods, results, and teaching opportunities, both realized and potential, which arose from implementing changes

Collaborative yet independent: Information practices in the physical sciences

In many ways, the physical sciences are at the forefront of using digital tools and methods to work with information and data. However, the fields and disciplines that make up the physical sciences are by no means uniform, and physical scientists find, use, and disseminate information in a variety of ways. This report examines information practices in the physical sciences across seven cases, and demonstrates the richly varied ways in which physical scientists work, collaborate, and share information and data. This report details seven case studies in the physical sciences. For each case, qualitative interviews and focus groups were used to understand the domain. Quantitative data gathered from a survey of participants highlights different information strategies employed across the cases, and identifies important software used for research. Finally, conclusions from across the cases are drawn, and recommendations are made. This report is the third in a series commissioned by the Research Information Network (RIN), each looking at information practices in a specific domain (life sciences, humanities, and physical sciences). The aim is to understand how researchers within a range of disciplines find and use information, and in particular how that has changed with the introduction of new technologies

Meetings, Weedings, Development.. Oh My!

Hello!! Since the last time I posted a lot has happened and so far, still good. That’s not to say I haven’t needed help on a few Reference Questions but things are going pretty well. I’ve had a few ‘RefWins’ where I’ve felt that I was particularly helpful, one was even over chat! Everything is going great thus far and I’m definitely learning, a lot. [excerpt

Merge Everything It Makes Sense to Merge: The History and Philosophy of the Merged Reference Collection at the Dr. Martin Luther King, Jr. Library in San Jose, California

The Dr. Martin Luther King, Jr. Library in San Jose, California is a unique dual-use library serving the students of San Jose State University and the community of San Jose, California. The reference collections of the two libraries are merged and interfiled to promote ease of access for both populations served. Economies of scale were realized through collaborative collection development activities for major reference purchases between the two institutions. This article describes the planning and creation of the King Library\u27s merged reference collection and reviews the literature of collaborative collection development and merged or interfiled collections

Encore EDS Task Force Final Summary Report (6.4.14)

Final report of the Encore EDS Task Force recommending that, After careful consideration, trial and evaluation, the task force reached consensus that HELIN should move forward in switching from Serials Solutions to EBSCO\u27s A-Z with LinkSource product for 2014-2015. This will allow each HELIN library to decide for themselves whether to start using Encore Duet immediately, or to hold off until upcoming enhancements become available. In order to be ready for the beginning of the 2014 fall semester, the task force recommends that the transition to EBSCO A to Z with Linksource be made as soon as possible and that the HELIN Board and Central Office communicate a timeline for implementation of EBSCO A to Z with Linksource and Encore Duet to the HELIN Libraries

An open reply to "What is going on at the Library of Congress?" by Thomas Mann

This is an open response to a report by Thomas Mann at the Library of Congress concerning changes in cataloging. The author contends that, although the current changes at the Library of Congress are suspect, changes are imminent and experienced catalogers must offer positive suggestions for change, otherwise they will be ignored by management